UEU-co logo

5.htm

Chapter 5 The Abdomen: Part II—The Abdominal Cavity A 15-year-old boy complaining of pain in the lower right part of the anterior abdominal wall was seen by a physician. On examination, he was found to have a temperature of 101°F (38.3°C). He had a furred tongue and was extremely tender in the lower right quadrant. The abdominal muscles in that area were found to be firm (rigid) on palpation and became more spastic when increased pressure was applied (guarding). A diagnosis of acute appendicitis was made. Inflammation of the appendix initially is a localized disease giving rise to pain that is often referred to the umbilicus. Later, the inflammatory process spreads to involve the peritoneum covering the appendix, producing a localized peritonitis. If the appendix ruptures, further spread occurs and a more generalized peritonitis is produced. Inflammation of the peritoneum lining the anterior abdominal wall (parietal peritoneum) causes pain and reflex spasm of the anterior abdominal muscles. This can be explained by the fact that the parietal peritoneum, the abdominal muscles, and the overlying skin are supplied by the same segmental nerves. This is a protective mechanism to keep that area of the abdomen at rest so that the inflammatory process remains localized. The understanding of the symptoms and signs of appendicitis depends on having a working knowledge of the anatomy of the appendix, including its nerve supply, blood supply, and relationships with other abdominal structures. Chapter Objectives

  • The abdominal cavity contains many vital organs, including the gastrointestinal tract, liver, biliary ducts, pancreas, spleen, and parts of the urinary system. These structures are closely packed within the abdominal cavity, and therefore disease of one can easily involve another. Gastrointestinal tract inflammation and bleeding, malignant disease, and penetrating trauma to the abdomen are just some of the problems facing the physician.
  • Emergency problems involving the urinary system are common and may present diverse symptoms ranging from excruciating pain to failure to void urine.
  • Within the abdomen also lie the aorta and its branches, the inferior vena cava and its tributaries, and the important portal vein.
  • The purpose of this chapter is to give the student an understanding of the significant anatomy relative to clinical problems. Examiners can ask many good questions regarding this region.

P.202
P.203
Basic Anatomy General Arrangement of the Abdominal Viscera Liver The liver is a large organ that occupies the upper part of the abdominal cavity (Figs. 5-1 and 5-2). It lies almost entirely under cover of the ribs and costal cartilages and extends across the epigastric region. Gallbladder The gallbladder is a pear-shaped sac that is adherent to the undersurface of the right lobe of the liver; its blind end, or fundus, projects below the inferior border of the liver (Figs. 5-1 and 5-2). Esophagus The esophagus is a tubular structure that joins the pharynx to the stomach. The esophagus pierces the diaphragm slightly to the left of the midline and after a short course of about 0.5 in. (1.25 cm) enters the stomach on its right side. It is deeply placed, lying behind the left lobe of the liver (Fig. 5-1). Stomach The stomach is a dilated part of the alimentary canal between the esophagus and the small intestine (Figs. 5-1 and 5-2). It occupies the left upper quadrant, epigastric, and umbilical regions, and much of it lies under cover of the ribs. Its long axis passes downward and forward to the right and then backward and slightly upward. P.204

Figure 5-1 General arrangement of abdominal viscera.
Figure 5-2 Abdominal organs in situ. Note that the greater omentum hangs down in front of the small and large intestines.

Small Intestine The small intestine is divided into three regions: duodenum, jejunum, and ileum. The duodenum is the first part of the small intestine, and most of it is deeply placed on the posterior abdominal wall. It is situated in the epigastric and umbilical regions. It is a C-shaped tube that extends from the stomach around the head of the pancreas to join the jejunum (Fig. 5-1). About halfway down its length the small intestine receives the bile and the pancreatic ducts. The jejunum and ileum together measure about 20 ft (6 m) long; the upper two fifths of this length make up the jejunum. The jejunum begins at the duodenojejunal junction, and the ileum ends at the ileocecal junction (Fig. 5-1). The coils of jejunum occupy the upper left part of the abdominal cavity, whereas the ileum tends to occupy the lower right part of the abdominal cavity and the pelvic cavity (Fig. 5-3). Large Intestine The large intestine is divided into the cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal (Fig. 5-1). The large intestine arches around and encloses the coils of the small intestine (Fig. 5-3) and tends to be more fixed than the small intestine. The cecum is a blind-ended sac that projects downward in the right iliac region below the ileocecal junction (Figs. 5-1 and 5-3). The appendix is a worm-shaped tube that arises from its medial side (Fig. 5-1). The ascending colon extends upward from the cecum to the inferior surface of the right lobe of the liver, occupying the right lower and upper quadrants (Figs. 5-1 and 5-3). On reaching the liver, it bends to the left, forming the right colic flexure. The transverse colon crosses the abdomen in the umbilical region from the right colic flexure to the left colic flexure (Figs. 5-1 and 5-3). It forms a wide U-shaped curve. In the erect position, the lower part of the U may extend down into the pelvis. The transverse colon, on reaching the region of the spleen, bends downward, forming the left colic flexure to become the descending colon. The descending colon extends from the left colic flexure to the pelvis below (Figs. 5-1 and 5-3). It occupies the left upper and lower quadrants. The sigmoid colon begins at the pelvic inlet, where it is a continuation of the descending colon (Fig. 5-1). It hangs down into the pelvic cavity in the form of a loop. It joins the rectum in front of the sacrum. The rectum occupies the posterior part of the pelvic cavity (Fig. 5-1). It is continuous above with the sigmoid colon and descends in front of the sacrum to leave the pelvis by piercing the pelvic floor. Here, it becomes continuous with the anal canal in the perineum. P.205

Figure 5-3 Abdominal contents after the greater omentum has been reflected upward. Coils of small intestine occupy the central part of the abdominal cavity, whereas ascending, transverse, and descending parts of the colon are located at the periphery.

Pancreas The pancreas is a soft, lobulated organ that stretches obliquely across the posterior abdominal wall in the epigastric region (Fig. 5-4). It is situated behind the stomach and extends from the duodenum to the spleen. Spleen The spleen is a soft mass of lymphatic tissue that occupies the left upper part of the abdomen between the stomach and the diaphragm (Fig. 5-4). It lies along the long axis of the 10th left rib. Kidneys The kidneys are two reddish brown organs situated high up on the posterior abdominal wall, one on each side of the vertebral column (Fig. 5-4). The left kidney lies slightly higher than the right (because the left lobe of the liver is smaller than the right). Each kidney gives rise to a ureter that runs vertically downward on the psoas muscle. Suprarenal Glands The suprarenal glands are two yellowish organs that lie on the upper poles of the kidneys (Fig. 5-4) on the posterior abdominal wall. Peritoneum General Arrangement The peritoneum is a thin serous membrane that lines the walls of the abdominal and pelvic cavities and clothes the viscera (Figs. 5-5 and 5-6). The peritoneum can be regarded as a balloon against which organs are pressed from outside. The parietal peritoneum lines the walls of the abdominal and pelvic cavities, and the visceral peritoneum covers the organs. The potential space between the parietal and visceral layers, which is in effect the inside space of the balloon, is called the peritoneal cavity. In males, this is a closed cavity, but in females, there is communication with the exterior through the uterine tubes, the uterus, and the vagina. P.206

Figure 5-4 Structures situated on the posterior abdominal wall behind the stomach.

Between the parietal peritoneum and the fascial lining of the abdominal and pelvic walls is a layer of connective tissue called the extraperitoneal tissue; in the area of the kidneys this tissue contains a large amount of fat, which supports the kidneys. The peritoneal cavity is the largest cavity in the body and is divided into two parts: the greater sac and the lesser sac (Fig. 5-5 and 5-6). The greater sac is the main compartment and extends from the diaphragm down into the pelvis. The lesser sac is smaller and lies behind the stomach. The greater and lesser sacs are in free communication with one another through an oval window called the opening of the lesser sac, or the epiploic foramen (Figs. 5-5 and 5-7). The peritoneum secretes a small amount of serous fluid, the peritoneal fluid, which lubricates the surfaces of the peritoneum and allows free movement between the viscera. Intraperitoneal and Retroperitoneal Relationships The terms intraperitoneal and retroperitoneal are used to describe the relationship of various organs to their peritoneal covering. An organ is said to be intraperitoneal when it is almost totally covered with visceral peritoneum. The stomach, jejunum, ileum, and spleen are good examples of intraperitoneal organs. Retroperitoneal organs lie behind the peritoneum and are only partially covered with visceral peritoneum. The pancreas and the ascending and descending parts of the colon are examples of retroperitoneal organs. No organ, however, is actually within the peritoneal cavity. An intraperitoneal organ, such as the stomach, appears to be surrounded by the peritoneal cavity, but it is covered with visceral peritoneum and is attached to other organs by omenta. Peritoneal Ligaments Peritoneal ligaments are two-layered folds of peritoneum that connect solid viscera to the abdominal walls. The liver, for example, is connected to the diaphragm by the falciform ligament, the coronary ligament, and the right and left triangular ligaments (Figs. 5-8 and 5-10). Omenta Omenta are two-layered folds of peritoneum that connect the stomach to another viscus. The greater omentum connects the greater curvature of the stomach to the transverse colon (Fig. 5-2). It hangs down like an apron in front of the coils of the small intestine and is folded back on itself to be attached to the transverse colon (Fig. 5-6). The lesser omentum suspends the lesser curvature of the stomach from the fissure of the ligamentum venosum and the porta hepatis on the undersurface of the liver (Fig. 5-6). The P.207
gastrosplenic omentum (ligament) connects the stomach to the hilum of the spleen (Fig. 5-5).

Figure 5-5 Transverse sections of the abdomen showing the arrangement of the peritoneum. The arrow in B indicates the position of the opening of the lesser sac. These sections are viewed from below.

Mesenteries Mesenteries are two-layered folds of peritoneum connecting parts of the intestines to the posterior abdominal wall, for example, the mesentery of the small intestine, the transverse mesocolon, and the sigmoid mesocolon (Figs. 5-6 and 5-13). The peritoneal ligaments, omenta, and mesenteries permit blood, lymph vessels, and nerves to reach the viscera. The extent of the peritoneum and the peritoneal cavity should be studied in the transverse and sagittal sections of the abdomen seen in Figures 5-5 and 5-6. Peritoneal Pouches, Recesses, Spaces, and Gutters Lesser Sac The lesser sac lies behind the stomach and the lesser omentum (Figs. 5-5, 5-6, and 5-11). It extends upward as far as the diaphragm and downward between the layers of the greater P.208
omentum. The left margin of the sac is formed by the spleen (Fig. 5-11) and the gastrosplenic omentum and splenicorenal ligament. The right margin opens into the greater sac (the main part of the peritoneal cavity) through the opening of the lesser sac, or epiploic foramen (Fig. 5-7). The opening into the lesser sac (epiploic foramen) has the following boundaries (Fig. 5-7):

Figure 5-6 Sagittal section of the female abdomen showing the arrangement of the peritoneum.
  • Anteriorly: Free border of the lesser omentum, the bile duct, the hepatic artery, and the portal vein (Fig. 5-11)
  • Posteriorly: Inferior vena cava
  • Superiorly: Caudate process of the caudate lobe of the liver
  • Inferiorly: First part of the duodenum

Duodenal Recesses Close to the duodenojejunal junction, there may be four small pocketlike pouches of peritoneum called the superior duodenal, inferior duodenal, paraduodenal, and retroduodenal recesses (Fig. 5-12). Cecal Recesses Folds of peritoneum close to the cecum produce three peritoneal recesses called the superior ileocecal, the inferior ileocecal, and the retrocecal recesses (Fig. 5-13). Intersigmoid Recess The intersigmoid recess is situated at the apex of the inverted, V-shaped root of the sigmoid mesocolon (Fig. 5-13); its mouth opens downward. Subphrenic Spaces The right and left anterior subphrenic spaces lie between the diaphragm and the liver, on each side of the falciform ligament (Fig. 5-14). The right posterior subphrenic space lies between the right lobe of the liver, P.209
the right kidney, and the right colic flexure (Fig. 5-15). The right extraperitoneal space lies between the layers of the coronary ligament and is therefore situated between the liver and the diaphragm (see page 247).

Figure 5-7 Sagittal section through the entrance into the lesser sac showing the important structures that form boundaries to the opening. (Note the arrow passing from the greater sac through the epiploic foramen into the lesser sac.)

Paracolic Gutters The paracolic gutters lie on the lateral and medial sides of the ascending and descending colons, respectively (Figs. 5-5 and 5-14). The subphrenic spaces and the paracolic gutters are clinically important because they may be sites for the collection and movement of infected peritoneal fluid (see page 213). Nerve Supply of the Peritoneum The parietal peritoneum is sensitive to pain, temperature, touch, and pressure. The parietal peritoneum lining the anterior abdominal wall is supplied by the lower six thoracic and first lumbar nerves—that is, the same nerves that innervate the overlying muscles and skin. The central part of the diaphragmatic peritoneum is supplied by the phrenic nerves; peripherally, the diaphragmatic peritoneum is supplied by the lower six thoracic nerves. The parietal peritoneum in the pelvis is mainly supplied by the obturator nerve, a branch of the lumbar plexus. The visceral peritoneum is sensitive only to stretch and tearing and is not sensitive to touch, pressure, or temperature. It is supplied by autonomic afferent nerves that supply the viscera or are traveling in the mesenteries. Overdistention of a viscus leads to the sensation of pain. The mesenteries of the small and large intestines are sensitive to mechanical stretching. Functions of the Peritoneum The peritoneal fluid, which is pale yellow and somewhat viscid, contains leukocytes. It is secreted by the peritoneum and ensures that the mobile viscera glide easily on one another. As a result of the movements of the diaphragm and the abdominal muscles, together with the peristaltic movements of the intestinal tract, the peritoneal fluid is not static. Experimental evidence has shown that particulate matter introduced into the lower part of the peritoneal cavity reaches the subphrenic peritoneal spaces rapidly, whatever the position of the body. It seems that intraperitoneal movement of fluid toward the diaphragm is continuous (Fig. 5-14), and there it is quickly absorbed into the subperitoneal lymphatic capillaries. This can be explained on the basis that the area of peritoneum is extensive in the region of the diaphragm and the respiratory movements of the diaphragm aid lymph flow in the lymph vessels. The peritoneal coverings of the intestine tend to stick together in the presence of infection. The greater omentum, which is kept constantly on the move by the peristalsis of the neighboring intestinal tract, may adhere to other peritoneal surfaces around a focus of infection. In this manner, many of the intraperitoneal infections are sealed off and remain localized. The peritoneal folds play an important part in suspending the various organs within the peritoneal cavity and serve as a means of conveying the blood vessels, lymphatics, and nerves to these organs. Large amounts of fat are stored in the peritoneal ligaments and mesenteries, and especially large amounts can be found in the greater omentum. P.210

Figure 5-8 Liver as seen from in front (A), from above (B), and from behind (C). Note the position of the peritoneal reflections, the bare areas, and the peritoneal ligaments
Figure 5-9 A plastinized specimen of the liver as seen on its posteroinferior (visceral) surface. The portal vein has been transfused with white plastic and the inferior vena cava with dark blue plastic. Outside the liver, the distended biliary ducts and gallbladder have been injected with yellow plastic and the hepatic artery with red plastic. The liver was then immersed in corrosive fluid to remove the liver tissue. Note the profuse branching of the portal vein as its white terminal branches enter the portal canals between the liver lobules; the dark blue tributaries of many of the hepatic veins can also be seen.

P.211

Figure 5-10 Attachment of the lesser omentum to the stomach and the posterior surface of the liver.
Figure 5-11 Transverse section of the lesser sac showing the arrangement of the peritoneum in the formation of the lesser omentum, the gastrosplenic omentum, and the splenicorenal ligament. Arrow indicates the position of the opening of the lesser sac.

P.212

Figure 5-12 Peritoneal recesses, which may be present in the region of the duodenojejunal junction. Note the presence of the inferior mesenteric vein in the peritoneal fold, forming the paraduodenal recess.
Figure 5-13 Peritoneal recesses (arrows) in the region of the cecum and the recess related to the sigmoid mesocolon.

P.213

Figure 5-14 Normal direction of flow of the peritoneal fluid from different parts of the peritoneal cavity to the subphrenic spaces.

Clinical Notes The Peritoneum and Peritoneal Cavity Movement of Peritoneal Fluid The peritoneal cavity is divided into an upper part within the abdomen and a lower part in the pelvis. The abdominal part is further subdivided by the many peritoneal reflections into important recesses and spaces, which, in turn, are continued into the paracolic gutters (Fig. 5-15). The attachment of the transverse mesocolon and the mesentery of the small intestine to the posterior abdominal wall provides natural peritoneal barriers that may hinder the movement of infected peritoneal fluid from the upper part to the lower part of the peritoneal cavity. It is interesting to note that when the patient is in the supine position the right subphrenic peritoneal space and the pelvic cavity are the lowest areas of the peritoneal cavity and the region of the pelvic brim is the highest area (Fig. 5-15). Peritoneal Infection Infection may gain entrance to the peritoneal cavity through several routes: from the interior of the gastrointestinal tract and gallbladder, through the anterior abdominal wall, via the uterine tubes in females (gonococcal peritonitis in adults and pneumococcal peritonitis in children occur through this route), and from the blood. Collection of infected peritoneal fluid in one of the subphrenic spaces is often accompanied by infection of the pleural cavity. It is common to find a localized empyema in a patient with a subphrenic abscess. It is believed that the infection spreads from the peritoneum to the pleura via the diaphragmatic lymph vessels. A patient with a subphrenic abscess may complain of pain over the shoulder. (This also holds true for collections of blood under the diaphragm, which irritate the parietal diaphragmatic peritoneum.) The skin of the shoulder is supplied by the supraclavicular nerves (C3 and 4), which have the same segmental origin as the phrenic nerve, which supplies the peritoneum in the center of the undersurface of the diaphragm. To avoid the accumulation of infected fluid in the subphrenic spaces and to delay the absorption of toxins from intraperitoneal infections, it is common nursing practice to sit a patient up in bed with the back at an angle of 45°. In this position, the infected peritoneal fluid tends to gravitate downward into the pelvic cavity, where the rate of toxin absorption is slow (Fig. 5-15). Greater Omentum Localization of Infection The greater omentum is often referred to by the surgeons as the abdominal policeman. The lower and the right and left margins are free, and it moves about the peritoneal cavity in response to the peristaltic movements of the neighboring gut. In the first 2 years of life it is poorly developed and thus is less protective in a young child. Later, however, in an acutely inflamed appendix, for example, the inflammatory exudate causes the omentum to adhere to the appendix and wrap itself around the infected organ (Fig. 5-16). By this means, the infection is often localized to a small area of the peritoneal cavity, thus saving the patient from a serious diffuse peritonitis.

Figure 5-15 Direction of flow of the peritoneal fluid. 1. Normal flow upward to the subphrenic spaces. 2. Flow of inflammatory exudate in peritonitis. 3. The two sites where inflammatory exudate tends to collect when the patient is nursed in the supine position. 4. Accumulation of inflammatory exudate in the pelvis when the patient is nursed in the inclined position.
Figure 5-16 A. The normal greater omentum. B. The greater omentum wrapped around an inflamed appendix. C. The greater omentum adherent to the base of a gastric ulcer. One important function of the greater omentum is to attempt to limit the spread of intraperitoneal infections.

Greater Omentum as a Hernial Plug The greater omentum has been found to plug the neck of a hernial sac and prevent the entrance of coils of small intestine. Greater Omentum in Surgery Surgeons sometimes use the omentum to buttress an intestinal anastomosis or in the closure of a perforated gastric or duodenal ulcer. Torsion of the Greater Omentum The greater omentum may undergo torsion, and if extensive, the blood supply to a part of it may be cut off, causing necrosis. Ascites Ascites is essentially an excessive accumulation of peritoneal fluid within the peritoneal cavity. Ascites can occur secondary to hepatic cirrhosis (portal venous congestion), malignant disease (e.g., cancer of the ovary), or congestive heart failure (systemic venous congestion). In a thin patient, as much as 1500 mL has to accumulate before ascites can be recognized clinically. In obese individuals, a far greater amount has to collect before it can be detected. The withdrawal of peritoneal fluid from the peritoneal cavity is described on page 188. Peritoneal Pain From the Parietal Peritoneum The parietal peritoneum lining the anterior abdominal wall is supplied by the lower six thoracic nerves and the first lumbar nerve. Abdominal pain originating from the parietal peritoneum is therefore of the somatic type and can be precisely localized; it is usually severe (see Abdominal Pain, page 281). An inflamed parietal peritoneum is extremely sensitive to stretching. This fact is made use of clinically in diagnosing peritonitis. Pressure is applied to the abdominal wall with a single finger over the site of the inflammation. The pressure is then removed by suddenly withdrawing the finger. The abdominal wall rebounds, resulting in extreme local pain, which is known as rebound tenderness. It should always be remembered that the parietal peritoneum in the pelvis is innervated by the obturator nerve and can be palpated by means of a rectal or vaginal examination. An inflamed appendix may hang down into the pelvis and irritate the parietal peritoneum. A pelvic examination can detect extreme tenderness of the parietal peritoneum on the right side (see page 345). From the Visceral Peritoneum The visceral peritoneum, including the mesenteries, is innervated by autonomic afferent nerves. Stretch caused by overdistension of a viscus or pulling on a mesentery gives rise to the sensation of pain. The sites of origin of visceral pain are shown in Figure 5-17. Because the gastrointestinal tract arises embryologically as a midline structure and receives a bilateral nerve supply, pain is referred to the midline. Pain arising from an abdominal viscus is dull and poorly localized (see Abdominal Pain, page 281). Peritoneal Dialysis Because the peritoneum is a semipermeable membrane, it allows rapid bidirectional transfer of substances across itself. Because the surface area of the peritoneum is enormous, this transfer property has been made use of in patients with acute renal insufficiency. The efficiency of this method is only a fraction of that achieved by hemodialysis. A watery solution, the dialysate, is introduced through a catheter through a small midline incision through the anterior abdominal wall below the umbilicus. The technique is the same as peritoneal lavage (see page 189). The products of metabolism, such as urea, diffuse through the peritoneal lining cells from the blood vessels into the dialysate and are removed from the patient. Internal Abdominal Hernia Occasionally, a loop of intestine enters a peritoneal pouch or recess (e.g., the lesser sac or the duodenal recesses) and becomes strangulated at the edges of the recess. Remember that important structures form the boundaries of the entrance into the lesser sac and that the inferior mesenteric vein often lies in the anterior wall of the paraduodenal recess.

Figure 5-17 Some important skin areas involved in referred visceral pain.

P.214
P.215
P.216
Embryologic Notes Development of the Peritoneum and the Peritoneal Cavity Once the lateral mesoderm has split into somatic and splanchnic layers, a cavity is formed between the two, called the intraembryonic coelom. The peritoneal cavity is derived from that part of the embryonic coelom situated caudal to the septum transversum. In the earliest stages, the peritoneal cavity is in free communication with the extraembryonic coelom on each side (see Fig. 4-36B). Later, with the development of the head, tail, and lateral folds of the embryo, this wide area of communication becomes restricted to the small area within the umbilical cord. Early in development, the peritoneal cavity is divided into right and left halves by a central partition formed by the dorsal mesentery, the gut, and the small ventral mesentery (Fig. 5-18). However, the ventral mesentery extends only for a short distance along the gut (see below), so that below this level the right and left halves of the peritoneal cavity are in free communication (Fig. 5-18). As a result of the enormous growth of the liver and the enlargement of the developing kidneys, the capacity of the abdominal cavity becomes greatly reduced at about the sixth week of development. It is at this time that the small remaining communication between the peritoneal cavity and extraembryonic coelom becomes important. An intestinal loop is forced out of the abdominal cavity through the umbilicus into the umbilical cord. This physiologic herniation of the midgut takes place during the sixth week of development. Formation of the Peritoneal Ligaments and Mesenteries The peritoneal ligaments are developed from the ventral and dorsal mesenteries. The ventral mesentery is formed from the mesoderm of the septum transversum (derived from the cervical somites, which migrate downward). The ventral mesentery forms the falciform ligament, the lesser omentum, and the coronary and triangular ligaments of the liver (Fig. 5-18). The dorsal mesentery is formed from the fusion of the splanchnopleuric mesoderm on the two sides of the embryo. It extends from the posterior abdominal wall to the posterior border of the abdominal part of the gut (Figs. 4-36 and 5-18). The dorsal mesentery forms the gastrophrenic ligament, the gastrosplenic omentum, the splenicorenal ligament, the greater omentum, and the mesenteries of the small and large intestines. Formation of the Lesser and Greater Peritoneal Sacs The extensive growth of the right lobe of the liver pulls the ventral mesentery to the right and causes rotation of the stomach and duodenum (Fig. 5-19). By this means, the upper right part of the peritoneal cavity becomes incorporated into the lesser sac. The right free border of the ventral mesentery becomes the right border of the lesser omentum and the anterior boundary of the entrance into the lesser sac. The remaining part of the peritoneal cavity, which is not included in the lesser sac, is called the greater sac, and the two sacs are in communication through the epiploic foramen. Formation of the Greater Omentum The spleen is developed in the upper part of the dorsal mesentery, and the greater omentum is formed as a result of the rapid and extensive growth of the dorsal mesentery caudal to the spleen. To begin with, the greater omentum extends from the greater curvature of the stomach to the posterior abdominal wall superior to the transverse mesocolon. With continued growth, it reaches inferiorly as an apronlike double layer of peritoneum anterior to the transverse colon. Later, the posterior layer of the omentum fuses with the transverse mesocolon; as a result, the greater omentum becomes attached to the anterior surface of the transverse colon (Fig. 5-19). As development proceeds, the omentum becomes laden with fat. The inferior recess of the lesser sac extends inferiorly between the anterior and the posterior layers of the fold of the greater omentum.

Figure 5-18 Ventral and dorsal mesenteries and the organs that develop within them.
Figure 5-19 The rotation of the stomach and the formation of the greater omentum and lesser sac.

P.217
Gastrointestinal Tract Esophagus (Abdominal Portion) The esophagus is a muscular, collapsible tube about 10 in. (25 cm) long that joins the pharynx to the stomach. The greater part of the esophagus lies within the thorax (see page 127). The esophagus enters the abdomen through an opening in the right crus of the diaphragm (Fig. 5-4). After a course of about 0.5 in. (1.25 cm), it enters the stomach on its right side. Relations The esophagus is related anteriorly to the posterior surface of the left lobe of the liver and posteriorly to the left crus of the diaphragm. The left and right vagi lie on its anterior and posterior surfaces, respectively. Blood Supply Arteries The arteries are branches from the left gastric artery (Fig. 5-20). Veins The veins drain into the left gastric vein, a tributary of the portal vein (see portal–systemic anastomosis, page 246). Lymph Drainage The lymph vessels follow the arteries into the left gastric nodes. Nerve Supply The nerve supply is the anterior and posterior gastric nerves (vagi) and sympathetic branches of the thoracic part of the sympathetic trunk. Function The esophagus conducts food from the pharynx into the stomach. Wavelike contractions of the muscular coat, called peristalsis, propel the food onward. Gastroesophageal Sphincter No anatomic sphincter exists at the lower end of the esophagus. However, the circular layer of smooth muscle in this region serves as a physiologic sphincter. As the food descends through the esophagus, relaxation of the muscle at the lower end occurs ahead of the peristaltic wave so that the food enters the stomach. The tonic contraction of this sphincter prevents the stomach contents from regurgitating into the esophagus. The closure of the sphincter is under vagal control, and this can be augmented by the hormone gastrin and reduced in response to secretin, cholecystokinin, and glucagon. P.218

Figure 5-20 Arteries that supply the stomach. Note that all the arteries are derived from branches of the celiac artery.

Clinical Notes The Esophagus Narrow Areas of the Esophageal Lumen The esophagus is narrowed at three sites: at the beginning, behind the cricoid cartilage of the larynx; where the left bronchus and the arch of the aorta cross the front of the esophagus; and where the esophagus enters the stomach. These three sites may offer resistance to the passage of a tube down the esophagus into the stomach (see Fig. 3-44). Achalasia of the Cardia (Esophagogastric Junction) The cause of achalasia is unknown, but it is associated with a degeneration of the parasympathetic plexus (Auerbach’s plexus) in the wall of the esophagus. The primary site of the disorder may be in the innervation of the cardioesophageal sphincter by the vagus nerves. Dysphagia (difficulty in swallowing) and regurgitation are common symptoms that are later accompanied by proximal dilatation and distal narrowing of the esophagus. Bleeding Esophageal Varices At the lower third of the esophagus is an important portal–systemic venous anastomosis (see page 246). Here, the esophageal tributaries of the left gastric vein (which drains into the portal vein) anastomose with the esophageal tributaries of the azygos veins (systemic veins). Should the portal vein become obstructed, as, for example, in cirrhosis of the liver, portal hypertension develops, resulting in dilatation and varicosity of the portal–systemic anastomoses. Varicosed esophageal veins may rupture, causing severe vomiting of blood (hematemesis). Anatomy of the Insertion of the Sengstaken-Blakemore Balloon for Esophageal Hemorrhage The Sengstaken-Blakemore balloon is used for the control of massive esophageal hemorrhage from esophageal varices. A gastric balloon anchors the tube against the esophageal–gastric junction. An esophageal balloon occludes the esophageal varices by counterpressure. The tube is inserted through the nose or by using the oral route. The lubricated tube is passed down into the stomach, and the gastric balloon is inflated. In the average adult the distance between the external orifices of the nose and the stomach is 17.2 in. (44 cm), and the distance between the incisor teeth and the stomach is 16 in. (41 cm). Anatomy of the Complications

  • Difficulty in passing the tube through the nose
  • Damage to the esophagus from overinflation of the esophageal tube
  • Pressure on neighboring mediastinal structures as the esophagus is expanded by the balloon within its lumen
  • Persistent hiccups caused by irritation of the diaphragm by the distended esophagus and irritation of the stomach by the blood

P.219
Stomach Location and Description The stomach is the dilated portion of the alimentary canal and has three main functions: It stores food (in the adult it has a capacity of about 1500 mL), it mixes the food with gastric secretions to form a semifluid chyme, and it controls the rate of delivery of the chyme to the small intestine so that efficient digestion and absorption can take place. The stomach is situated in the upper part of the abdomen, extending from beneath the left costal margin region into the epigastric and umbilical regions. Much of the stomach lies under cover of the lower ribs. It is roughly J-shaped and has two openings, the cardiac and pyloric orifices; two curvatures, the greater and lesser curvatures; and two surfaces, an anterior and a posterior surface (Fig. 5-21).

Figure 5-21 Stomach showing the parts, muscular coats, and mucosal lining. Note the increased thickness of the circular muscle forming the pyloric sphincter.

The stomach is relatively fixed at both ends but is very mobile in between. It tends to be high and transversely arranged in the short, obese person (steer-horn stomach) and elongated vertically in the tall, thin person (J-shaped stomach). Its shape undergoes considerable variation in the same person and depends on the volume of its contents, the position of the body, and the phase of respiration. The stomach is divided into the following parts (Fig. 5-21):

  • Fundus: This is dome-shaped and projects upward and to the left of the cardiac orifice. It is usually full of gas.
  • Body: This extends from the level of the cardiac orifice to the level of the incisura angularis, a constant notch in the lower part of the lesser curvature (Fig. 5-21).
  • Pyloric antrum: This extends from the incisura angularis to the pylorus (Fig. 5-21).
  • P.220

  • Pylorus: This is the most tubular part of the stomach. The thick muscular wall is called the pyloric sphincter, and the cavity of the pylorus is the pyloric canal (Fig. 5-21).

The lesser curvature forms the right border of the stomach and extends from the cardiac orifice to the pylorus (Fig. 5-21). It is suspended from the liver by the lesser omentum. The greater curvature is much longer than the lesser curvature and extends from the left of the cardiac orifice, over the dome of the fundus, and along the left border of the stomach to the pylorus (Fig. 5-21). The gastrosplenic omentum (ligament) extends from the upper part of the greater curvature to the spleen, and the greater omentum extends from the lower part of the greater curvature to the transverse colon (Fig. 5-11). The cardiac orifice is where the esophagus enters the stomach (Fig. 5-21). Although no anatomic sphincter can be demonstrated here, a physiologic mechanism exists that prevents regurgitation of stomach contents into the esophagus (see page 217). The pyloric orifice is formed by the pyloric canal, which is about 1 in. (2.5 cm) long. The circular muscle coat of the stomach is much thicker here and forms the anatomic and physiologic pyloric sphincter (Fig. 5-21). The pylorus lies on the transpyloric plane, and its position can be recognized by a slight constriction on the surface of the stomach. Function of the Pyloric Sphincter The pyloric sphincter controls the outflow of gastric contents into the duodenum. The sphincter receives motor fibers from the sympathetic system and inhibitory fibers from the vagi. In addition, the pylorus is controlled by local nervous and hormonal influences from the stomach and duodenal walls. For example, the stretching of the stomach due to filling will stimulate the myenteric nerve plexus in its wall and reflexly cause relaxation of the sphincter. The mucous membrane of the stomach is thick and vascular and is thrown into numerous folds, or rugae, that are mainly longitudinal in direction (Fig. 5-21). The folds flatten out when the stomach is distended. The muscular wall of the stomach contains longitudinal fibers, circular fibers, and oblique fibers (Fig. 5-21). The peritoneum (visceral peritoneum) completely surrounds the stomach. It leaves the lesser curvature as the lesser omentum and the greater curvature as the gastrosplenic omentum and the greater omentum. Relations

  • Anteriorly: The anterior abdominal wall, the left costal margin, the left pleura and lung, the diaphragm, and the left lobe of the liver (Figs. 5-2 and 5-6)
  • Posteriorly: The lesser sac, the diaphragm, the spleen, the left suprarenal gland, the upper part of the left kidney, the splenic artery, the pancreas, the transverse mesocolon, and the transverse colon (Figs. 5-4, 5-6, and 5-11)

Blood Supply Arteries The arteries are derived from the branches of the celiac artery (Fig. 5-20). The left gastric artery arises from the celiac artery. It passes upward and to the left to reach the esophagus and then descends along the lesser curvature of the stomach. It supplies the lower third of the esophagus and the upper right part of the stomach. The right gastric artery arises from the hepatic artery at the upper border of the pylorus and runs to the left along the lesser curvature. It supplies the lower right part of the stomach. The short gastric arteries arise from the splenic artery at the hilum of the spleen and pass forward in the gastrosplenic omentum (ligament) to supply the fundus. The left gastroepiploic artery arises from the splenic artery at the hilum of the spleen and passes forward in the gastrosplenic omentum (ligament) to supply the stomach along the upper part of the greater curvature. The right gastroepiploic artery arises from the gastroduodenal branch of the hepatic artery. It passes to the left and supplies the stomach along the lower part of the greater curvature. Veins The veins drain into the portal circulation (Fig. 5-22). The left and right gastric veins drain directly into the portal vein. The short gastric veins and the left gastroepiploic veins join the splenic vein. The right gastroepiploic vein joins the superior mesenteric vein. Lymph Drainage The lymph vessels (Fig. 5-23) follow the arteries into the left and right gastric nodes, the left and right gastroepiploic nodes, and the short gastric nodes. All lymph from the stomach eventually passes to the celiac nodes located around the root of the celiac artery on the posterior abdominal wall. Nerve Supply The nerve supply includes sympathetic fibers derived from the celiac plexus and parasympathetic fibers from the right and left vagus nerves (Fig. 5-24). The anterior vagal trunk, which is formed in the thorax mainly from the left vagus nerve, enters the abdomen on the anterior surface of the esophagus. The trunk, which may be single or multiple, then divides into branches that supply the anterior surface of the stomach. A large hepatic branch passes up to the liver, and from this a pyloric branch passes down to the pylorus (Fig. 5-24). The posterior vagal trunk, which is formed in the thorax mainly from the right vagus nerve, enters the abdomen on the posterior surface of the esophagus. The trunk then divides into branches that supply mainly the posterior surface of the stomach. A large branch passes to the celiac and superior mesenteric plexuses and is distributed to the intestine as far as the splenic flexure and to the pancreas (Fig. 5-24). The sympathetic innervation of the stomach carries a proportion of pain-transmitting nerve fibers, whereas the parasympathetic vagal fibers are secretomotor to the gastric glands and motor to the muscular wall of the stomach. The pyloric sphincter receives motor fibers from the sympathetic system and inhibitory fibers from the vagi. P.221

Figure 5-22 Tributaries of the portal vein.

P.222

Figure 5-23 Lymph drainage of the stomach. Note that all the lymph eventually passes through the celiac lymph nodes.
Figure 5-24 Distribution of the anterior and posterior vagal trunks within the abdomen. Note that the celiac branch of the posterior vagal trunk is distributed with the sympathetic nerves as far down the intestinal tract as the left colic flexure.

P.223
Clinical Notes Trauma to the Stomach Apart from its attachment to the esophagus at the cardiac orifice and its continuity with the duodenum at the pylorus, the stomach is relatively mobile. It is protected on the left by the lower part of the rib cage. These factors greatly protect the stomach from blunt trauma to the abdomen. However, its large size makes it vulnerable to gunshot wounds. Gastric Ulcer The mucous membrane of the body of the stomach and, to a lesser extent, that of the fundus produce acid and pepsin. The secretion of the antrum and pyloric canal is mucous and weakly alkaline (Fig. 5-25). The secretion of acid and pepsin is controlled by two mechanisms: nervous and hormonal. The vagus nerves are responsible for the nervous control, and the hormone gastrin, produced by the antral mucosa, is responsible for the hormonal control. In the surgical treatment of chronic gastric and duodenal ulcers, attempts are made to reduce the amount of acid secretion by sectioning the vagus nerves (vagotomy) and by removing the gastrin-bearing area of mucosa, the antrum (partial gastrectomy). Gastric ulcers occur in the alkaline-producing mucosa of the stomach, usually on or close to the lesser curvature. A chronic ulcer invades the muscular coats and, in time, involves the peritoneum so that the stomach adheres to neighboring structures. An ulcer situated on the posterior wall of the stomach may perforate into the lesser sac or become adherent to the pancreas. Erosion of the pancreas produces pain referred to the back. The splenic artery runs along the upper border of the pancreas, and erosion of this artery may produce fatal hemorrhage. A penetrating ulcer of the anterior stomach wall may result in the escape of stomach contents into the greater sac, producing diffuse peritonitis. The anterior stomach wall may, however, adhere to the liver, and the chronic ulcer may penetrate the liver substance. Gastric Pain The sensation of pain in the stomach is caused by the stretching or spasmodic contraction of the smooth muscle in its walls and is referred to the epigastrium. It is believed that the pain-transmitting fibers leave the stomach in company with the sympathetic nerves. They pass through the celiac ganglia and reach the spinal cord via the greater splanchnic nerves. Cancer of the Stomach Because the lymphatic vessels of the mucous membrane and submucosa of the stomach are in continuity, it is possible for cancer cells to travel to different parts of the stomach, some distance away from the primary site. Cancer cells also often pass through or bypass the local lymph nodes and are held up in the regional nodes. For these reasons, malignant disease of the stomach is treated by total gastrectomy, which includes the removal of the lower end of the esophagus and the first part of the duodenum; the spleen and the gastrosplenic and splenicorenal ligaments and their associated lymph nodes; the splenic vessels; the tail and body of the pancreas and their associated nodes; the nodes along the lesser curvature of the stomach; and the nodes along the greater curvature, along with the greater omentum. This radical operation is a desperate attempt to remove the stomach en bloc and, with it, its lymphatic field. The continuity of the gut is restored by anastomosing the esophagus with the jejunum. Gastroscopy Gastroscopy is the viewing of the mucous membrane of the stomach through an illuminated tube fitted with a lens system. The patient is anesthetized and the gastroscope is passed into the stomach, which is then inflated with air. With a flexible fiberoptic instrument, direct visualization of different parts of the gastric mucous membrane is possible. It is also possible to perform a mucosal biopsy through a gastroscope. Nasogastric Intubation Nasogastric intubation is a common procedure and is performed to empty the stomach, to decompress the stomach in cases of intestinal obstruction, or before operations on the gastrointestinal tract; it may also be performed to obtain a sample of gastric juice for biochemical analysis.

  • The patient is placed in the semiupright position or left lateral position to avoid aspiration.
  • The well-lubricated tube is inserted through the wider nostril and is directed backward along the nasal floor.
  • Once the tube has passed the soft palate and entered the oral pharynx, decreased resistance is felt, and the conscious patient will feel like gagging.
  • Some important distances in the adult may be useful. From the nostril (external nares) to the cardiac orifice of the stomach is about 17.2 in. (44 cm), and from the cardiac orifice to the pylorus of the stomach is 4.8 to 5.6 in. (12 to 14 cm). The curved course taken by the tube from the cardiac orifice to the pylorus is usually longer, 6.0 to 10.0 in. (15 to 25 cm) (see Fig. 3-51).

Anatomic Structures That May Impede the Passage of the Nasogastric Tube

  • A deviated nasal septum makes the passage of the tube difficult on the narrower side.
  • Three sites of esophageal narrowing may offer resistance to the nasogastric tube—at the beginning of the esophagus behind the cricoid cartilage (7.2 in. [18 cm]), where the left bronchus and the arch of the aorta cross the front of the esophagus (11.2 in. [28 cm]), and where the esophagus enters the stomach (17.2 in. [44 cm]). The upper esophageal narrowing may be overcome by gently grasping the wings of the thyroid cartilage and pulling the larynx forward. This maneuver opens the normally collapsed esophagus and permits the tube to pass down without further delay.

Anatomy of Complications

  • The nasogastric tube enters the larynx instead of the esophagus.
  • Rough insertion of the tube into the nose will cause nasal bleeding from the mucous membrane.
  • Penetration of the wall of the esophagus or stomach. Always aspirate tube for gastric contents to confirm successful entrance into the stomach.

P.224

Figure 5-25 Areas of the stomach that produce acid and pepsin (blue) and alkali and gastrin (red).

Small Intestine The small intestine is the longest part of the alimentary canal and extends from the pylorus of the stomach to the ileocecal junction (Fig. 5-1). The greater part of digestion and food absorption takes place in the small intestine. It is divided into three parts: the duodenum, the jejunum, and the ileum. Duodenum Location and Description The duodenum is a C-shaped tube, about 10 in. (25 cm) long, which joins the stomach to the jejunum. It receives the openings of the bile and pancreatic ducts. The duodenum curves around the head of the pancreas (Fig. 5-26). The first inch (2.5 cm) of the duodenum resembles the stomach in that it is covered on its anterior and posterior surfaces with peritoneum and has the lesser omentum attached to its upper border and the greater omentum attached to its lower border; the lesser sac lies behind this short segment. The remainder of the duodenum is retroperitoneal, being only partially covered by peritoneum.

Figure 5-26 Pancreas and anterior relations of the kidneys.

Parts of the Duodenum The duodenum is situated in the epigastric and umbilical regions and, for purposes of description, is divided into four parts. First Part of the Duodenum The first part of the duodenum begins at the pylorus and runs upward and backward on the transpyloric plane at the level of the first lumbar vertebra (Figs. 5-26 and 5-27). The relations of this part are as follows:

  • Anteriorly: The quadrate lobe of the liver and the gallbladder (Fig. 5-10)
  • Posteriorly: The lesser sac (first inch only), the gastroduodenal artery, the bile duct and portal vein, and the inferior vena cava (Fig. 5-27)
  • Superiorly: The entrance into the lesser sac (the epiploic foramen) (Figs. 5-7 and 5-11)
  • Inferiorly: The head of the pancreas (Fig. 5-26)

Second Part of the Duodenum The second part of the duodenum runs vertically downward in front of the hilum of the right kidney on the right side of the second and third lumbar vertebrae (Figs. 5-26 and 5-27). About halfway down its medial border, the bile duct and the main pancreatic duct pierce the duodenal wall. They unite to form the ampulla that opens on the summit of the major duodenal P.225
papilla (Fig. 5-28). The accessory pancreatic duct, if present, opens into the duodenum a little higher up on the minor duodenal papilla (Figs. 5-27 and 5-28).

Figure 5-27 Posterior relations of the duodenum and the pancreas. The numbers represent the four parts of the duodenum.

The relations of this part are as follows:

  • Anteriorly: The fundus of the gallbladder and the right lobe of the liver, the transverse colon, and the coils of the small intestine (Fig. 5-29)
  • Posteriorly: The hilum of the right kidney and the right ureter (Fig. 5-27)
  • Laterally: The ascending colon, the right colic flexure, and the right lobe of the liver (Fig. 5-27)
  • Medially: The head of the pancreas, the bile duct, and the main pancreatic duct (Figs. 5-27 and 5-28)
Figure 5-28 Entrance of the bile duct and the main and accessory pancreatic ducts into the second part of the duodenum. Note the smooth lining of the first part of the duodenum, the plicae circulares of the second part, and the major duodenal papilla.

Third Part of the Duodenum The third part of the duodenum runs horizontally to the left on the subcostal plane, passing in front of the vertebral column and following the lower margin of the head of the pancreas (Figs. 5-26 and 5-27). The relations of this part are as follows:

  • Anteriorly: The root of the mesentery of the small intestine, the superior mesenteric vessels contained within it, and coils of jejunum (Figs. 5-26 and 5-27)
  • Posteriorly: The right ureter, the right psoas muscle, the inferior vena cava, and the aorta (Fig. 5-27)
  • Superiorly: The head of the pancreas (Fig. 5-26)
  • Inferiorly: Coils of jejunum

P.226

Figure 5-29 The bile ducts and the gallbladder. Note the relation of the gallbladder to the transverse colon and the duodenum.
Figure 5-30 Attachment of the root of the mesentery of the small intestine to the posterior abdominal wall. Note that it extends from the duodenojejunal flexure on left of the aorta, downward and to the right to the ileocecal junction. The superior mesenteric artery lies in the root of the mesentery.

P.227
Fourth Part of the Duodenum The fourth part of the duodenum runs upward and to the left to the duodenojejunal flexure (Figs. 5-26 and 5-27). The flexure is held in position by a peritoneal fold, the ligament of Treitz, which is attached to the right crus of the diaphragm (Fig. 5-12). The relations of this part are as follows:

  • Anteriorly: The beginning of the root of the mesentery and coils of jejunum (Fig. 5-30)
  • Posteriorly: The left margin of the aorta and the medial border of the left psoas muscle (Fig. 5-27)

Mucous Membrane and Duodenal Papillae The mucous membrane of the duodenum is thick. In the first part of the duodenum it is smooth (Fig. 5-28). In the remainder of the duodenum it is thrown into numerous circular folds called the plicae circulares. At the site where the bile duct and the main pancreatic duct pierce the medial wall of the second part is a small, rounded elevation called the major duodenal papilla (Fig. 5-28). The accessory pancreatic duct, if present, opens into the duodenum on a smaller papilla about 0.75 in. (1.9 cm) above the major duodenal papilla. Blood Supply Arteries The upper half is supplied by the superior pancreaticoduodenal artery, a branch of the gastroduodenal artery (Figs. 5-20 and 5-26). The lower half is supplied by the inferior pancreaticoduodenal artery, a branch of the superior mesenteric artery. Veins The superior pancreaticoduodenal vein drains into the portal vein; the inferior vein joins the superior mesenteric vein (Fig. 5-22). Lymph Drainage The lymph vessels follow the arteries and drain upward via pancreaticoduodenal nodes to the gastroduodenal nodes and then to the celiac nodes and downward via pancreaticoduodenal nodes to the superior mesenteric nodes around the origin of the superior mesenteric artery. Nerve Supply The nerves are derived from sympathetic and parasympathetic (vagus) nerves from the celiac and superior mesenteric plexuses. Clinical Notes Trauma to the Duodenum Apart from the first inch, the duodenum is rigidly fixed to the posterior abdominal wall by peritoneum and therefore cannot move away from crush injuries. In severe crush injuries to the anterior abdominal wall, the third part of the duodenum may be severely crushed or torn against the third lumbar vertebra. Duodenal Ulcer As the stomach empties its contents into the duodenum, the acid chyme is squirted against the anterolateral wall of the first part of the duodenum. This is thought to be an important factor in the production of a duodenal ulcer at this site. An ulcer of the anterior wall of the first inch of the duodenum may perforate into the upper part of the greater sac, above the transverse colon. The transverse colon directs the escaping fluid into the right lateral paracolic gutter and thus down to the right iliac fossa. The differential diagnosis between a perforated duodenal ulcer and a perforated appendix may be difficult. An ulcer of the posterior wall of the first part of the duodenum may penetrate the wall and erode the relatively large gastroduodenal artery, causing a severe hemorrhage. The gastroduodenal artery is a branch of the hepatic artery, a branch of the celiac trunk (Fig. 5-4). Duodenal Recesses The importance of the duodenal recesses and the occurrence of herniae of the intestine were already alluded to on page 208. Important Duodenal Relations The relation to the duodenum of the gallbladder, the transverse colon, and the right kidney should be remembered. Cases have been reported in which a large gallstone ulcerated through the gallbladder wall into the duodenum. Operations on the colon and right kidney have resulted in damage to the duodenum. Jejunum and Ileum Location and Description The jejunum and ileum measure about 20 ft (6 m) long; the upper two fifths of this length make up the jejunum. Each has distinctive features, but there is a gradual change from one to the other. The jejunum begins at the duodenojejunal flexure, and the ileum ends at the ileocecal junction. The coils of jejunum and ileum re freely mobile and are attached to the posterior abdominal wall by a fan-shaped fold of peritoneum known as the mesentery of the small intestine (Fig. 5-30). The long free edge of the fold encloses the mobile intestine. The short root of the fold is continuous with the parietal peritoneum on the posterior abdominal wall along a line that extends downward and to the right from the left side of the second lumbar vertebra to the region of the right sacroiliac joint. The root of the mesentery permits the entrance and exit of the branches of the superior mesenteric artery and vein, lymph vessels, and nerves into the space between the two layers of peritoneum forming the mesentery. In the living, the jejunum can be distinguished from the ileum by the following features:

  • The jejunum lies coiled in the upper part of the peritoneal cavity below the left side of the transverse mesocolon; the ileum is in the lower part of the cavity and in the pelvis (Fig. 5-3).
  • The jejunum is wider bored, thicker walled, and redder than the ileum. The jejunal wall feels thicker because the permanent infoldings of the mucous membrane, the plicae circulares, are larger, more numerous, and closely set in the jejunum, whereas in the upper part of the ileum P.228
    they are smaller and more widely separated and in the lower part they are absent (Fig. 5-31).
    Figure 5-31 Some external and internal differences between the jejunum and the ileum.
  • The jejunal mesentery is attached to the posterior abdominal wall above and to the left of the aorta, whereas the ileal mesentery is attached below and to the right of the aorta.
  • The jejunal mesenteric vessels form only one or two arcades, with long and infrequent branches passing to the intestinal wall. The ileum receives numerous short terminal vessels that arise from a series of three or four or even more arcades (Fig. 5-31).
  • At the jejunal end of the mesentery, the fat is deposited near the root and is scanty near the intestinal wall. At the ileal end of the mesentery the fat is deposited throughout so that it extends from the root to the intestinal wall (Fig. 5-31).
  • Aggregations of lymphoid tissue (Peyer’s patches) are present in the mucous membrane of the lower ileum along the antimesenteric border (Fig. 5-31). In the living these may be visible through the wall of the ileum from the outside.

Blood Supply Arteries The arterial supply is from branches of the superior mesenteric artery (Fig. 5-32). The intestinal branches arise from the left side of the artery and run in the mesentery to reach the gut. They anastomose with one another to form a series of arcades. The lowest part of the ileum is also supplied by the ileocolic artery. Veins The veins correspond to the branches of the superior mesenteric artery and drain into the superior mesenteric vein (Fig. 5-22). Lymph Drainage The lymph vessels pass through many intermediate mesenteric nodes and finally reach the superior mesenteric nodes, which are situated around the origin of the superior mesenteric artery. Nerve Supply The nerves are derived from the sympathetic and parasympathetic (vagus) nerves from the superior mesenteric plexus. Clinical Notes Trauma to the Jejunum and Ileum Because of its extent and position, the small intestine is commonly damaged by trauma. The extreme mobility and elasticity permit the coils to move freely over one another in instances of blunt trauma. Small, penetrating injuries may self-seal as a result of the mucosa plugging up the hole and the contraction of the smooth muscle wall. Material from large wounds leaks freely into the peritoneal cavity. The presence of the vertebral column and the prominent anterior margin of the first sacral vertebra may provide a firm background for intestinal crushing in cases of midline crush injuries. Small-bowel contents have nearly a neutral pH and produce only slight chemical irritation to the peritoneum. Recognition of the Jejunum and Ileum A physician should be able to distinguish between the large and small intestine. He or she may be called on to examine a case of postoperative burst abdomen, where coils of gut are lying free in the bed. The macroscopic differences are described on page 227. Tumors and Cysts of the Mesentery of the Small Intestine The line of attachment of the small intestine to the posterior abdominal wall should be remembered. It extends from a point just to the left of the midline about 2 in. (5 cm) below the transpyloric plane (L1) downward to the right iliac fossa. A tumor or cyst of the mesentery, when palpated through the anterior abdominal wall, is more mobile in a direction at right angles to the line of attachment than along the line of attachment. Pain Fibers from the Jejunum and Ileum Pain fibers traverse the superior mesenteric sympathetic plexus and pass to the spinal cord via the splanchnic nerves. Referred pain from this segment of the gastrointestinal tract is felt in the dermatomes supplied by the 9th, 10th, and 11th thoracic nerves. Strangulation of a coil of small intestine in an inguinal hernia first gives rise to pain in the region of the umbilicus. Only later, when the parietal peritoneum of the hernial sac becomes inflamed, does the pain become more intense and localized to the inguinal region (see Abdominal Pain, page 281). Mesenteric Arterial Occlusion The superior mesenteric artery, a branch of the abdominal aorta, supplies an extensive territory of the gut, from halfway down the second part of the duodenum to the left colic flexure. Occlusion of the artery or one of its branches results in death of all or part of this segment of the gut. The occlusion may occur as the result of an embolus, a thrombus, an aortic dissection, or an abdominal aneurysm. Mesenteric Vein Thrombosis The superior mesenteric vein, which drains the same area of the gut supplied by the superior mesenteric artery, may undergo thrombosis after stasis of the venous bed. Cirrhosis of the liver with portal hypertension may predispose to this condition. Meckel’s Diverticulum Meckel’s diverticulum, a congenital anomaly of the ileum, is described on page 238. P.229
Large Intestine The large intestine extends from the ileum to the anus. It is divided into the cecum, appendix, ascending colon, transverse colon, descending colon, and sigmoid colon. The rectum and anal canal are considered in the sections on the pelvis and perineum. The primary function of the large intestine is the absorption of water and electrolytes and the storage of undigested material until it can be expelled from the body as feces. Cecum Location and Description The cecum is that part of the large intestine that lies below the level of the junction of the ileum with the large intestine (Figs. 5-32 and 5-33). It is a blind-ended pouch that is situated in the right iliac fossa. It is about 2.5 in. (6 cm) long and is completely covered with peritoneum. It possesses a considerable amount of mobility, although it does not have a mesentery. Attached to its posteromedial surface is the appendix. The presence of peritoneal folds in the vicinity of the cecum (Fig. 5-33) creates the superior ileocecal, the inferior ileocecal, and the retrocecal recesses (see page 208). As in the colon, the longitudinal muscle is restricted to three flat bands, the teniae coli, which converge on the base of the appendix and provide for it a complete longitudinal muscle coat (Fig. 5-33). The cecum is often distended with gas and can then be palpated through the anterior abdominal wall in the living patient. The terminal part of the ileum enters the large intestine at the junction of the cecum with the ascending colon. The opening is provided with two folds, or lips, which form the so-called ileocecal valve (see below). The appendix communicates with the cavity of the cecum through an opening located below and behind the ileocecal opening. Relations

  • Anteriorly: Coils of small intestine, sometimes part of the greater omentum, and the anterior abdominal wall in the right iliac region
  • Posteriorly: The psoas and the iliacus muscles, the femoral nerve, and the lateral cutaneous nerve of the thigh (Fig. 5-34). The appendix is commonly found behind the cecum.
  • Medially: The appendix arises from the cecum on its medial side (Fig. 5-33).

Blood Supply Arteries Anterior and posterior cecal arteries form the ileocolic artery, a branch of the superior mesenteric artery (Fig. 5-33). Veins The veins correspond to the arteries and drain into the superior mesenteric vein. P.230

Figure 5-32 Superior mesenteric artery and its branches. Note that this artery supplies blood to the gut from halfway down the second part of the duodenum to the distal third of the transverse colon (arrow).

Lymph Drainage The lymph vessels pass through several mesenteric nodes and finally reach the superior mesenteric nodes. Nerve Supply Branches from the sympathetic and parasympathetic (vagus) nerves form the superior mesenteric plexus. Ileocecal Valve A rudimentary structure, the ileocecal valve consists of two horizontal folds of mucous membrane that project around the orifice of the ileum. The valve plays little or no part in the prevention of reflux of cecal contents into the ileum. The circular muscle of the lower end of the ileum (called the ileocecal sphincter by physiologists) serves as a sphincter and controls the flow of contents from the ileum into the colon. The smooth muscle tone is reflexly increased when the cecum is distended; the hormone gastrin, which is produced by the stomach, causes relaxation of the muscle tone. Appendix Location and Description The appendix (Fig. 5-1) is a narrow, muscular tube containing a large amount of lymphoid tissue. It varies in length from 3 to 5 in. (8 to 13 cm). The base is attached to the posteromedial surface of the cecum about 1 in. (2.5 cm) below the ileocecal junction (Fig. 5-33). The remainder of the appendix is free. It has a complete peritoneal covering, which is attached to the mesentery of the small intestine by a short mesentery of its own, the mesoappendix. The mesoappendix contains the appendicular vessels and nerves. The appendix lies in the right iliac fossa, and in relation to the anterior abdominal wall its base is situated one third of the way up the line joining the right anterior superior iliac spine to the umbilicus (McBurney’s point). Inside the abdomen, the base of the appendix is easily found by identifying the teniae coli of the cecum and tracing them to the base of the appendix, where they converge to form a continuous longitudinal muscle coat (Figs. 5-32 and 5-33). P.231

Figure 5-33 Cecum and appendix. Note that the appendicular artery is a branch of the posterior cecal artery. The edge of the mesoappendix has been cut to show the peritoneal layers.
Figure 5-34 Posterior abdominal wall showing posterior relations of the kidneys and the colon.

P.232
Common Positions of the Tip of the Appendix The tip of the appendix is subject to a considerable range of movement and may be found in the following positions: (a) hanging down into the pelvis against the right pelvic wall, (b) coiled up behind the cecum, (c) projecting upward along the lateral side of the cecum, and (d) in front of or behind the terminal part of the ileum. The first and second positions are the most common sites. Blood Supply Arteries The appendicular artery is a branch of the posterior cecal artery (Fig. 5-33). Veins The appendicular vein drains into the posterior cecal vein. Lymph Drainage The lymph vessels drain into one or two nodes lying in the mesoappendix and then eventually into the superior mesenteric nodes. Nerve Supply The appendix is supplied by the sympathetic and parasympathetic (vagus) nerves from the superior mesenteric plexus. Afferent nerve fibers concerned with the conduction of visceral pain from the appendix accompany the sympathetic nerves and enter the spinal cord at the level of the 10th thoracic segment.

Figure 5-35 Abdominal cavity showing the terminal part of the ileum, the cecum, the appendix, the ascending colon, the right colic flexure, the left colic flexure, and the descending colon. Note the teniae coli and the appendices epiploicae.

Ascending Colon Location and Description The ascending colon is about 5 in. (13 cm) long and lies in the right lower quadrant (Fig. 5-35). It extends upward from the cecum to the inferior surface of the right lobe of the liver, where it turns to the left, forming the right colic flexure, and becomes continuous with the transverse colon. The peritoneum covers the front and the sides of the ascending colon, binding it to the posterior abdominal wall. Relations

  • Anteriorly: Coils of small intestine, the greater omentum, and the anterior abdominal wall (Figs. 5-2 and 5-3)
  • Posteriorly: The iliacus, the iliac crest, the quadratus lumborum, the origin of the transversus abdominis muscle, and the lower pole of the right kidney. The iliohypogastric and the ilioinguinal nerves cross behind it (Fig. 5-34).

P.233
Blood Supply Arteries The ileocolic and right colic branches of the superior mesenteric artery (Fig. 5-32) supply this area. Veins The veins correspond to the arteries and drain into the superior mesenteric vein. Lymph Drainage The lymph vessels drain into lymph nodes lying along the course of the colic blood vessels and ultimately reach the superior mesenteric nodes. Nerve Supply Sympathetic and parasympathetic (vagus) nerves from the superior mesenteric plexus supply this area of the colon. Transverse Colon Location and Description The transverse colon is about 15 in. (38 cm) long and extends across the abdomen, occupying the umbilical region. It begins at the right colic flexure below the right lobe of the liver (Fig. 5-4) and hangs downward, suspended by the transverse mesocolon from the pancreas (Fig. 5-6). It then ascends to the left colic flexure below the spleen. The left colic flexure is higher than the right colic flexure and is suspended from the diaphragm by the phrenicocolic ligament (Fig. 5-35).

Figure 5-36 Inferior mesenteric artery and its branches. Note that this artery supplies the large bowel from the distal third of the transverse colon to halfway down the anal canal. It anastomoses with the middle colic branch of the superior mesenteric artery (arrow).

The transverse mesocolon, or mesentery of the transverse colon, suspends the transverse colon from the anterior border of the pancreas (Fig. 5-6). The mesentery is attached to the superior border of the transverse colon, and the posterior layers of the greater omentum are attached to the inferior border (Fig. 5-6). Because of the length of the transverse mesocolon, the position of the transverse colon is extremely variable and may sometimes reach down as far as the pelvis. Relations

  • Anteriorly: The greater omentum and the anterior abdominal wall (umbilical and hypogastric regions) (Fig. 5-6)
  • Posteriorly: The second part of the duodenum, the head of the pancreas, and the coils of the jejunum and ileum (Fig. 5-35)

Blood Supply Arteries The proximal two thirds are supplied by the middle colic artery, a branch of the superior mesenteric artery (Fig. 5-32). The distal third is supplied by the left colic artery, a branch of the inferior mesenteric artery (Fig. 5-36). P.234
Veins The veins correspond to the arteries and drain into the superior and inferior mesenteric veins. Lymph Drainage The proximal two thirds drain into the colic nodes and then into the superior mesenteric nodes; the distal third drains into the colic nodes and then into the inferior mesenteric nodes. Nerve Supply The proximal two thirds are innervated by sympathetic and vagal nerves through the superior mesenteric plexus; the distal third is innervated by sympathetic and parasympathetic pelvic splanchnic nerves through the inferior mesenteric plexus. Descending Colon Location and Description The descending colon is about 10 in. (25 cm) long and lies in the left upper and lower quadrants (Fig. 5-35). It extends downward from the left colic flexure, to the pelvic brim, where it becomes continuous with the sigmoid colon. (For the sigmoid colon, see page 338.) The peritoneum covers the front and the sides and binds it to the posterior abdominal wall. Relations

  • Anteriorly: Coils of small intestine, the greater omentum, and the anterior abdominal wall (Figs. 5-2 and 5-3)
  • Posteriorly: The lateral border of the left kidney, the origin of the transversus abdominis muscle, the quadratus lumborum, the iliac crest, the iliacus, and the left psoas. The iliohypogastric and the ilioinguinal nerves, the lateral cutaneous nerve of the thigh, and the femoral nerve (Fig. 5-34) also lie posteriorly.

Blood Supply Arteries The left colic and the sigmoid branches of the inferior mesenteric artery (Fig. 5-36) supply this area. Veins The veins correspond to the arteries and drain into the inferior mesenteric vein. Lymph Drainage Lymph drains into the colic lymph nodes and the inferior mesenteric nodes around the origin of the inferior mesenteric artery. Nerve Supply The nerve supply is the sympathetic and parasympathetic pelvic splanchnic nerves through the inferior mesenteric plexus. Clinical Notes Colonoscopy Since colorectal cancer is a leading cause of death in the Western world, colonoscopy is now being extensively used for early detection of malignant tumors. In this procedure, the mucous membrane of the colon can be directly visualized through an elongated flexible tube, or endoscope. Following a thorough washing out of the large bowel, the patient is sedated, and the tube is gently inserted into the anal canal. The interior of the large bowel can be observed from the anus to the cecum (Fig. 5-37). Photographs of suspicious areas, such as polyps, can be taken and biopsy specimens can be removed for pathologic examination. Although a relatively expensive procedure, it provides a more complete screening examination for colorectal cancer than combined fecal occult blood testing and the examination of the distal colon with sigmoidoscopy (see page 339). Variability of Position of the Appendix The inconstancy of the position of the appendix should be borne in mind when attempting to diagnose an appendicitis. A retrocecal appendix, for example, may lie behind a cecum distended with gas, and thus it may be difficult to elicit tenderness on palpation in the right iliac region. Irritation of the psoas muscle, conversely, may cause the patient to keep the right hip joint flexed. An appendix hanging down in the pelvis may result in absent abdominal tenderness in the right lower quadrant, but deep tenderness may be experienced just above the symphysis pubis. Rectal or vaginal examination may reveal tenderness of the peritoneum in the pelvis on the right side. Predisposition of the Appendix to Infection The following factors contribute to the appendix’s predilection to infection:

  • It is a long, narrow, blind-ended tube, which encourages stasis of large-bowel contents.
  • It has a large amount of lymphoid tissue in its wall.
  • The lumen has a tendency to become obstructed by hardened intestinal contents (enteroliths), which leads to further stagnation of its contents.

Predisposition of the Appendix to Perforation The appendix is supplied by a long small artery that does not anastomose with other arteries. The blind end of the appendix is supplied by the terminal branches of the appendicular artery. Inflammatory edema of the appendicular wall compresses the blood supply to the appendix and often leads to thrombosis of the appendicular artery. These conditions commonly result in necrosis or gangrene of the appendicular wall, with perforation. Perforation of the appendix or transmigration of bacteria through the inflamed appendicular wall results in infection of the peritoneum of the greater sac. The part that the greater omentum may play in arresting the spread of the peritoneal infection is described on page 213. Pain of Appendicitis Visceral pain in the appendix is produced by distention of its lumen or spasm of its muscle. The afferent pain fibers enter the spinal cord at the level of the 10th thoracic segment, and a vague referred pain is felt in the region of the umbilicus. Later, the pain shifts to where the inflamed appendix irritates the parietal peritoneum. Here the pain is precise, severe, and localized (see Abdominal Pain, page 281).

Figure 5-37 Series of the interior of the large bowel taken during a colonoscopy procedure. A. The rectal mucosa shows a small benign polyp (arrowhead). B. The sigmoid mucous membrane shows evidence of a mild diverticulosis. Arrowheads indicate the entrances into the mucosal pouches. C. The splenic flexure is normal. Note the light reflections from the drops of mucus on the mucous membrane. D. The transverse colon shows the characteristic normal folds or ridges (arrowheads) between the sacculations of the wall of the colon. E. The ileocecal valve shows the upper lip (arrowheads) of the valve, which has a normal appearance. F. Finally, the mucous membrane lining the inferior wall or floor of the cecum looks normal. (Courtesy of M.H. Brand.)

Trauma of the Cecum and Colon Blunt or penetrating injuries to the colon occur. Blunt injuries most commonly occur where mobile parts of the colon (transverse and sigmoid) join the fixed parts (ascending and descending). Penetrating injuries following stab wounds are common. The multiple anatomic relationships of the different parts of the colon explain why isolated colonic trauma is unusual. Cancer of the Large Bowel Cancer of the large bowel is relatively common in persons older than 50 years. The growth is restricted to the bowel wall for a considerable time before it spreads via the lymphatics. Bloodstream spread via the portal circulation to the liver occurs late. If a diagnosis is made early and a partial colectomy is performed, accompanied by removal of the lymph vessels and lymph nodes draining the area, then a cure can be anticipated. Diverticulosis Diverticulosis of the colon is a common clinical condition. It consists of a herniation of the lining mucosa through the circular muscle between the teniae coli and occurs at points where the circular muscle is weakest—that is, where the blood vessels pierce the muscle (Fig. 5-38). The common site for herniation is shown in Figure 5-38. Cecostomy and Colostomy Because of the anatomic mobility of the cecum, transverse colon, and sigmoid colon, they may be brought to the surface through a small opening in the anterior abdominal wall. If the cecum or transverse colon is then opened, the bowel contents may be allowed to drain by this route. These procedures are referred to as cecostomy or colostomy, respectively, and are used to relieve large-bowel obstructions. Volvulus Because of its extreme mobility, the sigmoid colon sometimes rotates around its mesentery. This may correct itself spontaneously or the rotation may continue until the blood supply of the gut is cut off completely. Intussusception Intussusception is the telescoping of a proximal segment of the bowel into the lumen of an adjoining distal segment. Needless to say, there is a grave risk of cutting off the blood supply to the gut and developing gangrene. It is common in children. Ileocolic, colocolic, and ileoileal forms do occur, but ileocolic is the most common. The high incidence in children may be caused by the relatively large size of the large bowel compared with the small intestine at this time of life. Another factor may be the possible swelling of Peyer’s patches secondary to infection. In the latter case, the swollen patch protrudes into the lumen and violent peristalsis of the ileal wall tries to pass it distally along the gut lumen. P.235
P.236
P.237

Figure 5-38 Blood supply to the colon (A) and formation of the diverticulum (B). Note the passage of the mucosal diverticulum through the muscle coat along the course of the artery.

Embryologic Notes Development of the Digestive System The digestive tube is formed from the yolk sac. The entoderm forms the epithelial lining, and the splanchnic mesenchyme forms the surrounding muscle and serous coats. The developing gut is divided into the foregut, midgut, and hindgut (Fig. 5-39). Development of the Esophagus The esophagus develops from the narrow part of the foregut that succeeds the pharynx (Fig. 5-39). At first, it is a short tube, but when the heart and diaphragm descend, it elongates rapidly. Atresia of the Esophagus Atresia of the esophagus, with and without fistula, with the trachea is considered in detail on page 99. Esophageal Stenosis Esophageal stenosis is a narrowing of the lumen of the esophagus, which commonly occurs in the lower part. It is treated by dilatation. Congenital Short Esophagus Abnormal shortness of the esophagus is caused by an esophageal hiatus hernia in the diaphragm. Stomach contents flow into the esophagus, resulting in esophagitis. Development of the Stomach The stomach develops as a dilatation of the foregut (Fig. 5-40). To begin with, it has a ventral and dorsal mesentery. Very active growth takes place along the dorsal border, which becomes convex and forms the greater curvature. The anterior border becomes concave and forms the lesser curvature. The fundus appears as a dilatation at the upper end of the stomach. At this stage, the stomach has a right and left surface to which the right and left vagus nerves are attached, respectively (Fig. 5-40). With the great growth of the right lobe of the liver, the stomach is gradually rotated to the right so that the left surface becomes anterior and the right surface, posterior. The ventral and dorsal mesenteries now change position as a result of rotation of the stomach, and they form the omenta and various peritoneal ligaments. The pouch of peritoneum behind the stomach is known as the lesser sac. Congenital Hypertrophic Pyloric Stenosis Hypertrophic pyloric stenosis is a relatively common emergency in infants between the ages of 3 and 6 weeks. The child ejects the stomach contents with considerable force. The exact cause of the stenosis is unknown, although evidence suggests that the number of autonomic ganglion cells in the stomach wall is fewer than normal. This possibility leads to prenatal neuromuscular incoordination and localized muscular hypertrophy and hyperplasia of the pyloric sphincter. It is much more common in male children. Development of the Duodenum The duodenum is formed from the most caudal portion of the foregut and the most cephalic end of the midgut. This region rapidly grows to form a loop. At this time, the duodenum has a mesentery that extends to the posterior abdominal wall and is part of the dorsal mesentery. A small part of the ventral mesentery is also attached to the ventral border of the first part of the duodenum and the upper half of the second part of the duodenum. When the stomach rotates, the duodenal loop is forced to rotate to the right, where the second, third, and fourth parts adhere to the posterior abdominal wall. Now the peritoneum behind the duodenum disappears. However, some smooth muscle and fibrous tissue that belong to the dorsal mesentery remain as the suspensory ligament of the duodenum (ligament of Treitz), and this fixes the terminal part of the duodenum and prevents it from moving inferiorly (Fig. 5-41). The liver and pancreas arise as entodermal buds from the developing duodenum. Atresia and Stenosis During the development of the duodenum, the lining cells proliferate at such a rate that the lumen becomes completely obliterated. Later, as a result of degeneration of these cells, the gut becomes recanalized. Failure of recanalization could produce atresia or stenosis. Different forms of duodenal atresia and stenosis are shown in Figure 5-42. Vomiting is the most common presenting symptom, and the vomitus usually is bile stained. Surgical treatment during the first few days of life is essential. Development of the Jejunum, Ileum, Cecum, Appendix, Ascending Colon, and Proximal Two Thirds of the Transverse Colon Distal to the duodenum, the small intestine and the large intestine, as far as the distal third of the transverse colon, develop from the midgut. The midgut increases rapidly in length and forms a loop to the apex, on which is attached the vitelline duct; this duct passes through the widely open umbilicus (Fig. 5-39). At the same time, the dorsal mesentery elongates, and passing through it from the aorta to the yolk sac are the vitelline arteries. These arteries now fuse to form the superior mesenteric artery, which supplies the midgut and its derivatives. The rapidly growing liver and kidneys now encroach on the abdominal cavity, causing the midgut loop to herniate into the umbilical cord. A diverticulum appears at the caudal end of the bowel loop, and this forms the cecum. At first the diverticulum is conical; later the upper part expands and forms the cecum, while the lower part remains rudimentary and forms the appendix (Fig. 5-43). After birth, the wall of the cecum grows unequally, and the appendix comes to lie on its medial side. While the loop of gut is in the umbilical cord, its cephalic limb becomes greatly elongated and coiled and forms the future jejunum and greater part of the ileum. The caudal limb of the loop also increases in length, but it remains uncoiled and forms the future distal part of the ileum, the cecum, the appendix, the ascending colon, and the proximal two thirds of the transverse colon. Rotation of the Midgut Loop in the Umbilical Cord and Its Return to the Abdominal Cavity While in the umbilical cord, the midgut rotates around an axis formed by the superior mesenteric artery and the vitelline duct. As one views the embryo from the anterior aspect, a counterclockwise rotation of approximately 90° occurs (Fig. 5-44). Later, as the gut returns to the abdominal cavity, the midgut rotates counterclockwise an additional 180°. Thus, a total rotation of 270° counterclockwise has occurred (Fig. 5-45). The rotation of the gut results in part of the large intestine (transverse colon) coming in front of the superior mesenteric artery and the second part of the duodenum; the third part of the duodenum comes to lie behind the artery. The cecum and appendix come into close contact with the right lobe of the liver. Later, the cecum and appendix descend into the right iliac fossa so that the ascending colon and right colic flexure are formed. Thus, the rotation of the gut has resulted in the large gut coming to lie laterally and encircle the centrally placed small gut. The primitive mesenteries of the duodenum, ascending and descending colons now fuse with the parietal peritoneum on the posterior abdominal wall. This explains how these parts of the developing gut become retroperitoneal. The primitive mesenteries of the jejunum and ileum, the transverse colon, and the sigmoid colon persist as the mesentery of the small intestine, the transverse mesocolon, and the sigmoid mesocolon, respectively. The rotation of the stomach and duodenum to the right is largely brought about by the great growth of the right lobe of the liver. The left surface of the stomach becomes anterior, and the right surface becomes posterior. A pouch of peritoneum becomes located behind the stomach and is called the lesser sac. Fate of the Vitelline Duct The midgut is at first connected with the yolk sac by the vitelline duct. By the time the gut returns to the abdominal cavity, the duct becomes obliterated and severs its connection with the gut. Development of the Left Colic Flexure, Descending Colon, Sigmoid Colon, Rectum, and Upper Half of the Anal Canal The left colic flexure, descending colon, sigmoid colon, rectum, and upper half of the anal canal are developed from the hindgut (see page 237). Diverticula of the Intestine All coats of the intestinal wall are found in the wall of a congenital diverticulum. In the duodenum, diverticula are found on the medial wall of the second and third parts (Fig. 5-42). Usually, these are symptomless. Jejunal diverticula occasionally occur and usually give rise to no symptoms. For Meckel’s diverticulum of the ileum, see next column. A diverticulum of the cecum is commonly situated on the medial side of the cecum close to the ileocecal valve. It may be subject to acute inflammation and then is confused with appendicitis. Diverticula of the colon are acquired, not congenital (see page 236). Atresia and Stenosis of the Intestine The most common site of an atretic or stenotic obstruction is in the duodenum (see previous page). The next most common sites are the ileum and jejunum, respectively (Fig. 5-42). Frequently, the obstruction occurs at multiple sites. The cause is possibly the failure of the lumen to become recanalized after it has been blocked by epithelial proliferation of the cells of the mucous membrane. Other causes have been suggested, such as vascular damage associated with twisting or volvulus of the intestine. Persistent bile-stained vomiting occurs from birth. Surgical relief of the obstruction should be carried out as soon as possible. Duplication of the Digestive System In duplication of the digestive system, the normal degeneration of the mucous membrane cells, which have proliferated to temporarily block the lumen, occurs at two sites simultaneously instead of at one. In this way, two lumina are formed side by side. The additional segment of bowel should be removed as soon as possible, since it may cause obstruction or be the site of hemorrhage or perforation. Arrested Rotation or Malrotation of the Midgut Loop Complete Absence of Rotation or Incomplete Rotation Complete absence of rotation is rare. In cases of incomplete rotation no further rotation occurs after the initial counterclockwise rotation of 90° in the umbilical cord. Thus, the duodenum, jejunum, and ileum remain on the right side of the abdomen, and the cecum and colon are on the left side of the abdomen (Fig. 5-42). In other cases, a counterclockwise rotation of 180° occurs, and although the duodenum may take up its correct position posterior to the superior mesenteric artery, the cecum comes to lie anterior and to the left of the duodenum. Abnormal adhesions form, which run across the anterior surface of the duodenum and cause obstruction to its second part. Malrotation of the Midgut Loop Counterclockwise rotation of 90° followed by clockwise rotation of 90° or 180° may occur. In these cases, the duodenum comes to lie anterior to the superior mesenteric artery, and the colon may come to lie anterior to the mesentery of the small intestine. Repeated vomiting is usually the presenting symptom and is caused by duodenal obstruction. Surgical correction of the incomplete rotation or malrotation of the gut is performed, and all adhesions are divided. Persistence of the Vitellointestinal Duct The vitelline duct in the early embryo connects the developing gut to the yolk sac (Fig. 5-46). Normally, as development proceeds, the duct is obliterated, severs its connection with the intestine, and disappears. Persistence of the vitellointestinal duct can result in an umbilical fistula (see Fig. 4-38). If the duct remains as a fibrous band, a loop of small intestine can become wrapped around it, causing intestinal obstruction (see Fig. 4-38). Meckel’s Diverticulum Meckel’s diverticulum, a congenital anomaly, represents a persistent portion of the vitellointestinal duct. The diverticulum is located on the antimesenteric border of the ileum about 2 ft (61 cm) from the ileocecal junction. It is about 2 in. (5 cm) long and occurs in about 2% of individuals. The diverticulum is important clinically, since it may possess a small area of gastric mucosa, and bleeding may occur from a “gastric” ulcer in its mucous membrane. Moreover, the pain from this ulcer may be confused with the pain from appendicitis. Should a fibrous band connect the diverticulum to the umbilicus, a loop of small bowel may become wrapped around it, causing intestinal obstruction. Undescended Cecum and Appendix In cases of undescended cecum and appendix, an inflammation of the appendix would give rise to tenderness in the right hypochondrium, which may lead to a mistaken diagnosis of inflammation of the gallbladder. Anomalies of the Appendix Agenesis of the appendix (failure to develop) is extremely rare; however, a few examples of double appendix have been reported (Fig. 5-42). The possibility of left-sided appendix in individuals with transposition of thoracic and abdominal viscera or in cases of arrested rotation of the midgut should always be remembered (Fig. 5-42). Anomalies of the Colon The congenital anomaly of undescended cecum or failure of rotation of the gut so that the cecum lies in the left iliac fossa may give rise to confusion in diagnosis. The pain of appendicitis, for example, although initially starting in the umbilical region, may shift not to the right iliac fossa, but to the right upper quadrant or to the left lower quadrant. P.238
P.239

Figure 5-39 The foregut, midgut, and hindgut. The positions of the ventral and dorsal mesenteries, the hepatic bud, and the ventral and dorsal pancreatic buds are also shown.
Figure 5-40 Development of the stomach in relation to the ventral and dorsal mesenteries. Note how the stomach rotates so that the left vagus nerve comes to lie on the anterior surface of the stomach. Note also the position of the lesser sac.

P.240

Figure 5-41 The development of the pancreas and the extrahepatic biliary apparatus.

Blood Supply of the Gastrointestinal Tract Arterial Supply The arterial supply to the gut and its relationship to the development of the different parts of the gut are illustrated diagrammatically in Figure 5-46. The celiac artery is the artery of the foregut and supplies the gastrointestinal tract from the lower one third of the esophagus down as far as the middle of the second part of the duodenum. The superior mesenteric artery is the artery of the midgut and supplies the gastrointestinal tract from the middle of the second part of the duodenum as far as the distal one third of the transverse colon. The inferior mesenteric artery is the artery of the hindgut and supplies the large intestine from the distal one third of the transverse colon to halfway down the anal canal. Celiac Artery The celiac artery or trunk is very short and arises from the commencement of the abdominal aorta at the level of the 12th thoracic vertebra (Fig. 5-20). It is surrounded by the celiac plexus and lies behind the lesser sac of peritoneum. It has three terminal branches: the left gastric, splenic, and hepatic arteries. Left Gastric Artery The small left gastric artery runs to the cardiac end of the stomach, gives off a few esophageal branches, then turns to the right along the lesser curvature of the stomach. It anastomoses with the right gastric artery (Fig. 5-20). Splenic Artery The large splenic artery runs to the left in a wavy course along the upper border of the pancreas and behind the stomach (Fig. 5-4). On reaching the left kidney the artery enters the splenicorenal ligament and runs to the hilum of the spleen (Fig. 5-11). Branches

  • Pancreatic branches
  • The left gastroepiploic artery arises near the hilum of the spleen and reaches the greater curvature of the stomach in the gastrosplenic omentum. It passes to the right P.241
    P.242
    P.243
    along the greater curvature of the stomach between the layers of the greater omentum. It anastomoses with the right gastroepiploic artery (Fig. 5-20).
    Figure 5-42 Some common congenital anomalies of the intestinal tract. 1–3. Congenital atresias of the small intestine. 4. Diverticulum of the duodenum or jejunum. 5. Mesenteric cyst of the small intestine. 6. Absence of the appendix. 7. Double appendix. 8. Malrotation of the gut, with the appendix lying in the left iliac fossa. For Meckel’s diverticulum, see Figure 4-38.
    Figure 5-43 Stages in the development of the cecum and appendix. The final stages of development (stages 4, 5, and 6) take place after birth.
    Figure 5-44 Left side views of the counterclockwise 90° rotation of the midgut loop while it is in the extraembryonic coelom in the umbilical cord.
    Figure 5-45 Left side views (A, B) of the counterclockwise 180° rotation of the midgut loop as it is withdrawn into the abdominal cavity. C. The descent of the cecum takes place later.
    Figure 5-46 Formation of the midgut loop (shaded). Note how the superior mesenteric artery and vitelline duct form an axis for the future rotation of the midgut loop.
  • The short gastric arteries, five or six in number, arise from the end of the splenic artery and reach the fundus of the stomach in the gastrosplenic omentum. They anastomose with the left gastric artery and the left gastroepiploic artery (Fig. 5-20).

Hepatic Artery The medium-size hepatic artery* runs forward and to the right and then ascends between the layers of the lesser omentum (Figs. 5-7 and 5-11). It lies in front of the opening into the lesser sac and is placed to the left of the bile duct and in front of the portal vein. At the porta hepatis it divides into right and left branches to supply the corresponding lobes of the liver. Branches

  • The right gastric artery arises from the hepatic artery at the upper border of the pylorus and runs to the left in the lesser omentum along the lesser curvature of the stomach. It anastomoses with the left gastric artery (Fig. 5-20).
  • The gastroduodenal artery is a large branch that descends behind the first part of the duodenum. It divides into the right gastroepiploic artery that runs along the greater curvature of the stomach between the layers of the greater omentum and the superior pancreaticoduodenal artery that descends between the second part of the duodenum and the head of the pancreas (Figs. 5-4 and 5-20).
  • The right and left hepatic arteries enter the porta hepatis. The right hepatic artery usually gives off the cystic artery, which runs to the neck of the gallbladder (Fig. 5-47).

Superior Mesenteric Artery The superior mesenteric artery supplies the distal part of the duodenum, the jejunum, the ileum, the cecum, the appendix, the ascending colon, and most of the transverse colon. It arises from the front of the abdominal aorta just below the celiac artery (Fig. 5-32) and runs downward and to the right behind the neck of the pancreas and in front of the third part of the duodenum. It continues downward to the right between the layers of the mesentery of the small intestine and ends by anastomosing with the ileal branch of its own ileocolic branch. Branches

  • The inferior pancreaticoduodenal artery passes to the right as a single or double branch along the upper border of the third part of the duodenum and the head of the pancreas. It supplies the pancreas and the adjoining part of the duodenum. P.244
    Figure 5-47 Structures entering and leaving the porta hepatis.
  • The middle colic artery runs forward in the transverse mesocolon to supply the transverse colon and divides into right and left branches.
  • The right colic artery is often a branch of the ileocolic artery. It passes to the right to supply the ascending colon and divides into ascending and descending branches.
  • The ileocolic artery passes downward and to the right. It gives rise to a superior branch that anastomoses with the right colic artery and an inferior branch that anastomoses with the end of the superior mesenteric artery. The inferior branch gives rise to the anterior and posterior cecal arteries; the appendicular artery is a branch of the posterior cecal artery (Fig. 5-33).
  • The jejunal and ileal branches are 12 to 15 in number and arise from the left side of the superior mesenteric artery (Fig. 5-32). Each artery divides into two vessels, which unite with adjacent branches to form a series of arcades. Branches from the arcades divide and unite to form a second, third, and fourth series of arcades. Fewer arcades supply the jejunum than supply the ileum. From the terminal arcades, small straight vessels supply the intestine.

Inferior Mesenteric Artery The inferior mesenteric artery supplies the distal third of the transverse colon, the left colic flexure, the descending colon, the sigmoid colon, the rectum, and the upper half of the anal canal. It arises from the abdominal aorta about 1.5 in. (3.8 cm) above its bifurcation (Fig. 5-36). The artery runs downward and to the left and crosses the left common iliac artery. Here, it becomes the superior rectal artery. Branches

  • The left colic artery runs upward and to the left and supplies the distal third of the transverse colon, the left colic flexure, and the upper part of the descending colon. It divides into ascending and descending branches.
  • The sigmoid arteries are two or three in number and supply the descending and sigmoid colon.
  • The superior rectal artery is a continuation of the inferior mesenteric artery as it crosses the left common iliac artery. It descends into the pelvis behind the rectum. The artery supplies the rectum and upper half of the anal canal and anastomoses with the middle rectal and inferior rectal arteries.

Marginal Artery The anastomosis of the colic arteries around the concave margin of the large intestine forms a single arterial trunk called the marginal artery. This begins at the ileocecal junction, where it anastomoses with the ileal branches of the superior mesenteric artery, and it ends where it anastomoses less freely with the superior rectal artery (Fig. 5-36). Embryologic Notes Explanation for the Blood Supply to the Gastrointestinal Tract Foregut Arteries The cephalic end of the foregut (which includes the pharynx) and the cervical and thoracic portions of the esophagus are supplied by the ascending pharyngeal arteries, palatine arteries, superior and inferior thyroid arteries, bronchial arteries, and esophageal branches from the aorta. The caudal end of the foregut (which includes the distal third of the esophagus, the stomach, and the proximal half of the duodenum) is supplied by a number of vessels that fuse to form a single trunk, the celiac artery (Fig. 5-46). It is interesting to note that this artery also supplies the liver and pancreas, which are glandular derivatives of this part of the gut. The spleen is also supplied by the same artery, which is not surprising, since this organ develops in the dorsal mesentery of the foregut; the artery to the spleen runs in the splenicorenal ligament. Midgut Artery The midgut, which extends from halfway along the second part of the duodenum to the left colic flexure, is supplied by the superior mesenteric artery, which represents the fused pair of vitelline arteries (Fig. 5-46). Hindgut Artery The hindgut, which extends from the left colic flexure to halfway down the anal canal, is supplied by the inferior mesenteric artery (Fig. 5-46). This represents a number of ventral branches of the aorta that fuse to form a single artery. P.245
Venous Drainage The venous blood from the greater part of the gastrointestinal tract and its accessory organs drains to the liver by the portal venous system. The proximal tributaries drain directly into the portal vein, but the veins forming the distal tributaries correspond to the branches of the celiac artery and the superior and inferior mesenteric arteries. Portal Vein (Hepatic Portal Vein) The portal vein (Fig. 5-22) drains blood from the abdominal part of the gastrointestinal tract from the lower third of the esophagus to halfway down the anal canal; it also drains blood from the spleen, pancreas, and gallbladder. The portal vein enters the liver and breaks up into sinusoids, from which blood passes into the hepatic veins that join the inferior vena cava. The portal vein is about 2 in. (5 cm) long and is formed behind the neck of the pancreas by the union of the superior mesenteric and splenic veins (Fig. 5-48). It ascends to the right, behind the first part of the duodenum, and enters the lesser omentum (Figs. 5-7 and 5-11). It then runs upward in front of the opening into the lesser sac to the porta hepatis, where it divides into right and left terminal branches.

Figure 5-48 Formation of the portal vein behind the neck of the pancreas.

The portal circulation begins as a capillary plexus in the organs it drains and ends by emptying its blood into sinusoids within the liver. For the relations of the portal vein in the lesser omentum, see Figures 5-7 and 5-11. Tributaries of the Portal Vein The tributaries of the portal vein are the splenic vein, superior mesenteric vein, left gastric vein, right gastric vein, and cystic veins.

  • Splenic vein: This vein leaves the hilum of the spleen and passes to the right in the splenicorenal ligament. It unites with the superior mesenteric vein behind the neck of the pancreas to form the portal vein (Fig. 5-48). It receives the short gastric, left gastroepiploic, inferior mesenteric, and pancreatic veins.
  • Inferior mesenteric vein: This vein ascends on the posterior abdominal wall and joins the splenic vein behind the body of the pancreas (Fig. 5-48). It receives the superior rectal veins, the sigmoid veins, and the left colic vein.
  • Superior mesenteric vein: This vein ascends in the root of the mesentery of the small intestine. It passes in front of the third part of the duodenum and joins the splenic vein behind the neck of the pancreas (Fig. 5-48). It receives the jejunal, ileal, ileocolic, right colic, middle colic, inferior pancreaticoduodenal, and right gastroepiploic veins.
  • Left gastric vein: This vein drains the left portion of the lesser curvature of the stomach and the distal part of the esophagus. It opens directly into the portal vein (Fig. 5-22).
  • Right gastric vein: This vein drains the right portion of the lesser curvature of the stomach and drains directly into the portal vein (Fig. 5-22).
  • Cystic veins: These veins either drain the gallbladder directly into the liver or join the portal vein (Fig. 5-22).

Clinical Notes Portal–Systemic Anastomoses Under normal conditions, the portal venous blood traverses the liver and drains into the inferior vena cava of the systemic venous circulation by way of the hepatic veins. This is the direct route. However, other, smaller communications exist between the portal and systemic systems, and they become important when the direct route becomes blocked (Fig. 5-49). These communications are as follows:

  • At the lower third of the esophagus, the esophageal branches of the left gastric vein (portal tributary) anastomose with the esophageal veins draining the middle third of the esophagus into the azygos veins (systemic tributary).
  • Halfway down the anal canal, the superior rectal veins (portal tributary) draining the upper half of the anal canal anastomose with the middle and inferior rectal veins (systemic tributaries), which are tributaries of the internal iliac and internal pudendal veins, respectively.
  • The paraumbilical veins connect the left branch of the portal vein with the superficial veins of the anterior abdominal wall (systemic tributaries). The paraumbilical veins travel in the falciform ligament and accompany the ligamentum teres.
  • The veins of the ascending colon, descending colon, duodenum, pancreas, and liver (portal tributary) anastomose with the renal, lumbar, and phrenic veins (systemic tributaries).

Portal Hypertension Portal hypertension is a common clinical condition; thus, the list of portal–systemic anastomoses should be remembered. Enlargement of the portal–systemic connections is frequently accompanied by congestive enlargement of the spleen. Portacaval shunts for the treatment of portal hypertension may involve the anastomosis of the portal vein, because it lies within the lesser omentum, to the anterior wall of the inferior vena cava behind the entrance into the lesser sac. The splenic vein may be anastomosed to the left renal vein after removing the spleen. Blood Flow in the Portal Vein and Malignant Disease The portal vein conveys about 70% of the blood to the liver. The remaining 30% is oxygenated blood, which passes to the liver via the hepatic artery. The wide angle of union of the splenic vein with the superior mesenteric vein to form the portal vein leads to streaming of the blood flow in the portal vein. The right lobe of the liver receives blood mainly from the intestine, whereas the left lobe plus the quadrate and caudate lobes receive blood from the stomach and the spleen. This distribution of blood may explain the distribution of secondary malignant deposits in the liver. P.246
Differences Between the Small and Large Intestine External Differences (Fig. 5-50)

  • The small intestine (with the exception of the duodenum) is mobile, whereas the ascending and descending parts of the colon are fixed.
  • The caliber of the full small intestine is smaller than that of the filled large intestine.
  • The small intestine (with the exception of the duodenum) has a mesentery that passes downward across the midline into the right iliac fossa.
  • The longitudinal muscle of the small intestine forms a continuous layer around the gut. In the large intestine (with the exception of the appendix) the longitudinal muscle is collected into three bands, the teniae coli.
  • The small intestine has no fatty tags attached to its wall. The large intestine has fatty tags, called the appendices epiploicae.
  • The wall of the small intestine is smooth, whereas that of the large intestine is sacculated.

Internal Differences (Fig. 5-50)

  • The mucous membrane of the small intestine has permanent folds, called plicae circulares, which are absent in the large intestine.
  • The mucous membrane of the small intestine has villi, which are absent in the large intestine.
  • Aggregations of lymphoid tissue called Peyer’s patches are found in the mucous membrane of the small intestine; these are absent in the large intestine.

Accessory Organs of the Gastrointestinal Tract Liver Location and Description The liver is the largest gland in the body and has a wide variety of functions. Three of its basic functions are production and secretion of bile, which is passed into the intestinal tract; involvement in many metabolic activities related to carbohydrate, fat, and protein metabolism; and filtration of the blood, removing bacteria and other foreign particles that have gained entrance to the blood from the lumen of the intestine. The liver synthesizes heparin, an anticoagulant substance, and has an important detoxicating function. It produces bile pigments from the hemoglobin of worn-out red blood corpuscles and secretes bile salts; these together are conveyed to the duodenum by the biliary ducts. The liver is soft and pliable and occupies the upper part of the abdominal cavity just beneath the diaphragm (Fig. 5-1). The greater part of the liver is situated under cover of the right costal margin, and the right hemidiaphragm separates it from the pleura, lungs, pericardium, and heart. The liver extends to the left to reach the left hemidiaphragm. The convex upper surface of the liver is molded to the undersurface of the domes of the diaphragm. The posteroinferior, P.247
or visceral surface, is molded to adjacent viscera and is therefore irregular in shape; it lies in contact with the abdominal part of the esophagus, the stomach, the duodenum, the right colic flexure, the right kidney and suprarenal gland, and the gallbladder.

Figure 5-49 Important portal–systemic anastomoses.

The liver may be divided into a large right lobe and a small left lobe by the attachment of the peritoneum of the falciform ligament (Fig. 5-8). The right lobe is further divided into a quadrate lobe and a caudate lobe by the presence of the gallbladder, the fissure for the ligamentum teres, the inferior vena cava, and the fissure for the ligamentum venosum. Experiments have shown that, in fact, the quadrate and caudate lobes are a functional part of the left lobe of the liver. Thus, the right and left branches of the hepatic artery and portal vein, and the right and left hepatic ducts, are distributed to the right lobe and the left lobe (plus quadrate plus caudate lobes), respectively. Apparently, the two sides overlap very little. The porta hepatis, or hilum of the liver, is found on the posteroinferior surface and lies between the caudate and quadrate lobes (Figs. 5-8 and 5-9). The upper part of the free edge of the lesser omentum is attached to its margins. In it P.248
lie the right and left hepatic ducts, the right and left branches of the hepatic artery, the portal vein, and sympathetic and parasympathetic nerve fibers (Fig. 5-47). A few hepatic lymph nodes lie here; they drain the liver and gallbladder and send their efferent vessels to the celiac lymph nodes.

Figure 5-50 Some external and internal differences between the small and the large intestine.

The liver is completely surrounded by a fibrous capsule but only partially covered by peritoneum. The liver is made up of liver lobules. The central vein of each lobule is a tributary of the hepatic veins. In the spaces between the lobules are the portal canals, which contain branches of the hepatic artery, portal vein, and a tributary of a bile duct (portal triad). The arterial and venous blood passes between the liver cells by means of sinusoids and drains into the central vein. Important Relations

  • Anteriorly: Diaphragm, right and left costal margins, right and left pleura and lower margins of both lungs, xiphoid process, and anterior abdominal wall in the subcostal angle
  • Posteriorly: Diaphragm, right kidney, hepatic flexure of the colon, duodenum, gallbladder, inferior vena cava, and esophagus and fundus of the stomach

Peritoneal Ligaments of the Liver The falciform ligament, which is a two-layered fold of the peritoneum, ascends from the umbilicus to the liver (Fig. 5-8). It has a sickle-shaped free margin that contains the ligamentum teres, the remains of the umbilical vein. The falciform ligament passes on to the anterior and then the P.249
superior surfaces of the liver and then splits into two layers. The right layer forms the upper layer of the coronary ligament; the left layer forms the upper layer of the left triangular ligament (Fig. 5-8). The right extremity of the coronary ligament is known as the right triangular ligament of the liver. It should be noted that the peritoneal layers forming the coronary ligament are widely separated, leaving an area of liver devoid of peritoneum. Such an area is referred to as a bare area of the liver (Fig. 5-8). The ligamentum teres passes into a fissure on the visceral surface of the liver and joins the left branch of the portal vein in the porta hepatis (Figs. 5-9 and 5-22). The ligamentum venosum, a fibrous band that is the remains of the ductus venosus, is attached to the left branch of the portal vein and ascends in a fissure on the visceral surface of the liver to be attached above to the inferior vena cava (Figs. 5-8 and 5-22). In the fetus, oxygenated blood is brought to the liver in the umbilical vein (ligamentum teres). The greater proportion of the blood bypasses the liver in the ductus venosus (ligamentum venosum) and joins the inferior vena cava. At birth, the umbilical vein and ductus venosus close and become fibrous cords. The lesser omentum arises from the edges of the porta hepatis and the fissure for the ligamentum venosum and passes down to the lesser curvature of the stomach (Fig. 5-10). Blood Supply Arteries The hepatic artery, a branch of the celiac artery, divides into right and left terminal branches that enter the porta hepatis. Clinical Notes Liver Supports and Surgery The liver is held in position in the upper part of the abdominal cavity by the attachment of the hepatic veins to the inferior vena cava. The peritoneal ligaments and the tone of the abdominal muscles play a minor role in its support. This fact is important surgically because even if the peritoneal ligaments are cut, the liver can be only slightly rotated. Liver Trauma The liver is a soft, friable structure enclosed in a fibrous capsule. Its close relationship to the lower ribs must be emphasized. Fractures of the lower ribs or penetrating wounds of the thorax or upper abdomen are common causes of liver injury. Blunt traumatic injuries from automobile accidents are also common, and severe hemorrhage accompanies tears of this organ. Because anatomic research has shown that the bile ducts, hepatic arteries, and portal vein are distributed in a segmental manner, appropriate ligation of these structures allows the surgeon to remove large portions of the liver in patients with severe traumatic lacerations of the liver or with a liver tumor. (Even large, localized carcinomatous metastatic tumors have been successfully removed.) Liver Biopsy Liver biopsy is a common diagnostic procedure. With the patient holding his or her breath in full expiration—to reduce the size of the costodiaphragmatic recess and the likelihood of damage to the lung—a needle is inserted through the right eighth or ninth intercostal space in the midaxillary line. The needle passes through the diaphragm into the liver, and a small specimen of liver tissue is removed for microscopic examination. Subphrenic Spaces The important subphrenic spaces and their relationship to the liver are described on page 208. Under normal conditions these are potential spaces only, and the peritoneal surfaces are in contact. An abnormal accumulation of gas or fluid is necessary for separation of the peritoneal surfaces. The anterior surface of the liver is normally dull on percussion. Perforation of a gastric ulcer is often accompanied by a loss of liver dullness caused by the accumulation of gas over the anterior surface of the liver and in the subphrenic spaces. Veins The portal vein divides into right and left terminal branches that enter the porta hepatis behind the arteries. The hepatic veins (three or more) emerge from the posterior surface of the liver and drain into the inferior vena cava. Blood Circulation through the Liver The blood vessels (Fig. 5-47) conveying blood to the liver are the hepatic artery (30%) and portal vein (70%). The hepatic artery brings oxygenated blood to the liver, and the portal vein brings venous blood rich in the products of digestion, which have been absorbed from the gastrointestinal tract. The arterial and venous blood is conducted to the central vein of each liver lobule by the liver sinusoids. The central veins drain into the right and left hepatic veins, and these leave the posterior surface of the liver and open directly into the inferior vena cava. Lymph Drainage The liver produces a large amount of lymph—about one third to one half of all body lymph. The lymph vessels leave the liver and enter several lymph nodes in the porta hepatis. The efferent vessels pass to the celiac nodes. A few vessels pass from the bare area of the liver through the diaphragm to the posterior mediastinal lymph nodes. Nerve Supply Sympathetic and parasympathetic nerves form the celiac plexus. The anterior vagal trunk gives rise to a large hepatic branch, which passes directly to the liver. P.250
Bile Ducts of the Liver Bile is secreted by the liver cells at a constant rate of about 40 mL per hour. When digestion is not taking place, the bile is stored and concentrated in the gallbladder; later, it is delivered to the duodenum. The bile ducts of the liver consist of the right and left hepatic ducts, the common hepatic duct, the bile duct, the gallbladder, and the cystic duct. The smallest interlobular tributaries of the bile ducts are situated in the portal canals of the liver; they receive the bile canaliculi. The interlobular ducts join one another to form progressively larger ducts and, eventually, at the porta hepatis, form the right and left hepatic ducts. The right hepatic duct drains the right lobe of the liver and the left duct drains the left lobe, caudate lobe, and quadrate lobe. Hepatic Ducts The right and left hepatic ducts emerge from the right and left lobes of the liver in the porta hepatis (Fig. 5-47). After a short course, the hepatic ducts unite to form the common hepatic duct (Fig. 5-29). The common hepatic duct is about 1.5 in. (4 cm) long and descends within the free margin of the lesser omentum. It is joined on the right side by the cystic duct from the gallbladder to form the bile duct (Fig. 5-29). Bile Duct The bile duct (common bile duct) is about 3 in. (8 cm) long. In the first part of its course, it lies in the right free margin of the lesser omentum in front of the opening into the lesser sac. Here, it lies in front of the right margin of the portal vein and on the right of the hepatic artery (Fig. 5-11). In the second part of its course, it is situated behind the first part of the duodenum (Fig. 5-7) to the right of the gastroduodenal artery (Fig. 5-4). In the third part of its course, it lies in a groove on the posterior surface of the head of the pancreas (Fig. 5-29). Here, the bile duct comes into contact with the main pancreatic duct.

Figure 5-51 Terminal parts of the bile and pancreatic ducts as they enter the second part of the duodenum. Note the sphincter of Oddi and the smooth muscle around the ends of the bile duct and the main pancreatic duct.

The bile duct ends below by piercing the medial wall of the second part of the duodenum about halfway down its length (Fig. 5-51). It is usually joined by the main pancreatic duct, and together they open into a small ampulla in the duodenal wall, called the hepatopancreatic ampulla (ampulla of Vater). The ampulla opens into the lumen of the duodenum by means of a small papilla, the major duodenal papilla (Fig. 5-51). The terminal parts of both ducts and the ampulla are surrounded by circular muscle, known as the sphincter of the hepatopancreatic ampulla (sphincter of Oddi) (Fig. 5-51). Occasionally, the bile and pancreatic ducts open separately into the duodenum. The common variations of this arrangement are shown in Figure 5-52. Gallbladder Location and Description The gallbladder is a pear-shaped sac lying on the undersurface of the liver (Figs. 5-8, 5-9, and 5-29). It has a capacity of 30 to 50 mL and stores bile, which it concentrates by absorbing water. The gallbladder is divided into the fundus, body, and neck. The fundus is rounded and projects below the inferior margin of the liver, where it comes in contact with the anterior abdominal wall at the level of the tip of the ninth right costal cartilage. The body lies in contact P.251
with the visceral surface of the liver and is directed upward, backward, and to the left. The neck becomes continuous with the cystic duct, which turns into the lesser omentum to join the common hepatic duct, to form the bile duct (Fig. 5-29).

Figure 5-52 Three common variations of terminations of the bile and main pancreatic ducts as they enter the second part of the duodenum.

The peritoneum completely surrounds the fundus of the gallbladder and binds the body and neck to the visceral surface of the liver. Relations

  • Anteriorly: The anterior abdominal wall and the inferior surface of the liver (Fig. 5-2)
  • Posteriorly: The transverse colon and the first and second parts of the duodenum (Fig. 5-29)

Function of the Gallbladder When digestion is not taking place, the sphincter of Oddi remains closed and bile accumulates in the gallbladder. The gallbladder concentrates bile; stores bile; selectively absorbs bile salts, keeping the bile acid; excretes cholesterol; and secretes mucus. To aid in these functions, the mucous membrane is thrown into permanent folds that unite with each other, giving the surface a honeycombed appearance. The columnar cells lining the surface have numerous microvilli on their free surface. Bile is delivered to the duodenum as the result of contraction and partial emptying of the gallbladder. This mechanism is initiated by the entrance of fatty foods into the duodenum. The fat causes release of the hormone cholecystokinin from the mucous membrane of the duodenum; the hormone then enters the blood, causing the gallbladder to contract. At the same time, the smooth muscle around the distal end of the bile duct and the ampulla is relaxed, thus allowing the passage of concentrated bile into the duodenum. The bile salts in the bile are important in emulsifying the fat in the intestine and in assisting with its digestion and absorption. Blood Supply The cystic artery, a branch of the right hepatic artery (Fig. 5-47), supplies the gallbladder. The cystic vein drains directly into the portal vein. Several very small arteries and veins also run between the liver and gallbladder. Lymph Drainage The lymph drains into a cystic lymph node situated near the neck of the gallbladder. From here, the lymph vessels pass to the hepatic nodes along the course of the hepatic artery and then to the celiac nodes. Nerve Supply Sympathetic and parasympathetic vagal fibers form the celiac plexus. The gallbladder contracts in response to the hormone cholecystokinin, which is produced by the mucous membrane of the duodenum on the arrival of fatty food from the stomach. Clinical Notes Gallstones Gallstones are usually asymptomatic; however, they can give rise to gallstone colic or produce acute cholecystitis. Biliary Colic Biliary colic is usually caused by spasm of the smooth muscle of the wall of the gallbladder in an attempt to expel a gallstone. Afferent nerve fibers ascend through the celiac plexus and the greater splanchnic nerves to the thoracic segments of the spinal cord. Referred pain is felt in the right upper quadrant or the epigastrium (T7, 8, and 9 dermatomes). Obstruction of the biliary ducts with a gallstone or by compression by a tumor of the pancreas results in backup of bile in the ducts and development of jaundice. The impaction of a stone in the ampulla of Vater may result in the passage of infected bile into the pancreatic duct, producing pancreatitis. The anatomic arrangement of the terminal part of the bile duct and the main pancreatic duct is subject to considerable variation. The type of duct system present determines whether infected bile is likely to enter the pancreatic duct. Gallstones have been known to ulcerate through the gallbladder wall into the transverse colon or the duodenum. In the former case, they are passed naturally per the rectum, but in the latter case, they may be held up at the ileocecal junction, producing intestinal obstruction. Acute Cholecystitis Acute cholecystitis produces discomfort in the right upper quadrant or epigastrium. Inflammation of the gallbladder may cause irritation of the subdiaphragmatic parietal peritoneum, which is supplied in part by the phrenic nerve (C3, 4, and 5). This may give rise to referred pain over the shoulder, because the skin in this area is supplied by the supraclavicular nerves (C3 and 4). Cholecystectomy and the Arterial Supply to the Gallbladder Before attempting a cholecystectomy operation, the surgeon must be aware of the many variations in the arterial supply to the gallbladder and the relationship of the vessels to the bile ducts (Fig. 5-53). Unfortunately, there have been several reported cases in which the common hepatic duct or the main bile duct have been included in the arterial ligature with disastrous consequences. Gangrene of the Gallbladder Unlike the appendix, which has a single arterial supply, the gallbladder rarely becomes gangrenous. In addition to the cystic artery, the gallbladder also receives small vessels from the visceral surface of the liver. Sonograms can now be used to demonstrate the gallbladder (Fig. 5-54). P.252

Figure 5-53 Some common variations of blood supply to the gallbladder.
Figure 5-54 Longitudinal sonogram of the upper part of the abdomen showing the lumen of the gallbladder. (Courtesy of Dr. M.C. Hill.)

P.253
Cystic Duct The cystic duct is about 1.5 in. (3.8 cm) long and connects the neck of the gallbladder to the common hepatic duct to form the bile duct (Fig. 5-29). It usually is somewhat S-shaped and descends for a variable distance in the right free margin of the lesser omentum. The mucous membrane of the cystic duct is raised to form a spiral fold that is continuous with a similar fold in the neck of the gallbladder. The fold is commonly known as the “spiral valve.” The function of the spiral valve is to keep the lumen constantly open. Embryologic Notes Development of the Liver and Bile Ducts Liver The liver arises from the distal end of the foregut as a solid bud of entodermal cells (Figs. 5-41 and 5-55). The site of origin lies at the apex of the loop of the developing duodenum and corresponds to a point halfway along the second part of the fully formed duodenum. The hepatic bud grows anteriorly into the mass of splanchnic mesoderm called the septum transversum. The end of the bud now divides into right and left branches, from which columns of entodermal cells grow into the vascular mesoderm. The paired vitelline veins and umbilical veins that course through the septum transversum become broken up by the invading columns of liver cells and form the liver sinusoids. The columns of entodermal cells form the liver cords. The connective tissue of the liver is formed from the mesenchyme of the septum transversum. The main hepatic bud and its right and left terminal branches now become canalized to form the common hepatic duct and the right and left hepatic ducts. The liver grows rapidly in size and comes to occupy the greater part of the abdominal cavity; the right lobe becomes much larger than the left lobe. Gallbladder and Cystic Duct The gallbladder develops from the hepatic bud as a solid outgrowth of cells (Fig. 5-41). The end of the outgrowth expands to form the gallbladder, while the narrow stem remains as the cystic duct. Later, the gallbladder and cystic duct become canalized. The cystic duct now opens into the common hepatic duct to form the bile duct. Biliary Atresia Failure of the bile ducts to canalize during development causes atresia. The various forms of atresia are shown in Figure 5-56. Jaundice appears soon after birth; clay-colored stools and very dark colored urine are also present. Surgical correction of the atresia should be attempted when possible. If the atresia cannot be corrected, the child will die of liver failure. Absence of the Gallbladder Occasionally, the outgrowth of cells from the hepatic bud fails to develop. In these cases, there is no gallbladder and no cystic duct (Fig. 5-57).

Figure 5-55 Development of the duodenum in relation to the ventral and dorsal mesenteries. Stippled area, foregut; crosshatched area, midgut.

Double Gallbladder Rarely, the outgrowth of cells from the hepatic bud bifurcates so that two gallbladders are formed (Fig. 5-57). Absence of the Cystic Duct In absence of the cystic duct, the entire outgrowth of cells from the hepatic bud develops into the gallbladder and fails to leave the narrow stem that would normally form the cystic duct. The gallbladder drains directly into the bile duct. The condition may not be recognized when performing a cholecystectomy, and the bile duct may be seriously damaged by the surgeon (Fig. 5-57). Accessory Bile Duct A small accessory bile duct may open directly from the liver into the gallbladder, which may cause leakage of bile into the peritoneal cavity after cholecystectomy if it is not recognized at the time of surgery (Fig. 5-57). Congenital Choledochal Cyst Rarely, a choledochal cyst develops because of an area of weakness in the wall of the bile duct. A cyst can contain 1 to 2 L of bile. The anomaly is important in that it may press on the bile duct and cause obstructive jaundice (Fig. 5-57). P.254
P.255

Figure 5-56 Some common congenital anomalies of the biliary ducts.
Figure 5-57 Some common congenital anomalies of the gallbladder.

P.256
Pancreas Location and Description The pancreas is both an exocrine and an endocrine gland. The exocrine portion of the gland produces a secretion that contains enzymes capable of hydrolyzing proteins, fats, and carbohydrates. The endocrine portion of the gland, the pancreatic islets (islets of Langerhans), produces the hormones insulin and glucagon, which play a key role in carbohydrate metabolism. The pancreas is an elongated structure that lies in the epigastrium and the left upper quadrant. It is soft and lobulated and situated on the posterior abdominal wall behind the peritoneum. It crosses the transpyloric plane. The pancreas is divided into a head, neck, body, and tail (Fig. 5-58). The head of the pancreas is disc shaped and lies within the concavity of the duodenum (Fig. 5-58). A part of the head extends to the left behind the superior mesenteric vessels and is called the uncinate process. The neck is the constricted portion of the pancreas and connects the head to the body. It lies in front of the beginning of the portal vein and the origin of the superior mesenteric artery from the aorta (Fig. 5-26).

Figure 5-58 Different parts of the pancreas dissected to reveal the duct system.

The body runs upward and to the left across the midline (Fig. 5-4). It is somewhat triangular in cross section. The tail passes forward in the splenicorenal ligament and comes in contact with the hilum of the spleen (Fig. 5-4). Relations

  • Anteriorly: From right to left: the transverse colon and the attachment of the transverse mesocolon, the lesser sac, and the stomach (Figs. 5-4 and 5-6)
  • Posteriorly: From right to left: the bile duct, the portal and splenic veins, the inferior vena cava, the aorta, the origin of the superior mesenteric artery, the left psoas muscle, the left suprarenal gland, the left kidney, and the hilum of the spleen (Figs. 5-4 and 5-27)

Pancreatic Ducts The main duct of the pancreas begins in the tail and runs the length of the gland, receiving numerous tributaries on the way (Fig. 5-58). It opens into the second part of the duodenum at about its middle with the bile duct on the major duodenal papilla (Fig. 5-51). Sometimes the main duct drains separately into the duodenum. P.257
The accessory duct of the pancreas, when present, drains the upper part of the head and then opens into the duodenum a short distance above the main duct on the minor duodenal papilla (Figs. 5-51 and 5-58). The accessory duct frequently communicates with the main duct. Blood Supply Arteries The splenic and the superior and inferior pancreaticoduodenal arteries (Fig. 5-26) supply the pancreas. Veins The corresponding veins drain into the portal system. Lymph Drainage Lymph nodes are situated along the arteries that supply the gland. The efferent vessels ultimately drain into the celiac and superior mesenteric lymph nodes. Nerve Supply Sympathetic and parasympathetic (vagal) nerve fibers supply the area. Clinical Notes Diagnosis of Pancreatic Disease The deep location of the pancreas sometimes gives rise to problems of diagnosis for the following reasons:

  • Pain from the pancreas is commonly referred to the back.
  • Because the pancreas lies behind the stomach and transverse colon, disease of the gland can be confused with that of the stomach or transverse colon.
  • Inflammation of the pancreas can spread to the peritoneum forming the posterior wall of the lesser sac. This in turn can lead to adhesions and the closing off of the lesser sac to form a pseudocyst.

Trauma of the Pancreas The pancreas is deeply placed within the abdomen and is well protected by the costal margin and the anterior abdominal wall. However, blunt trauma, such as in a sports injury when a sudden blow to the abdomen occurs, can compress and tear the pancreas against the vertebral column. The pancreas is most commonly damaged by gunshot or stab wounds. Damaged pancreatic tissue releases activated pancreatic enzymes that produce the signs and symptoms of acute peritonitis. Cancer of the Head of the Pancreas and the Bile Duct Because of the close relation of the head of the pancreas to the bile duct, cancer of the head of the pancreas often causes obstructive jaundice. The Pancreatic Tail and Splenectomy The presence of the tail of the pancreas in the splenicorenal ligament sometimes results in its damage during splenectomy. The damaged pancreas releases enzymes that start to digest surrounding tissues, with serious consequences. P.258
Embryologic Notes Development of the Pancreas The pancreas develops from a dorsal and ventral bud of entodermal cells that arise from the foregut. The dorsal bud originates a short distance above the ventral bud and grows into the dorsal mesentery. The ventral bud arises in common with the hepatic bud, close to the junction of the foregut with the midgut (Fig. 5-41). A canalized duct system now develops in each bud. The rotation of the stomach and duodenum, together with the rapid growth of the left side of the duodenum, results in the ventral bud’s coming into contact with the dorsal bud, and fusion occurs (Fig. 5-59). Fusion also occurs between the ducts, so that the main pancreatic duct is derived from the entire ventral pancreatic duct and the distal part of the dorsal pancreatic duct. The main pancreatic duct joins the bile duct and enters the second part of the duodenum. The proximal part of the dorsal pancreatic duct may persist as an accessory duct, which may or may not open into the duodenum about 0.75 in. (2 cm) above the opening of the main duct. Continued growth of the entodermal cells of the now-fused ventral and dorsal pancreatic buds extends into the surrounding mesenchyme as columns of cells. These columns give off side branches, which later become canalized to form collecting ducts. Secretory acini appear at the ends of the ducts. The pancreatic islets arise as small buds from the developing ducts. Later, these cells sever their connection with the duct system and form isolated groups of cells that start to secrete insulin and glucagon at about the fifth month. The inferior part of the head and the uncinate process of the pancreas are formed from the ventral pancreatic bud; the superior part of the head, the neck, the body, and the tail of the pancreas are formed from the dorsal pancreatic bud (Fig. 5-59).

Figure 5-59 The rotation of the duodenum and the unequal growth of the duodenal wall lead to the fusing of the ventral and dorsal pancreatic buds.

Entrance of the Bile Duct and Pancreatic Duct into the Duodenum As seen from development, the bile duct and the main pancreatic duct are joined to one another. They pass obliquely through the wall of the second part of the duodenum to open on the summit of the major duodenal papilla, which is surrounded by the sphincter of Oddi (Fig. 5-52). In some individuals, they pass separately through the duodenal wall, although in close contact, and open separately on the summit of the duodenal papilla. In other individuals, the two ducts join and form a common dilatation, the hepatopancreatic ampulla (ampulla of Vater). This opens on the summit of the duodenal papilla. Anular Pancreas In anular pancreas, the ventral pancreatic bud becomes fixed so that, when the stomach and duodenum rotate, the ventral bud is pulled around the right side of the duodenum to fuse with the dorsal bud of the pancreas, thus encircling the duodenum (Fig. 5-60). This may cause obstruction of the duodenum, and vomiting may start a few hours after birth. Early surgical relief of the obstruction is necessary. Ectopic Pancreas Ectopic pancreatic tissue may be found in the submucosa of the stomach, duodenum, small intestine (including Meckel’s diverticulum), and gallbladder, and in the spleen. It is important in that it may protrude into the lumen of the gut and be responsible for causing intussusception. Congenital Fibrocystic Disease Basically, congenital fibrocystic disease in the pancreas is caused by an abnormality in the secretion of mucus. The mucus produced is excessively viscid and obstructs the pancreatic duct, which leads to pancreatitis with subsequent fibrosis. The condition also involves the lungs, kidneys, and liver.

Figure 5-60 Formation of the anular pancreas, producing duodenal obstruction. Note the narrowing of the duodenum.

P.259
Spleen Location and Description The spleen is reddish and is the largest single mass of lymphoid tissue in the body. It is oval shaped and has a notched anterior border. It lies just beneath the left half of the diaphragm close to the 9th, 10th, and 11th ribs. The long axis lies along the shaft of the 10th rib, and its lower pole extends forward only as far as the midaxillary line and cannot be palpated on clinical examination (Fig. 5-61). The spleen is surrounded by peritoneum (Figs. 5-5 and 5-61), which passes from it at the hilum as the gastrosplenic omentum (ligament) to the greater curvature of the stomach (carrying the short gastric and left gastroepiploic vessels). The peritoneum also passes to the left kidney as the splenicorenal ligament (carrying the splenic vessels and the tail of the pancreas). Relations

  • Anteriorly: The stomach, tail of the pancreas, and left colic flexure. The left kidney lies along its medial border (Figs. 5-4 and 5-11).
    Figure 5-61 Spleen, with its notched anterior border, and its relation to adjacent structures.
  • Posteriorly: The diaphragm; left pleura (left costodiaphragmatic recess); left lung; and 9th, 10th, and 11th ribs (Figs. 5-11 and 5-61)

Blood Supply Arteries The large splenic artery is the largest branch of the celiac artery. It has a tortuous course as it runs along the upper border of the pancreas. The splenic artery then divides into about six branches, which enter the spleen at the hilum. Veins The splenic vein leaves the hilum and runs behind the tail and the body of the pancreas. Behind the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein. Lymph Drainage The lymph vessels emerge from the hilum and pass through a few lymph nodes along the course of the splenic artery and then drain into the celiac nodes. Nerve Supply The nerves accompany the splenic artery and are derived from the celiac plexus. Clinical Notes Splenic Enlargement A pathologically enlarged spleen extends downward and medially. The left colic flexure and the phrenicocolic ligament prevent a direct downward enlargement of the organ. As the enlarged spleen projects below the left costal margin, its notched anterior border can be recognized by palpation through the anterior abdominal wall. The spleen is situated at the beginning of the splenic vein, and in cases of portal hypertension it often enlarges from venous congestion. Trauma to the Spleen Although anatomically the spleen gives the appearance of being well protected, automobile accidents of the crushing or run-over type commonly produce laceration of the spleen. Penetrating wounds of the lower left thorax can also damage the spleen. P.260
Embryologic Notes Development of the Spleen The spleen develops as a thickening of the mesenchyme in the dorsal mesentery (Fig. 5-46). In the earliest stages, the spleen consists of a number of mesenchymal masses that later fuse. The notches along its anterior border are permanent and indicate that the mesenchymal masses never completely fuse. The part of the dorsal mesentery that extends between the hilum of the spleen and the greater curvature of the stomach is called the gastrosplenic omentum; the part that extends between the spleen and the left kidney on the posterior abdominal wall is called the splenicorenal ligament. The spleen is supplied by a branch of the foregut artery (celiac artery), the splenic artery. Supernumerary Spleen In 10% of people, one or more supernumerary spleens may be present, either in the gastrosplenic omentum or in the splenicorenal ligament. Their clinical importance is that they may hypertrophy after removal of the major spleen and be responsible for a recurrence of symptoms of the disease for which splenectomy was initially performed. Retroperitoneal Space The retroperitoneal space lies on the posterior abdominal wall behind the parietal peritoneum. It extends from the 12th thoracic vertebra and the 12th rib to the sacrum and the iliac crests below (Fig. 5-62). The floor or posterior wall of the space is formed from medial to lateral by the psoas and quadratus lumborum muscles and the origin of the transversus abdominis muscle. Each of these muscles is covered on the anterior surface by a definite layer of fascia. In front of the fascial layers is a variable amount of fatty connective tissue that forms a bed for the suprarenal glands, the kidneys, the ascending and descending parts of the colon, and the duodenum. The retroperitoneal space also contains the ureters and the renal and gonadal blood vessels. Clinical Notes Trauma to Organs in the Retroperitoneal Space Palpation of the anterior abdominal wall in the lumbar and iliac regions may give rise to signs indicative of peritoneal irritation (the peritoneum forms the anterior boundary of the space; Fig. 5-62). In other words, tenderness and muscle spasm (rigidity) may be present. Palpation of the back in the interval between the 12th rib and the vertebral column may reveal tenderness suggestive of kidney disease. Abdominal radiographs may reveal air in the extraperitoneal tissues, indicating perforation of a viscus (e.g., ascending or descending colon). Computed tomography scans can often accurately define the extent of the injury to the extraperitoneal organs. Abscess Formation Infection originating in retroperitoneal organs, such as the kidneys, lymph nodes, and retrocecal appendix, may extend widely into the retroperitoneal space. Leaking Aortic Aneurysm The blood may first be confined to the retroperitoneal space before rupturing into the peritoneal cavity. Urinary Tract Kidneys Location and Description The two kidneys function to excrete most of the waste products of metabolism. They play a major role in controlling the water and electrolyte balance within the body and in maintaining the acid–base balance of the blood. The waste products leave the kidneys as urine, which passes down the ureters to the urinary bladder, located within the pelvis. The urine leaves the body in the urethra. The kidneys are reddish brown and lie behind the peritoneum high up on the posterior abdominal wall on either side of the vertebral column; they are largely under cover of the costal margin (Fig. 5-63). The right kidney lies slightly lower than the left kidney because of the large size of the right lobe of the liver. With contraction of the diaphragm during respiration, both kidneys move downward in a vertical direction by as much as 1 in. (2.5 cm). On the medial concave border of each kidney is a vertical slit that is bounded by thick lips of renal substance and is called the hilum (Fig. 5-64). The hilum extends into a large cavity called the renal sinus. The hilum transmits, from the front backward, the renal vein, two branches of the renal artery, the ureter, and the third branch of the renal artery (VAUA). Lymph vessels and sympathetic fibers also pass through the hilum. P.261

Figure 5-62 Retroperitoneal space. A. Structures present on the posterior abdominal wall behind the peritoneum. B. Transverse section of the posterior abdominal wall showing structures in the retroperitoneal space as seen from below.

P.262

Figure 5-63 Posterior abdominal wall showing the kidneys and the ureters in situ. Arrows indicate three sites where the ureter is narrowed.

Coverings The kidneys have the following coverings (Fig. 5-64):

  • Fibrous capsule: This surrounds the kidney and is closely applied to its outer surface.
  • Perirenal fat: This covers the fibrous capsule.
  • Renal fascia: This is a condensation of connective tissue that lies outside the perirenal fat and encloses the kidneys and suprarenal glands; it is continuous laterally with the fascia transversalis.
  • Pararenal fat: This lies external to the renal fascia and is often in large quantity. It forms part of the retroperitoneal fat.

The perirenal fat, renal fascia, and pararenal fat support the kidneys and hold them in position on the posterior abdominal wall. Renal Structure Each kidney has a dark brown outer cortex and a light brown inner medulla. The medulla is composed of about a dozen renal pyramids, each having its base oriented toward the cortex and its apex, the renal papilla, projecting medially (Fig. 5-64). The cortex extends into the medulla between adjacent pyramids as the renal columns. Extending from the bases of the renal pyramids into the cortex are striations known as medullary rays. The renal sinus, which is the space within the hilum, contains the upper expanded end of the ureter, the renal pelvis. This divides into two or three major calyces, each of which divides into two or three minor calyces (Fig. 5-64). Each minor calyx is indented by the apex of the renal pyramid, the renal papilla. Important Relations, Right Kidney

  • Anteriorly: The suprarenal gland, the liver, the second part of the duodenum, and the right colic flexure (Figs. 5-4 and 5-65)
  • Posteriorly: The diaphragm; the costodiaphragmatic recess of the pleura; the 12th rib; and the psoas, quadratus lumborum, and transversus abdominis muscles. The subcostal (T12), iliohypogastric, and ilioinguinal nerves (L1) run downward and laterally (Fig. 5-34).

P.263

Figure 5-64 A. Right kidney, anterior surface. B. Right kidney, coronal section showing the cortex, medulla, pyramids, renal papillae, and calyces. C. Section of the kidney showing the position of the nephrons and the arrangement of the blood vessels within the kidney.

P.264
Important Relations, Left Kidney

  • Anteriorly: The suprarenal gland, the spleen, the stomach, the pancreas, the left colic flexure, and coils of jejunum (Figs. 5-4 and 5-65)
  • Posteriorly: The diaphragm; the costodiaphragmatic recess of the pleura; the 11th (the left kidney is higher) and 12th ribs; and the psoas, quadratus lumborum, and transversus abdominis muscles. The subcostal (T12), iliohypogastric, and ilioinguinal nerves (L1) run downward and laterally (Fig. 5-34).

Note that many of the structures are directly in contact with the kidneys, whereas others are separated by visceral layers of peritoneum. For details, see Figure 5-65. Blood Supply Arteries The renal artery arises from the aorta at the level of the second lumbar vertebra. Each renal artery usually divides into five segmental arteries that enter the hilum of the kidney. They are distributed to different segments or areas of the kidney. Lobar arteries arise from each segmental artery, one for each renal pyramid. Before entering the renal substance, each lobar artery gives off two or three interlobar arteries (Fig. 5-64). The interlobar arteries run toward the cortex on each side of the renal pyramid. At the junction of the cortex and the medulla, the interlobar arteries give off the arcuate arteries, which arch over the bases of the pyramids (Fig. 5-65). The arcuate arteries give off several interlobular arteries that ascend in the cortex. The afferent glomerular arterioles arise as branches of the interlobular arteries. Clinical Notes Renal Mobility The kidneys are maintained in their normal position by intra-abdominal pressure and by their connections with the perirenal fat and renal fascia. Each kidney moves slightly with respiration. The right kidney lies at a slightly lower level than the left kidney, and the lower pole may be palpated in the right lumbar region at the end of deep inspiration in a person with poorly developed abdominal musculature. Should the amount of perirenal fat be reduced, the mobility of the kidney may become excessive and produce symptoms of renal colic caused by kinking of the ureter. Excessive mobility of the kidney leaves the suprarenal gland undisturbed because the latter occupies a separate compartment in the renal fascia. Kidney Trauma The kidneys are well protected by the lower ribs, the lumbar muscles, and the vertebral column. However, a severe blunt injury applied to the abdomen may crush the kidney against the last rib and the vertebral column. Depending on the severity of the blow, the injury varies from a mild bruising to a complete laceration of the organ. Penetrating injuries are usually caused by stab wounds or gunshot wounds and often involve other viscera. Because 25% of the cardiac outflow passes through the kidneys, renal injury can result in rapid blood loss. A summary of the injuries to the kidneys is shown in Figure 5-66. Kidney Tumors Malignant tumors of the kidney have a strong tendency to spread along the renal vein. The left renal vein receives the left testicular vein in the male, and this may rarely become blocked, producing left-sided varicocele (see page 169). Renal Pain Renal pain varies from a dull ache to a severe pain in the flank that may radiate downward into the lower abdomen. Renal pain can result from stretching of the kidney capsule or spasm of the smooth muscle in the renal pelvis. The afferent nerve fibers pass through the renal plexus around the renal artery and ascend to the spinal cord through the lowest splanchnic nerve in the thorax and the sympathetic trunk. They enter the spinal cord at the level of T12. Pain is commonly referred along the distribution of the subcostal nerve (T12) to the flank and the anterior abdominal wall. Transplanted Kidneys The iliac fossa on the posterior abdominal wall is the usual site chosen for transplantation of the kidney. The fossa is exposed through an incision in the anterior abdominal wall just above the inguinal ligament. The iliac fossa in front of the iliacus muscle is approached retroperitoneally. The kidney is positioned and the vascular anastomosis constructed. The renal artery is anastomosed end-to-end to the internal iliac artery and the renal vein is anastomosed end-to-side to the external iliac vein (Fig. 5-67). Anastomosis of the branches of the internal iliac arteries on the two sides is sufficient so that the pelvic viscera on the side of the renal arterial anastomosis are not at risk. Ureterocystostomy is then performed by opening the bladder and providing a wide entrance of the ureter through the bladder wall. Veins The renal vein emerges from the hilum in front of the renal artery and drains into the inferior vena cava. Lymph Drainage Lymph drains to the lateral aortic lymph nodes around the origin of the renal artery. Nerve Supply The nerve supply is the renal sympathetic plexus. The afferent fibers that travel through the renal plexus enter the spinal cord in the 10th, 11th, and 12th thoracic nerves. P.265

Figure 5-65 Anterior relations of both kidneys. Visceral peritoneum covering the kidneys has been left in position. Brown areas indicate where the kidney is in direct contact with the adjacent viscera.
Figure 5-66 Injuries to the kidney. A. Contusion, with hemorrhage confined to the cortex beneath the intact fibrous capsule. B. Tearing of the capsule and cortex with bleeding occurring into the perirenal fat. C. Tearing of the capsule, the cortex, and the medulla. Note the escape of blood into the calyces and therefore the urine. Urine as well as blood may extravasate into the perirenal and pararenal fat and into the peritoneal cavity. D. Shattered kidney with extensive hemorrhage and extravasation of blood and urine into the perirenal and pararenal fat; blood also enters the calyces and appears in the urine. E. Injury to the renal pedicle involving the renal vessels and possibly the renal pelvis.

P.266

Figure 5-67 The transplanted kidney.

Ureter Location and Description The two ureters are muscular tubes that extend from the kidneys to the posterior surface of the urinary bladder (Fig. 5-63). The urine is propelled along the ureter by peristaltic contractions of the muscle coat, assisted by the filtration pressure of the glomeruli. Each ureter measures about 10 in. (25 cm) long and resembles the esophagus (also 10 in. long) in having three constrictions along its course: where the renal pelvis joins the ureter, where it is kinked as it crosses the pelvic brim, and where it pierces the bladder wall (Fig. 5-63). The renal pelvis is the funnel-shaped expanded upper end of the ureter. It lies within the hilum of the kidney and receives the major calyces (Fig. 5-64). The ureter emerges from the hilum of the kidney and runs vertically downward behind the parietal peritoneum (adherent to it) on the psoas muscle, which separates it from the tips of the transverse processes of the lumbar vertebrae. It enters the pelvis by crossing the bifurcation of the common iliac artery in front of the sacroiliac joint (Fig. 5-63). The ureter then runs down the lateral wall of the pelvis to the region of the ischial spine and turns forward to enter the lateral angle of the bladder. The pelvic course of the ureter is described in detail on pages 347 and 355. Relations, Right Ureter

  • Anteriorly: The duodenum, the terminal part of the ileum, the right colic and ileocolic vessels, the right testicular or ovarian vessels, and the root of the mesentery of the small intestine (Fig. 5-27)
  • Posteriorly: The right psoas muscle, which separates it from the lumbar transverse processes, and the bifurcation of the right common iliac artery (Fig. 5-63)

Relations, Left Ureter

  • Anteriorly: The sigmoid colon and sigmoid mesocolon, the left colic vessels, and the left testicular or ovarian vessels (Figs. 5-13 and 5-27)
  • Posteriorly: The left psoas muscle, which separates it from the lumbar transverse processes, and the bifurcation of the left common iliac artery (Fig. 5-63)

The inferior mesenteric vein lies along the medial side of the left ureter (Fig. 5-27). Blood Supply Arteries The arterial supply to the ureter is as follows: upper end, the renal artery; middle portion, the testicular or ovarian artery; and in the pelvis, the superior vesical artery. Veins Venous blood drains into veins that correspond to the arteries. Lymph Drainage The lymph drains to the lateral aortic nodes and the iliac nodes. Nerve Supply The nerve supply is the renal, testicular (or ovarian), and hypogastric plexuses (in the pelvis). Afferent fibers travel with the sympathetic nerves and enter the spinal cord in the first and second lumbar segments. Clinical Notes Traumatic Ureteral Injuries Because of its protected position and small size, injuries to the ureter are rare. Most injuries are caused by gunshot wounds and, in a few individuals, penetrating stab wounds. Because the ureters are retroperitoneal in position, urine may escape into the retroperitoneal tissues on the posterior abdominal wall. Ureteric Stones There are three sites of anatomic narrowing of the ureter where stones may be arrested, namely, the pelviureteral junction, the pelvic brim, and where the ureter enters the bladder. Most stones, although radiopaque, are small enough to be impossible to see definitely along the course of the ureter on plain radiographic examination. An intravenous pyelogram is usually necessary. The ureter runs down in front of the tips of the transverse processes of the lumbar vertebrae, crosses the region of the sacroiliac joint, swings out to the ischial spine, and then turns medially to the bladder. Renal Colic The renal pelvis and the ureter send their afferent nerves into the spinal cord at segments T11 and 12 and L1 and 2. In renal colic, strong peristaltic waves of contraction pass down the ureter in an attempt to pass the stone onward. The spasm of the smooth muscle causes an agonizing colicky pain, which is referred to the skin areas that are supplied by these segments of the spinal cord, namely, the flank, loin, and groin. When a stone enters the low part of the ureter, the pain is felt at a lower level and is often referred to the testis or the tip of the penis in the male and the labium majus in the female. Sometimes ureteral pain is referred along the femoral branch of the genitofemoral nerve (L1 and 2) so that pain is experienced in the front of the thigh. The pain is often so severe that afferent pain impulses spread within the central nervous system, giving rise to nausea P.267
Embryologic Notes Development of the Kidneys and Ureters Three sets of structures in the urinary system appear, called the pronephros, mesonephros, and metanephros. In the human, the metanephros is responsible for the permanent kidney. The metanephros develops from two sources: the ureteric bud from the mesonephric duct and the metanephrogenic cap from the intermediate cell mass of mesenchyme of the lower lumbar and sacral regions. Ureteric Bud The ureteric bud arises as an outgrowth of the mesonephric duct (Figs. 5-68 and 5-69). It forms the ureter, which dilates at its upper end to form the pelvis of the ureter. The pelvis later gives off branches that form the major calyces, and these in turn divide and branch to form the minor calyces and the collecting tubules. Metanephrogenic Cap The metanephrogenic cap condenses around the ureteric bud (Fig. 5-69) and forms the glomerular capsules, the proximal and distal convoluted tubules, and the loops of Henle. The glomerular capsule becomes invaginated by a cluster of capillaries that form the glomerulus. Each distal convoluted tubule formed from the metanephrogenic cap tissue becomes joined to a collecting tubule derived from the ureteric bud. The surface of the kidney is lobulated at first, but after birth, this lobulation usually soon disappears. The developing kidney is initially a pelvic organ and receives its blood supply from the pelvic continuation of the aorta, the middle sacral artery. Later, the kidneys “ascend” up the posterior abdominal wall. This so-called ascent is caused mainly by the growth of the body in the lumbar and sacral regions and by the straightening of its curvature. The ureter elongates as the ascent continues. The kidney is vascularized at successively higher levels by successively higher lateral splanchnic arteries, branches of the aorta. The kidneys reach their final position opposite the second lumbar vertebra. Because of the large size of the right lobe of the liver, the right kidney lies at a slightly lower level than the left kidney. Polycystic Kidney A hereditary disease, polycystic kidneys can be transmitted by either parent. It may be associated with congenital cysts of the liver, pancreas, and lung. Both kidneys are enormously enlarged and riddled with cysts. Polycystic kidney is thought to be caused by a failure of union between the developing convoluted tubules and collecting tubules. The accumulation of urine in the proximal tubules results in the formation of retention cysts. Pelvic Kidney In pelvic kidney, the kidney is arrested in some part of its normal ascent; it usually is found at the brim of the pelvis (Fig. 5-70). Such a kidney may present with no signs or symptoms and may function normally. However, should an ectopic kidney become inflamed, it may—because of its unusual position—give rise to a mistaken diagnosis. Horseshoe Kidney When the caudal ends of both kidneys fuse as they develop, the result is horseshoe kidney (Fig. 5-70). Both kidneys commence to ascend from the pelvis, but the interconnecting bridge becomes trapped behind the inferior mesenteric artery so that the kidneys come to rest in the low lumbar region. Both ureters are kinked as they pass inferiorly over the bridge of renal tissue, producing urinary stasis, which may result in infection and stone formation. Surgical division of the bridge corrects the condition. Unilateral Double Kidney The kidney on one side may be double, with separate ureters and blood vessels. In unilateral double kidney, the ureteric bud on one side crosses the midline as it ascends, and its upper pole fuses with the lower pole of the normally placed kidney (Fig. 5-70). Here again, angulation of the ureter may result in stasis of the urine and may require surgical treatment. Rosette Kidney Both kidneys may fuse together at their hila, and they usually remain in the pelvis. The two kidneys together form a rosette (Fig. 5-70). This is the result of the early fusion of the two ureteric buds in the pelvis. Supernumerary Renal Arteries Supernumerary renal arteries are relatively common. They represent persistent fetal renal arteries, which grow in sequence from the aorta to supply the kidney as it ascends from the pelvis. Their occurrence is clinically important because a supernumerary artery may cross the pelviureteral junction and obstruct the outflow of urine, producing dilatation of the calyces and pelvis, a condition known as hydronephrosis (Fig. 5-70). Double Pelvis Double pelvis of the ureter is usually unilateral (Fig. 5-71). The upper pelvis is small and drains the upper group of calyces; the larger lower pelvis drains the middle and lower groups of calyces. The cause is a premature division of the ureteric bud near its termination. Bifid Ureter In bifid ureter, the ureters may join in the lower third of their course, may open through a common orifice into the bladder, or may open independently into the bladder (Fig. 5-71). In the latter case, one ureter crosses its fellow and may produce urinary obstruction. The cause of bifid ureter is a premature division of the ureteric bud. Cases of double pelvis and double ureters may be found by chance on radiologic investigation of the urinary tract. They are more liable to become infected or to be the seat of calculus formation than a normal ureter. Megaloureter Megaloureter may be unilateral or bilateral and shows complete absence of motility (Fig. 5-71). The cause is unknown. Because of the urinary stasis, the ureter is prone to infection. Plastic surgery is required to improve the rate of drainage. Postcaval Ureter The right ureter may ascend posterior to the inferior vena cava and may be obstructed by it (Fig. 5-71). Surgical rerouting of the ureter with reimplantation of the distal end into the bladder is the treatment of choice. P.268

Figure 5-68 The origins and positions of the pronephros, mesonephros, and metanephros.

P.269

Figure 5-69 The origin of the ureteric bud from the mesonephric duct and the formation of the major and minor calyces and the collecting tubules. Arrow indicates the point of union between the collecting tubules and the convoluted tubules.

Suprarenal Glands Location and Description The two suprarenal glands are yellowish retroperitoneal organs that lie on the upper poles of the kidneys. They are surrounded by renal fascia (but are separated from the kidneys by the perirenal fat). Each gland has a yellow cortex and a dark brown medulla. The cortex of the suprarenal glands secretes hormones that include mineral corticoids, which are concerned with the control of fluid and electrolyte balance; glucocorticoids, which are concerned with the control of the metabolism of carbohydrates, fats, and proteins; and small amounts of sex hormones, which probably play a role in the prepubertal development of the sex organs. The medulla of the suprarenal glands secretes the catecholamines epinephrine and norepinephrine. The right suprarenal gland is pyramid shaped and caps the upper pole of the right kidney (Fig. 5-4). It lies behind the right lobe of the liver and extends medially behind the inferior vena cava. It rests posteriorly on the diaphragm. The left suprarenal gland is crescentic in shape and extends along the medial border of the left kidney from the upper pole to the hilus (Fig. 5-4). It lies behind the pancreas, the lesser sac, and the stomach and rests posteriorly on the diaphragm. Blood Supply Arteries The arteries supplying each gland are three in number: inferior phrenic artery, aorta, and renal artery. Veins A single vein emerges from the hilum of each gland and drains into the inferior vena cava on the right and into the renal vein on the left. Lymph Drainage The lymph drains into the lateral aortic nodes. Nerve Supply Preganglionic sympathetic fibers derived from the splanchnic nerves supply the glands. Most of the nerves end in the medulla of the gland. Clinical Notes Cushing’s Syndrome Suprarenal cortical hyperplasia is the most common cause of Cushing’s syndrome, the clinical manifestations of which include moon-shaped face, truncal obesity, abnormal hairiness (hirsutism), and hypertension; if the syndrome occurs later in life, it may result from an adenoma or carcinoma of the cortex. Addison’s Disease Adrenocortical insufficiency (Addison’s disease), which is characterized clinically by increased pigmentation, muscular weakness, weight loss, and hypotension, may be caused by tuberculous destruction or bilateral atrophy of both cortices.

Figure 5-70 Some common congenital anomalies of the kidney.

Pheochromocytoma Pheochromocytoma, a tumor of the medulla, produces a paroxysmal or sustained hypertension. The symptoms and signs result from the production of a large amount of catecholamines, which are then poured into the bloodstream. Because of their position on the posterior abdominal wall, few tumors of the suprarenal glands can be palpated. Computed tomography (CT) scans can be used to visualize the glandular enlargement; however, when interpreting CT scans, remember the close relationship of the suprarenal glands to the crura of the diaphragm. Surgical Significance of the Renal Fascia The suprarenal glands, together with the kidneys, are enclosed within the renal fascia; the suprarenal glands, however, lie in a separate compartment, which allows the two organs to be separated easily at operation. P.270
P.271

Figure 5-71 Some common congenital anomalies of the ureter.

Embryologic Notes Development of the Suprarenal Glands The cortex develops from the coelomic mesothelium covering the posterior abdominal wall. At first, a fetal cortex is formed; later, it becomes covered by a second final cortex. After birth, the fetal cortex retrogresses, and its involution is largely completed in the first few weeks of life. The medulla is formed from the sympathochromaffin cells of the neural crest. These invade the cortex on its medial side. By this means, the medulla comes to occupy a central position and is arranged in cords and clusters. Preganglionic sympathetic nerve fibers grow into the medulla and influence the activity of the medullary cells. Susceptibility to Trauma at Birth At birth, the suprarenal glands are relatively large because of the presence of the fetal cortex; later, when this part of the cortex involutes, the gland becomes reduced in size. During the process of involution, the cortex is friable and susceptible to damage and severe hemorrhage. Arteries on the Posterior Abdominal Wall Aorta Location and Description The aorta enters the abdomen through the aortic opening of the diaphragm in front of the 12th thoracic vertebra (Fig. 5-72). It descends behind the peritoneum on the anterior surface of the bodies of the lumbar vertebrae. At the level of the fourth lumbar vertebra, it divides into the two common iliac arteries (Fig. 5-72). On its right side lie the inferior vena cava, the cisterna chyli, and the beginning of the azygos vein. On its left side lies the left sympathetic trunk. The surface markings of the aorta are shown in Figure 5-73. Branches (Fig. 5-72)

  • Three anterior visceral branches: the celiac artery, superior mesenteric artery, and inferior mesenteric artery
  • Three lateral visceral branches: the suprarenal artery, renal artery, and testicular or ovarian artery P.272
    Figure 5-72 Aorta and inferior vena cava.
    Figure 5-73 Surface markings of the aorta and its branches and the inferior vena cava on the anterior abdominal wall.

    P.273

    Diagram 5-1 Branches of Abdominal Aorta
  • Five lateral abdominal wall branches: the inferior phrenic artery and four lumbar arteries
  • Three terminal branches: the two common iliac arteries and the median sacral artery

These branches are summarized in Diagram 5-1. Clinical Notes Aortic Aneurysms Localized or diffuse dilatations of the abdominal part of the aorta (aneurysms) usually occur below the origin of the renal arteries. Most result from atherosclerosis, which causes weakening of the arterial wall, and occur most commonly in elderly men. Large aneurysms should be surgically excised and replaced with a prosthetic graft. Embolic Blockage of the Abdominal Aorta The bifurcation of the abdominal aorta where the lumen suddenly narrows may be a lodging site for an embolus discharged from the heart. Severe ischemia of the lower limbs results. Common Iliac Arteries The right and left common iliac arteries are the terminal branches of the aorta. They arise at the level of the fourth lumbar vertebra and run downward and laterally along the P.274
medial border of the psoas muscle (Figs. 5-63 and 5-72). Each artery ends in front of the sacroiliac joint by dividing into the external and internal iliac arteries. At the bifurcation, the common iliac artery on each side is crossed anteriorly by the ureter (Fig. 5-72). External Iliac Artery The external iliac artery runs along the medial border of the psoas, following the pelvic brim (Fig. 5-63). It gives off the inferior epigastric and deep circumflex iliac branches (Fig. 5-72). The artery enters the thigh by passing under the inguinal ligament to become the femoral artery. The inferior epigastric artery arises just above the inguinal ligament. It passes upward and medially along the medial margin of the deep inguinal ring (Fig. 4-4) and enters the rectus sheath behind the rectus abdominis muscle. The deep circumflex iliac artery arises close to the inferior epigastric artery (Fig. 5-72). It ascends laterally to the anterior superior iliac spine and the iliac crest, supplying the muscles of the anterior abdominal wall. Internal Iliac Artery The internal iliac artery passes down into the pelvis in front of the sacroiliac joint (Fig. 5-72). Its further course is described on page 328. Clinical Notes Obliteration of the Abdominal Aorta and Iliac Arteries Gradual occlusion of the bifurcation of the abdominal aorta, produced by atherosclerosis, results in the characteristic clinical symptoms of pain in the legs on walking (claudication) and impotence, the latter caused by lack of blood in the internal iliac arteries. In otherwise healthy individuals, surgical treatment by thromboendarterectomy or a bypass graft should be considered. Because the progress of the disease is slow, some collateral circulation is established, but it is physiologically inadequate. However, the collateral blood flow does prevent tissue death in both lower limbs, although skin ulcers may occur. The collateral circulation of the abdominal aorta is shown in Figure 5-74. Veins on the Posterior Abdominal Wall Inferior Vena Cava Location and Description The inferior vena cava conveys most of the blood from the body below the diaphragm to the right atrium of the heart. It is formed by the union of the common iliac veins behind the right common iliac artery at the level of the fifth lumbar vertebra (Fig. 5-72). It ascends on the right side of the aorta, pierces the central tendon of the diaphragm at the level of the eighth thoracic vertebra, and drains into the right atrium of the heart. The right sympathetic trunk lies behind its right margin and the right ureter lies close to its right border. The entrance into the lesser sac separates the inferior vena cava from the portal vein (Fig. 5-7). The surface markings of the inferior vena cava are shown in Figure 5-73. Tributaries The inferior vena cava has the following tributaries (Fig. 5-72):

  • Two anterior visceral tributaries: the hepatic veins
  • Three lateral visceral tributaries: the right suprarenal vein (the left vein drains into the left renal vein), renal veins, and right testicular or ovarian vein (the left vein drains into the left renal vein)
  • Five lateral abdominal wall tributaries: the inferior phrenic vein and four lumbar veins
  • Three veins of origin: two common iliac veins and the median sacral vein

The tributaries of the inferior vena cava are summarized in Diagram 5-2. If one remembers that the venous blood from the abdominal portion of the gastrointestinal tract drains to the liver by means of the tributaries of the portal vein, and that the left suprarenal and testicular or ovarian veins drain first into the left renal vein, then it is apparent that the tributaries of the inferior vena cava correspond rather closely to the branches of the abdominal portion of the aorta. Clinical Notes Trauma to the Inferior Vena Cava Injuries to the inferior vena cava are commonly lethal, despite the fact that the contained blood is under low pressure. The anatomic inaccessibility of the vessel behind the liver, duodenum, and mesentery of the small intestine and the blocking presence of the right costal margin make a surgical approach difficult. Moreover, the thin wall of the vena cava makes it prone to extensive tears. Because of the multiple anastomoses of the tributaries of the inferior vena cava (Fig. 5-75), it is impossible in an emergency to ligate the vessel. Most patients have venous congestion of the lower limbs. Compression of the Inferior Vena Cava The inferior vena cava is commonly compressed by the enlarged uterus during the later stages of pregnancy. This produces edema of the ankles and feet and temporary varicose veins. Malignant retroperitoneal tumors can cause severe compression and eventual blockage of the inferior vena cava. This results in the dilatation of the extensive anastomoses of the tributaries (Fig. 5-75). This alternative pathway for the blood to return to the right atrium of the heart is commonly referred to as the caval–caval shunt. The same pathway comes into effect in patients with a superior mediastinal tumor compressing the superior vena cava. Clinically, the enlarged subcutaneous anastomosis between the lateral thoracic vein, a tributary of the axillary vein, and the superficial epigastric vein, a tributary of the femoral vein, may be seen on the thoracoabdominal wall (Fig. 5-75). P.275

Figure 5-74 The possible collateral circulations of the abdominal aorta. Note the great dilatation of the mesenteric arteries and their branches, which occurs if the aorta is slowly blocked just below the level of the renal arteries (black bar).

P.276

Diagram 5-2 Tributaries of Inferior Vena Cava

Inferior Mesenteric Vein The inferior mesenteric vein is a tributary of the portal circulation. It begins halfway down the anal canal as the superior rectal vein (Figs. 5-22, 5-26, and 5-48). It passes up the posterior abdominal wall on the left side of the inferior mesenteric artery and the duodenojejunal flexure and joins the splenic vein behind the pancreas. It receives tributaries that correspond to the branches of the artery. Splenic Vein The splenic vein is a tributary of the portal circulation. It begins at the hilum of the spleen by the union of several veins and is then joined by the short gastric and the left gastroepiploic veins (Figs. 5-22 and 5-48). It passes to the right within the splenicorenal ligament and runs behind the pancreas. It joins the superior mesenteric vein behind the neck of the pancreas to form the portal vein. It is joined by veins from the pancreas and the inferior mesenteric vein. Superior Mesenteric Vein The superior mesenteric vein is a tributary of the portal circulation (Figs. 5-22, 5-26, and 5-48). It begins at the ileocecal junction and runs upward on the posterior abdominal wall within the root of the mesentery of the small intestine and on the right side of the superior mesenteric artery. It passes in front of the third part of the duodenum and behind the neck of the pancreas, where it joins the splenic vein to form the portal vein. It receives tributaries that correspond to the branches of the superior mesenteric artery and also receives the inferior pancreaticoduodenal vein and the right gastroepiploic vein (Fig. 5-22). Portal Vein The portal vein is described on page 245. Lymphatics on the Posterior Abdominal Wall Lymph Nodes The lymph nodes are closely related to the aorta and form a preaortic and a right and left lateral aortic (para-aortic or lumbar) chain (Fig. 5-76). The preaortic lymph nodes lie around the origins of the celiac, superior mesenteric, and inferior mesenteric arteries and are referred to as the celiac, superior mesenteric, and inferior mesenteric lymph nodes, respectively. They drain the lymph from the gastrointestinal tract, extending from the lower one third of the esophagus to halfway down the anal canal, and from the spleen, pancreas, gallbladder, and greater part of the liver. The efferent lymph vessels form the large intestinal trunk (see Fig. 1-18 and below). The lateral aortic (para-aortic or lumbar) lymph nodes drain lymph from the kidneys and suprarenals; from the testes in the male and from the ovaries, uterine tubes, and fundus of the uterus in the female; from the deep lymph vessels of the abdominal walls; and from the common iliac nodes. The efferent lymph vessels form the right and left lumbar trunks (see Fig. 1-18 and below). Lymph Vessels The thoracic duct commences in the abdomen as an elongated lymph sac, the cisterna chyli. This lies just below the diaphragm in front of the first two lumbar vertebrae and on the right side of the aorta (Fig. 5-76). P.277

Figure 5-75 The possible collateral circulations of the superior and inferior venae cavae. Note the alternative pathways that exist for blood to return to the right atrium of the heart if the superior vena cava becomes blocked below the entrance of the azygos vein (upper black bar). Similar pathways exist if the inferior vena cava becomes blocked below the renal veins (lower black bar). Note also the connections that exist between the portal circulation and the systemic veins in the anal canal.

P.278

Figure 5-76 Lymph vessels and nodes on the posterior abdominal wall.

The cisterna chyli receives the intestinal trunk, the right and left lumbar trunks, and some small lymph vessels that descend from the lower part of the thorax. Lymphatic Drainage of the Gonads The importance of the lymph drainage of the testis was emphasized on page 169. Nerves on the Posterior Abdominal Wall Lumbar Plexus The lumbar plexus, which is one of the main nervous pathways supplying the lower limb, is formed in the psoas muscle from the anterior rami of the upper four lumbar nerves (Fig. 5-77). The anterior rami receive gray rami communicantes from the sympathetic trunk, and the upper two give off white rami communicantes to the sympathetic trunk. The branches of the plexus emerge from the lateral and medial borders of the muscle and from its anterior surface. The iliohypogastric nerve, ilioinguinal nerve, lateral cutaneous nerve of the thigh, and femoral nerve emerge from the lateral border of the psoas, in that order from above downward (Fig. 5-34). The iliohypogastric and ilioinguinal nerves (L1) enter the lateral and anterior abdominal walls (see page 157). The iliohypogastric nerve supplies the skin of the lower part of the anterior abdominal wall, and the ilioinguinal nerve passes through the inguinal canal to supply the skin of the groin and the scrotum or labium majus. The lateral cutaneous nerve of the thigh crosses the iliac fossa in front of the iliacus muscle and enters the thigh behind the lateral end of the inguinal ligament (see page 568). It supplies the skin over the lateral surface of the thigh. The femoral nerve (L2, 3, and 4) is the largest branch of the lumbar plexus. It runs downward and laterally between the psoas and the iliacus muscles and enters the thigh behind the inguinal ligament and lateral to the femoral vessels and the femoral sheath. In the abdomen it supplies the iliacus muscle. P.279

Figure 5-77 Lumbar plexus of nerves.

The obturator nerve and the fourth lumbar root of the lumbosacral trunk emerge from the medial border of the psoas at the brim of the pelvis. The obturator nerve (L2, 3, and 4) crosses the pelvic brim in front of the sacroiliac joint and behind the common iliac vessels. It leaves the pelvis by passing through the obturator foramen into the thigh. (For a description of its course in the pelvis see page 326 and in the thigh see page 586). The fourth lumbar root of the lumbosacral trunk takes part in the formation of the sacral plexus (see page 325). It descends anterior to the ala of the sacrum and joins the first sacral nerve.

Table 5-1 Branches of the Lumbar Plexus and Their Distribution
Branches Distribution
Iliohypogastric nerve External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall; skin over lower anterior abdominal wall and buttock
Ilioinguinal nerve External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall; skin of upper medial aspect of thigh; root of penis and scrotum in the male; mons pubis and labia majora in the female
Lateral cutaneous nerve of the thigh Skin of anterior and lateral surfaces of the thigh
Genitofemoral nerve (L1, 2) Cremaster muscle in scrotum in male; skin over anterior surface of thigh; nervous pathway for cremasteric reflex
Femoral nerve (L2, 3, 4) Iliacus, pectineus, sartorius, quadriceps femoris muscles, and intermediate cutaneous branches to the skin of the anterior surface of the thigh and by saphenous branch to the skin of the medial side of the leg and foot; articular branches to hip and knee joints
Obturator nerve (L2, 3, 4) Gracilis, adductor brevis, adductor longus, obturator externus, pectineus, adductor magnus (adductor portion), and skin on medial surface of thigh; articular branches to hip and knee joints
Segmental branches Quadratus lumborum and psoas muscles

The genitofemoral nerve (L1 and 2) emerges on the anterior surface of the psoas. It runs downward in front of the muscle and divides into a genital branch, which enters the spermatic cord and supplies the cremaster muscle, and a femoral branch, which supplies a small area of the skin of the thigh (see page 568). It is the nervous pathway involved in the cremasteric reflex, in which stimulation of the skin of the thigh in the male results in reflex contraction of the cremaster muscle and the drawing upward of the testis within the scrotum. The branches of the lumbar plexus and their distribution are summarized in Table 5-1. Sympathetic Trunk (Abdominal Part) The abdominal part of the sympathetic trunk is continuous above with the thoracic and below with the pelvic parts of the sympathetic trunk. It runs downward along the medial border of the psoas muscle on the bodies of the lumbar vertebrae (Fig. 5-78). It enters the abdomen from behind the medial arcuate ligament and gains entrance to the pelvis below by passing behind the common iliac vessels. The right sympathetic trunk lies behind the right border of the inferior vena cava; the left sympathetic trunk lies close to the left border of the aorta. The sympathetic trunk possesses four or five segmentally arranged ganglia, the first and second often being fused together. Branches

  • White rami communicantes join the first two ganglia to the first two lumbar spinal nerves. A white ramus contains preganglionic nerve fibers and afferent sensory nerve fibers.
  • Gray rami communicantes join each ganglion to a corresponding lumbar spinal nerve. A gray ramus contains postganglionic nerve fibers. The postganglionic fibers are P.280
    distributed through the branches of the spinal nerves to the blood vessels, sweat glands, and arrector pili muscles of the skin (see Fig. 1-4).
    Figure 5-78 Aorta and related sympathetic plexuses.
  • Fibers pass medially to the sympathetic plexuses on the abdominal aorta and its branches. (These plexuses also receive fibers from splanchnic nerves and the vagus.)
  • Fibers pass downward and medially in front of the common iliac vessels into the pelvis, where, together with branches from sympathetic nerves in front of the aorta, they form a large bundle of fibers called the superior hypogastric plexus (Fig. 5-78).

Aortic Plexuses Preganglionic and postganglionic sympathetic fibers, preganglionic parasympathetic fibers, and visceral afferent fibers form a plexus of nerves, the aortic plexus, around the abdominal part of the aorta (Fig. 5-78). Regional concentrations of this plexus around the origins of the celiac, renal, superior mesenteric, and inferior mesenteric arteries form the celiac plexus, renal plexus, superior mesenteric plexus, and inferior mesenteric plexus, respectively. The celiac plexus consists mainly of two celiac ganglia connected together by a large network of fibers that surrounds the origin of the celiac artery. The ganglia receive the greater and lesser splanchnic nerves (preganglionic sympathetic fibers). Postganglionic branches accompany the branches of the celiac artery and follow them to their distribution. Parasympathetic vagal fibers also accompany the branches of the artery. The renal and superior mesenteric plexuses are smaller than the celiac plexus. They are distributed along the branches of the corresponding arteries. The inferior mesenteric plexus is similar but receives parasympathetic fibers from the sacral parasympathetic. Clinical Notes Lumbar Sympathectomy Lumbar sympathectomy is performed mainly to produce a vasodilatation of the arteries of the lower limb in patients with vasospastic disorders. The preganglionic sympathetic fibers that supply the vessels of the lower limb leave the spinal cord from segments T11 to L2. They synapse in the lumbar and sacral ganglia of the sympathetic trunks. The postganglionic fibers join the lumbar and sacral nerves and are distributed to the vessels of the limb as branches of these nerves. Additional postganglionic fibers pass directly from the lumbar ganglia to the common and external iliac arteries, but they follow the latter artery only down as far as the inguinal ligament. In the male a bilateral lumbar sympathectomy may be followed by loss of ejaculatory power, but erection is not impaired. Abdominal Pain Abdominal pain is one of the most important problems facing the physician. This section provides an anatomic basis for the different forms of abdominal pain found in clinical practice. Three distinct forms of pain exist: somatic, visceral, and referred pain. Somatic Abdominal Pain Somatic abdominal pain in the abdominal wall can arise from the skin, fascia, muscles, and parietal peritoneum. It can be severe and precisely localized. When the origin is on one side of the midline, the pain is also lateralized. The somatic pain impulses from the abdomen reach the central nervous system in the following segmental spinal nerves:

  • Central part of the diaphragm: Phrenic nerve (C3, 4, and 5)
  • Peripheral part of the diaphragm: Intercostal nerves (T7 to 11)
  • Anterior abdominal wall: Thoracic nerves (T7 to 12) and the first lumbar nerve
  • Pelvic wall: Obturator nerve (L2, 3, and 4)

The inflamed parietal peritoneum is extremely sensitive, and because the full thickness of the abdominal wall is innervated by the same nerves, it is not surprising to find cutaneous hypersensitivity (hyperesthesia) and tenderness. Local reflexes involving the same nerves bring about a protective phenomenon in which the abdominal muscles increase in tone. This increased tone or rigidity, sometimes called guarding, is an attempt to rest and localize the inflammatory process. Rebound tenderness occurs when the parietal peritoneum is inflamed. Any movement of that inflamed peritoneum, even when that movement is elicited by removing the examining hand from a site distant from the inflamed peritoneum, brings about tenderness. Examples of acute, severe, localized pain originating in the parietal peritoneum are seen in the later stages of appendicitis. Cutaneous hyperesthesia, tenderness, and muscular spasm or rigidity occur in the lower right quadrant of the anterior abdominal wall. A perforated peptic ulcer, in which the parietal peritoneum is chemically irritated, produces the same symptoms and signs but involves the right upper and lower quadrants. Visceral Abdominal Pain Visceral abdominal pain arises in abdominal organs, visceral peritoneum, and the mesenteries. The causes of visceral pain include stretching of a viscus or mesentery, distention of a hollow viscus, impaired blood supply (ischemia) to a viscus, and chemical damage (e.g., acid gastric juice) to a viscus or its covering peritoneum. Pain arising from an abdominal viscus is dull and poorly localized. Visceral pain is referred to the midline, probably because the viscera develop embryologically as midline structures and receive a bilateral nerve supply; many viscera later move laterally as development proceeds, taking their nerve supply with them. Colic is a form of visceral pain produced by the violent contraction of smooth muscle; it is commonly caused by luminal obstruction as in intestinal obstruction, in the passage of a gallstone in the biliary ducts, or in the passage of a stone in the ureters. Many visceral afferent fibers that enter the spinal cord participate in reflex activity. Reflex sweating, salivation, nausea, vomiting, and increased heart rate may accompany visceral pain. The sensations that arise in viscera reach the central nervous system in afferent nerves that accompany the sympathetic nerves and enter the spinal cord through the posterior roots. The significance of this pathway is better understood in the following discussion on referred visceral pain. Referred Abdominal Pain Referred abdominal pain is the feeling of pain at a location other than the site of origin of the stimulus but in an area supplied by the same or adjacent segments of the spinal cord. Both somatic and visceral structures can produce referred pain. In the case of referred somatic pain, the possible explanation is that the nerve fibers from the diseased structure and the area where the pain is felt ascend in the central nervous system along a common pathway, and the cerebral cortex is incapable of distinguishing between the sites. Examples of referred somatic pain follow. Pleurisy involving the lower part of the costal parietal pleura can give rise to referred pain in the abdomen because the lower parietal pleura receives its sensory innervation from the lower five intercostal nerves, which also innervate the skin and muscles of the anterior abdominal wall. Visceral pain from the stomach is commonly referred to the epigastrium (Fig. 5-79). The afferent pain fibers from the stomach ascend in company with the sympathetic nerves and pass through the celiac plexus and the greater splanchnic nerves. The sensory fibers enter the spinal cord at segments T5 to 9 and give rise to referred pain in dermatomes T5 to 9 on the lower chest and abdominal walls. Visceral pain from the appendix (Fig. 5-79), which is produced by distension of its lumen or spasm of its smooth muscle coat, travels in nerve fibers that accompany sympathetic nerves through the superior mesenteric plexus and the lesser splanchnic nerve to the spinal cord (T10 segment). The vague referred pain is felt in the region of the umbilicus (T10 dermatome). Later, if the inflammatory process involves the parietal peritoneum, the severe somatic pain dominates the clinical picture and is localized precisely in the right lower quadrant. Visceral pain from the gallbladder, as occurs in patients with cholecystitis or gallstone colic, travels in nerve fibers that accompany sympathetic nerves. They pass through the celiac plexus and greater splanchnic nerves to the spinal cord (segments T5 to 9). The vague referred pain is felt in the dermatomes (T5 to 9) on the lower chest and upper abdominal walls (Fig. 5-79). If the inflammatory process spreads to involve the parietal peritoneum of the anterior abdominal wall or peripheral diaphragm, the severe somatic pain is felt in the right upper quadrant and through to the back below the inferior angle of the scapula. Involvement of the central diaphragmatic parietal peritoneum, which is innervated by the phrenic nerve (C3, 4, and 5), can give rise to referred pain over the shoulder because the skin in this area is innervated by the supraclavicular nerves (C3 and 4).

Figure 5-79 Some important skin areas involved in referred visceral pain.

P.281
P.282
Cross-Sectional Anatomy of the Abdomen To assist in interpretation of computed tomography (CT) scans of the abdomen, study the labeled cross sections of the abdomen shown in Figures 5-80 and 5-81. The sections have been photographed on their inferior surfaces. Also see Figure 5-82 for an example of a CT scan. Radiographic Anatomy Radiographic Appearances of the Abdomen Only the more important features seen in a standard anteroposterior radiograph of the abdomen, with the patient in the supine position, are described (Figs. 5-83 and 5-84). Examine the following in a systematic order.

  • Bones. In the upper part of the radiograph the lower ribs are seen. Running down the middle of the radiograph are the lower thoracic and lumbar vertebrae and the sacrum and coccyx. On either side are the sacroiliac joints, the pelvic bones, and the hip joints.
  • Diaphragm. This casts dome-shaped shadows on each side; the one on the right is slightly higher than the one on the left (not shown in Fig. 5-83).
  • Psoas muscle. On either side of the vertebral column, the lateral borders of the psoas muscle cast a shadow that passes downward and laterally from the 12th thoracic vertebra.
  • Liver. This forms a homogeneous opacity in the upper part of the abdomen.
  • Spleen. This may cast a soft shadow, which can be seen in the left 9th and 10th intercostal spaces (not shown in Fig. 5-83).
  • Kidneys. These are usually visible because the perirenal fat surrounding the kidneys produces a transradiant line.
  • Stomach and intestines. Gas may be seen in the fundus of the stomach and in the intestines. Fecal material may also be seen in the colon.
  • Urinary bladder. If this contains sufficient urine, it will cast a shadow in the pelvis.

Radiographic Appearances of the Gastrointestinal Tract Stomach The stomach can be demonstrated radiologically (Figs. 5-85 and 5-86) by the administration of a watery suspension of barium sulfate (barium meal). With the patient in the erect position, the first few mouthfuls pass into the stomach and form a triangular shadow with the apex downward. The gas bubble in the fundus shows above the fluid level at the top of the barium shadow. As the stomach is filled, the greater and lesser curvatures are outlined and the body and pyloric portions are recognized. The pylorus is seen to move downward and come to lie at the level of the third lumbar vertebra. Fluoroscopic examination of the stomach as it is filled with the barium emulsion reveals peristaltic waves of contraction of the stomach wall, which commence near the middle of the body and pass to the pylorus. The respiratory movements of the diaphragm cause displacement of the fundus. Duodenum A barium meal passes into the first part of the duodenum and forms a triangular homogeneous shadow, the duodenal cap, which has its base toward the pylorus (Fig. 5-87). P.283
Under the influence of peristalsis, the barium quickly leaves the duodenal cap and passes rapidly through the remaining portions of the duodenum. The outline of the barium shadow in the first part of the duodenum is smooth because of the absence of mucosal folds. In the remainder of the duodenum, the presence of plicae circulares breaks up the barium emulsion, giving it a floccular appearance.

Figure 5-80 A. Cross section of the abdomen at the level of the body of the 11th thoracic vertebra, viewed from below. Note that the large size of the pleural cavity is an artifact caused by the embalming process. B. Cross section of the abdomen at the level of the body of the second lumbar vertebra, viewed from below.

P.284

Figure 5-81 Cross section of the abdomen at the level of the body of the third lumbar vertebra, viewed from below.
Figure 5-82 Computed tomography scan of the abdomen at the level of the second lumbar vertebra after intravenous pyelography. The radiopaque material can be seen in the renal pelvis and the ureters. The section is viewed from below.

P.285

Figure 5-83 Anteroposterior radiograph of the abdomen.

P.286

Figure 5-84 Representation of the main features seen in the anteroposterior radiograph in Figure 5-83.

P.287

Figure 5-85 Anteroposterior radiograph of the stomach and the small intestine after ingestion of barium meal.

P.288

Figure 5-86 Representation of the main features seen in the radiograph in Figure 5-85.

P.289

Figure 5-87 Anteroposterior radiograph of the duodenum after ingestion of barium meal.

Jejunum and Ileum A barium meal enters the jejunum in a few minutes and reaches the ileocecal junction in 30 minutes to 2 hours, and the greater part has left the small intestine in 6 hours. In the jejunum and upper part of the ileum, the mucosal folds and the peristaltic activity scatter the barium shadow (Figs. 5-85 and 5-88). In the last part of the ileum, the barium meal tends to form a continuous mass of barium. Large Intestine The large intestine can be demonstrated by the administration of a barium enema or a barium meal. The former is more satisfactory. The bowel may be outlined by the administration of 2 to 3 pints (1 L) of barium sulfate emulsion through the anal canal. When the large intestine is filled, the entire outline can be seen in an anteroposterior projection (Figs. 5-89 and 5-90). Oblique and lateral views of the colic flexures may be necessary. The characteristic sacculations are well seen when the bowel is filled, and, after the enema has been evacuated, the mucosal pattern is clearly demonstrated. The appendix frequently fills with barium after an enema. The radiographic appearances of the sigmoid colon and rectum are described on page 377. The arterial supply to the gastrointestinal tract can be demonstrated by arteriography. A catheter is inserted into the femoral artery and threaded upward under direct vision on a screen into the abdominal aorta. The end of the catheter is then manipulated into the opening of the appropriate artery. Radiopaque material is injected through the catheter and an arteriogram is obtained (Fig. 5-91). Radiographic Appearances of the Biliary Ducts The bile passages normally are not visible on a radiograph. Their lumina can be outlined by the administration of various iodine-containing compounds orally or by injection. When taken orally, the compound is absorbed from the small intestine, carried to the liver, and excreted with the bile. On reaching the gallbladder, it is concentrated with the bile. The concentrated iodine compound, mixed with the bile, is now radiopaque and reveals the gallbladder as a pear-shaped opacity in the angle between the right 12th rib and the vertebral column (Figs. 5-92 and 5-93). If the patient is given a fatty meal, the gallbladder contracts, and the cystic and bile ducts become visible as the opaque medium passes down to the second part of the duodenum. P.290

Figure 5-88 Anteroposterior radiograph of the small intestine after ingestion of barium meal.

P.291

Figure 5-89 Anteroposterior radiograph of the large intestine after a barium enema.

P.292

Figure 5-90 Anteroposterior radiograph of the large intestine after a barium enema. Air has been introduced into the intestine through the enema tube after evacuation of most of the barium. This procedure is referred to as a contrast enema.

P.293

Figure 5-91 An arteriogram of the superior mesenteric artery. The catheter has been inserted into the right femoral artery and has passed up the external and common iliac arteries to ascend the aorta to the origin of the superior mesenteric artery. A nasogastric tube is also in position.

P.294

Figure 5-92 Anteroposterior radiograph of the gallbladder after administration of an iodine-containing compound.

P.295

Figure 5-93 Representation of the main features seen in the radiograph in Figure 5-92.

A sonogram of the upper part of the abdomen can be used to show the lumen of the gallbladder (Fig. 5-54). Radiographic Appearances of the Urinary Tract Kidneys The kidneys are usually visible on a standard anteroposterior radiograph of the abdomen because the perirenal fat surrounding the kidneys produces a transradiant line. Calyces, Renal Pelvis, and Ureter Calyces, the renal pelvis, and the ureter are not normally visible on a standard radiograph. The lumen can be demonstrated by the use of radiopaque compounds in intravenous pyelography or retrograde pyelography. With intravenous pyelography, an iodine-containing compound is injected into a subcutaneous arm vein. It is excreted and concentrated by the kidneys, thus rendering the calyces and ureter opaque to x-rays (Figs. 5-94, 5-95, and 5-96). When enough of the opaque medium has been excreted, the bladder is also revealed. The ureters are seen superimposed on the transverse processes of the lumbar vertebrae. They cross the sacroiliac joints and enter the pelvis. In the vicinity of the ischial spines, they turn medially to enter the bladder. The three normal constrictions of the ureters (at the junction of the renal pelvis with the ureter, at the pelvic brim, and where the ureter enters the bladder) can be recognized. With retrograde pyelography, a cystoscope is passed through the urethra into the bladder, and a ureteric catheter is inserted into the ureter. A solution of sodium iodide is then injected along the catheter into the ureter. When the minor calyces become filled with the radiopaque medium, the detailed anatomic features of the minor and major calyces and the pelvis of the ureter can be clearly seen. Each minor calyx has a cup-shaped appearance caused by the renal papilla projecting into it. P.296

Figure 5-94 Anteroposterior radiograph of the ureter and renal pelvis after intravenous injection of an iodine-containing compound, which is excreted by the kidney. Major and minor calyces are also shown.

P.297

Figure 5-95 Representation of the main features seen in the radiograph in Figure 5-94.

P.298

Figure 5-96 Anteroposterior radiograph of both kidneys 15 minutes after intravenous injection of an iodine-containing compound. The calyces, the renal pelvis, and the upper parts of the ureters are clearly seen (5-year-old girl).

Surface Anatomy of the Abdominal Viscera The surface anatomy of the abdominal viscera is fully described on page 192. Clinical Problem Solving Study the following case histories and select the best answers to the question following them. A 45-year-old man was admitted to the emergency department complaining of severe pain in the right lower quadrant of the anterior abdominal wall. He had repeatedly vomited, and his temperature and pulse rate were elevated. His history indicated that he had acute appendicitis and that the pain had suddenly increased. On examination, the muscles of the lower part of the anterior abdominal wall in the right lower quadrant showed rigidity. The diagnosis of peritonitis after perforation of the appendix was made. 1. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The perforation of the appendix had resulted in the spread of the infection from the appendix to involve the parietal peritoneum. (b) The parietal peritoneum in the right iliac region, the muscles of the anterior abdominal wall, and the overlying skin are all supplied by the segmental nerves T12 and L1. (c) Irritation of the parietal peritoneum reflexly increases the tone of the abdominal muscles, causing rigidity. (d) The greater omentum tends to become stuck down to the appendix and restricts the spread of infection. (e) The pain was intensified after perforation of the appendix because of stimulation of the autonomic pain endings in the parietal peritoneum. View Answer1. E. In the parietal peritoneum lining the anterior abdominal wall in the right iliac fossa, the sensation of pain originates in the nerve endings of somatic spinal nerves (T12 and L1). A 63-year-old man with a long history of a duodenal ulcer was seen in the emergency department after vomiting blood-stained fluid and exhibiting all the signs and symptoms of severe hypovolemic shock. 2. The following statements concerning duodenal ulcers could apply to the patient’s condition except which? (a) Hemorrhage from a duodenal ulcer often reveals itself by the passage of black stools on defecation. (b) The pyloric sphincter prevents most of the blood from the duodenal lumen from passing up into the stomach. (c) The gastroduodenal artery lies behind the first part of the duodenum and was probably eroded by the ulcer. (d) The gastroduodenal artery is a small branch of the hepatic artery. (e) The duodenal ulcer was most likely to be situated on the posterior wall of the first part of the duodenum. View Answer2. D. The gastroduodenal artery is a large branch of the hepatic artery. A 47-year-old woman was operated on for the treatment of a chronic gastric ulcer that had not responded to medical treatment. At operation for partial gastrectomy, it was found that the posterior wall of the stomach was stuck down to the posterior abdominal wall. The surgeon had to proceed with great care to avoid damaging important structures lying on the posterior abdominal wall. 3. The following structures located on the posterior abdominal wall were possibly involved in the disease process except which? (a) The right kidney (b) The pancreas (c) The left suprarenal gland (d) The left kidney (e) The lesser sac of peritoneum (f) The splenic artery View Answer3. A A 58-year-old man was in a restaurant when he suddenly started to vomit blood. He was taken unconscious to the emergency department of a local hospital. On examination, he had all the signs of severe hypovolemic shock. On palpation of the anterior abdominal wall, the right lobe of the liver was felt three fingerbreadths below the costal margin. Several enlarged superficial veins could be seen around the umbilicus. His wife said that he had vomited blood 3 months previously and had nearly died. She admitted that he was a chronic alcoholic. The diagnosis was cirrhosis of the liver secondary to chronic alcoholism. 4. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The normal flow of portal blood through the liver is impaired by cirrhosis of the liver. (b) The portal–systemic anastomoses become enlarged in this condition. (c) At the lower end of the esophagus, a branch from the right gastric vein anastomoses with an esophageal tributary of the azygos vein. (d) Rupture of a varicosed esophageal vein could produce a severe hemorrhage so that the patient would vomit up blood. (e) With portal hypertension the paraumbilical veins linking the superficial veins of the skin (systemic veins) to the portal vein become congested and visible. View Answer4. C. At the lower end of the esophagus, a branch from the left gastric vein anastomoses with an esophageal tributary of the azygos vein. A 55-year-old woman with a history of flatulent dyspepsia suddenly experienced an excruciating colicky pain across the upper part of the abdomen. On examination in the emergency department, she was found to have some rigidity and tenderness in the right upper quadrant. A diagnosis of biliary colic was made. 5. The following statements would explain this patient’s symptoms except which? (a) The pain of gallstone colic is caused by spasm of the smooth muscle in the wall of the gallbladder and distention of the bile ducts by the stones. (b) The pain fibers from the gallbladder and bile ducts ascend through the superior mesenteric plexus and the greater splanchnic nerves to enter the thoracic segments of the spinal cord. (c) Referred pain is felt in the right upper quadrant or the epigastrium. (d) T7 through T9 dermatomes are involved. (e) The violent contractions of the gallbladder wall are attempts to expel the gallstones. View Answer5. B. The pain fibers from the gallbladder and bile ducts ascend through the celiac plexus. On examination of the abdomen of a 31-year-old woman, a large swelling was found to extend downward and medially below the left costal margin. On percussion, a continuous band of dullness was noted to extend upward from the left of the umbilicus to the left axillary region. On palpation, a notch was felt along the anterior border of the swelling. A diagnosis of splenic enlargement was made. 6. The signs displayed by this patient can be explained by the following statements except which? (a) The spleen has a notched anterior border caused by incomplete fusion of its parts during development. (b) Because of the presence of the left colic flexure and the phrenicocolic ligament, the spleen is unable to expand vertically downward. (c) A pathologically enlarged spleen extends downward and forward, toward the umbilicus. (d) The spleen is situated in the upper left quadrant of the abdomen beneath the diaphragm. (e) The long axis of the spleen lies along the 12th rib. View Answer6. E. The long axis of the spleen lies along the 10th rib. A 48-year-old woman with a history of repeated vomiting was admitted to the hospital with a diagnosis of large bowel obstruction. To decompress the stomach a nasogastric tube was passed. 7. When passing a nasogastric tube some important anatomic statements should be considered except which? (a) The well-lubricated tube is inserted through the wider nostril. (b) The tube is directed backward along the nasal floor and not upward because it may become caught on the nasal choanae. (c) The distance between the nostril and the cardiac orifice of the stomach is about 23 in. (57.5 cm). (d) The distance between the cardiac orifice and the pylorus is 4.8 to 5.6 in. (12 to 14 cm). (e) Esophageal narrowing may offer resistance to the tube behind the cricoid cartilage, 7.21 in. (18 cm) from the nostril. (f) The left bronchus and the arch of the aorta cross in front of the esophagus and may impede the descent of the tube, 11.2 in. (28 cm) from the nostril. (g) Where the esophagus enters the stomach is a slight resistance to the descent of the tube. View Answer7. C. The distance between the nostril and the cardiac orifice of the stomach is about 17.2 in. (44 cm). A 16-year-old boy received a severe kick in the right flank while playing football at school. On examination in the emergency department, his right flank was severely bruised, and his right costovertebral angle was extremely tender on palpation. A specimen of urine showed microscopic hematuria. A diagnosis of damage to the right kidney was made. 8. The following statements concerning blunt trauma to the kidney are correct except which? (a) The kidney tends to be crushed between the 12th rib and the vertebral column. (b) The kidney can be injured by fractures of the 12th rib (right kidney) or 11th and 12th ribs (left kidney). (c) In most patients the kidney damage is mild and results in nothing more than microscopic hematuria, as in this patient. (d) In severe kidney lacerations, extensive hemorrhage and extravasation of blood and urine into the pararenal fat occurs. (e) In severe kidney lacerations, a mass caused by extravasated blood and urine behind the peritoneum may be palpated, especially on the right side. (f) Both kidneys lie on the posterior abdominal wall and are at the same vertebral level. View Answer8. F. Because of the large size of the right lobe of the liver, the right kidney lies at a lower level than the left kidney. A 17-year-old boy was involved in a gang fight. It started as an argument but quickly worsened into a street brawl with the use of knives. He was examined in the emergency department and found to have a bleeding stab wound in his left flank. A urine specimen revealed frank blood. 9. Stab wounds of the kidneys involve other abdominal organs in a high percentage of cases. Of the organs listed, which one is least likely to be damaged in this patient? (a) Stomach (b) Spleen (c) Inferior vena cava (d) Left colic flexure (e) Left suprarenal gland (f) Coils of jejunum (g) Body of the pancreas View Answer9. C A 56-year-old man visited his physician complaining that he experiences severe pain in both legs when taking long walks. He noticed recently that the cramplike pain occurs after walking only a hundred yards. On questioning, he said that the pain quickly disappears on rest only to return after he walks the same distance. When the physician asked about his sex life the patient admitted that he was experiencing difficulty with erection. 10. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) Arteriography of the abdominal aorta revealed blockage in the region of the bifurcation. (b) Only the right common iliac artery was involved by disease. (c) The gradual blockage of the aorta was caused by advanced arteriosclerosis. (d) An insufficient amount of blood was reaching both legs, causing pain (claudication) on walking. (e) The lack of blood entering both internal iliac arteries was responsible for the difficulty with erection. View Answer10. B. The blockage of the aorta in the region of the bifurcation had effectively blocked the entrances into both common iliac arteries. A 23-year-old woman, who was 8 months pregnant, told her obstetrician that she had recently noticed that her feet and ankles were swollen at the end of the day. She said that the swelling was worse if she had been standing for long periods. She also noticed that the veins around her ankles were becoming prominent. 11. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The enlarged uterus is an abdominal organ and often compresses the inferior vena cava. (b) Venous back pressure causes the tissue fluid to accumulate in the subcutaneous tissues of the feet and ankles. (c) Venous back pressure impairs the venous return in the superficial veins in both the legs, leading to varicose veins. (d) High levels of progesterone in the blood during pregnancy cause the smooth muscle in the wall of the veins to relax, thus permitting the veins to dilate. (e) The pregnant uterus presses on the sympathetic trunks, causing vasodilatation of the blood vessels of the legs. View Answer11. E. The sympathetic trunks are not pressed on by the pregnant uterus. A 27-year-old woman was involved in a head-on automobile accident. When examined in a neighboring hospital, she was in a state of severe shock, with a rapid pulse and low blood pressure. Extensive bruising was seen on the lower part of the anterior abdominal wall. Further examination showed that the abdomen was becoming rapidly distended. Exploratory surgery revealed a ruptured abdominal aorta. 12. The following statements concerning this case would explain her clinical condition except which? (a) The patient was wearing a seat belt, which explained the bruising on the anterior abdominal wall. (b) The aorta is located on the posterior abdominal wall lateral to the left side of the vertebral column. (c) The aorta lies behind the peritoneum in the retroperitoneal space. (d) The blood did not immediately escape into the peritoneal cavity because it is retroperitoneal in position and the tear was small in size. (e) A seat belt may hold the patient securely in the seat, but in some individuals the kidneys continue forward after impact and the renal artery may be torn from the side of the aorta. View Answer12. B. The aorta descends through the abdomen behind the peritoneum on the anterior surface of the bodies of the lumbar vertebrae. P.299
P.300
P.301
P.302
P.303
P.304
P.305
P.306
Review Questions Multiple-Choice Questions Select the best answer for each question. 1. The following statements concerning the liver are correct except which? (a) The quadrate lobe drains into the right hepatic duct. (b) The lesser omentum suspends the stomach from the visceral surface of the liver. (c) The left triangular ligament of the liver lies anterior to the abdominal part of the esophagus. (d) The attachment of the hepatic veins to the inferior vena cava is one of the most important supports of the liver. (e) The ligamentum venosum is attached to the left branch of the portal vein in the porta hepatis. View Answer1. A. The quadrate lobe and the caudate lobe are in fact parts of the left lobe. Thus, the right and left branches of the hepatic artery and portal vein and the right and left hepatic ducts are distributed to the right lobe and the left lobe plus the quadrate and caudate lobes. 2. The following statements concerning the pancreas are correct except which? (a) The pancreas receives part of the arterial supply from the splenic artery. (b) The main pancreatic duct opens into the third part of the duodenum. (c) The uncinate process of the pancreas projects from the head of the pancreas. (d) The bile duct (common bile duct) lies posterior to the head of the pancreas. (e) The transverse mesocolon is attached to the anterior border of the pancreas. View Answer2. B. The main pancreatic duct opens into the second part of the duodenum, at about its middle, with the bile duct on the major duodenal papilla. Sometimes, the main duct drains separately into the duodenum. 3. The following statements concerning the ileum are correct except which? (a) The circular smooth muscle of the lower end of the ileum serves as a sphincter at the junction of the ileum and the cecum. (b) The branches of the superior mesenteric artery serving the ileum form more arcades than those serving the jejunum. (c) Peyer’s patches are present in the mucous membrane of the lower ileum along the antimesenteric border. (d) The plicae circulares are more prominent at the distal end of the ileum than in the jejunum. (e) The parasympathetic innervation of the ileum is from the vagus nerves. View Answer3. D. The plicae circulares are absent from the distal end of the ileum. 4. The hilum of the right kidney contains the following important structures except which? (a) The renal pelvis (b) Tributaries of the renal vein (c) Sympathetic nerve fibers (d) Part of the right suprarenal gland (e) Branches of the renal artery View Answer4. D. The right suprarenal gland caps the upper pole of the right kidney and does not extend downward to the hilum of the kidney. 5. The following statements concerning the left suprarenal gland are correct except which? (a) The gland extends along the medial border of the left kidney from the upper pole to the hilus. (b) The gland’s vein drains into the left renal vein. (c) The gland is separated from the left kidney by perirenal fat. (d) The gland lies behind the lesser sac of peritoneum. (e) The medulla is innervated by postganglionic sympathetic nerve fibers. View Answer5. E. The medulla of the suprarenal gland is innervated by preganglionic sympathetic nerve fibers. 6. The following statements concerning the abdominal aorta are correct except which? (a) The aorta bifurcates into the two common iliac arteries in front of the fourth lumbar vertebra. (b) The aorta lies on the right side of the inferior vena cava. (c) From the aorta’s anterior surface arise the celiac, superior mesenteric, and inferior mesenteric arteries. (d) The aorta enters the abdomen in front of the 12th thoracic vertebra. (e) The thoracic duct leaves the abdomen through the aortic opening of the diaphragm on the right side of the aorta. View Answer6. B. The abdominal aorta lies on the left side of the inferior vena cava. 7. The following statements concerning the abdominal part of the sympathetic trunk are correct except which? (a) The trunk enters the abdomen from behind the medial arcuate ligament. (b) The trunk possesses four or five segmentally arranged ganglia. (c) All the ganglia receive white rami communicantes. (d) Gray rami communicantes are given off to the lumbar spinal nerves. (e) Nerve fibers pass medially to the sympathetic plexuses on the abdominal aorta and its branches. View Answer7. C. The white rami communicantes join the first two ganglia to the first two lumbar spinal nerves. 8. The following statements concerning the lumbar plexus are correct except which? (a) The plexus lies within the psoas muscle. (b) The plexus is formed from the posterior rami of the upper four lumbar nerves. (c) The femoral nerve emerges from the lateral border of the psoas muscle. (d) The obturator nerve emerges from the medial border of the psoas muscle. (e) The iliohypogastric nerve emerges from the lateral border of the psoas muscle. View Answer8. B. The lumbar plexus is formed from the anterior rami of the upper four lumbar spinal nerves. 9. The following veins form important portal–systemic anastomoses except which? (a) Esophageal branches of the left gastric vein and tributaries of the azygos veins (b) Superior rectal vein and inferior vena cava (c) Paraumbilical veins and superficial veins of the anterior abdominal wall (d) Veins of the ascending and descending parts of the colon with the lumbar veins (e) Veins from the bare areas of the liver with the phrenic veins View Answer9. B. The superior rectal veins (tributaries of the portal vein) anastomose with the middle and inferior rectal veins (systemic tributaries). 10. The following statements concerning the ureters are correct except which? (a) Both ureters have three anatomic sites that are constricted. (b) Both ureters receive their blood supply from the testicular or ovarian arteries. (c) Both ureters are separated from the transverse processes of the lumbar vertebrae by the psoas muscles. (d) Both ureters pass anterior to the testicular or ovarian vessels. (e) Both ureters lie anterior to the sacroiliac joints. View Answer10. D. The ureters are crossed on their anterior surfaces by the testicular and ovarian vessels. 11. The following statements concerning the inferior mesenteric artery are correct except which? (a) The mesenteric artery’s colic branch supplies the descending colon. (b) The mesenteric artery gives off the inferior pancreaticoduodenal artery. (c) The mesenteric artery supplies the sigmoid colon. (d) The mesenteric artery’s branches contribute to the marginal artery. (e) The mesenteric artery arises from the aorta immediately below the third part of the duodenum. View Answer11. B. The inferior pancreaticoduodenal artery is a branch of the superior mesenteric artery. 12. The following structures are present within the lesser omentum except which? (a) The portal vein (b) The bile duct (c) The inferior vena cava (d) The hepatic artery (e) The lymph nodes View Answer12. C. The inferior vena cava lies on the posterior abdominal wall behind the parietal peritoneum. It is separated from the lesser omentum by the epiploic foramen. Matching Questions Match the numbered structures shown on the posteroanterior radiograph of the stomach and small intestine—after ingestion of a barium meal—with the appropriate lettered structures (38-year-old male).

13. Structure 1 14. Structure 2 15. Structure 3 16. Structure 4 17. Structure 5 (a) First part of duodenum (b) Second part of duodenum (c) Third part of duodenum (d) Air-filled fundus of stomach (e) Jejunum (f) Pylorus of stomach (g) None of the above View Answer13. B 14. F 15. D 16. G. The duodenojejunal junction 17. E Match the numbered structures shown on the posteroanterior radiograph of the large intestine—after evacuation of a barium enema—with the appropriate lettered lymphatic drainage (20-year-old female).

18. Structure 1 19. Structure 2 20. Structure 3 21. Structure 4 22. Structure 5 (a) Appendix (b) Splenic flexure (c) Transverse colon (d) Cecum (e) Rectum (f) Sigmoid colon (g) Descending colon (h) None of the above View Answer18. D 19. H. Right colic flexure 20. G 21. F 22. E Match the numbered structures shown on the intravenous pyelogram—obtained 20 minutes after injection of a suitable contrast medium—with the appropriate lettered structure (5-year-old female).

23. Structure 1 24. Structure 2 25. Structure 3 26. Structure 4 27. Structure 5 (a) Rectum (b) Pelvis of ureter (c) Sacrum (d) Ureter (e) Urinary bladder (f) Major calyx (g) None of the above View Answer23. G. Minor calyx 24. B 25. F 26. D 27. E Multiple-Choice Questions Read the case histories and select the best answer to the question following them. A mother took her 20-day-old baby boy to a pediatrician because he had started to vomit after his feeds. The baby was breast-fed. For the first 15 days after birth, the baby had taken his feeds very well and had slept contentedly in his crib following the normal after-feed burp. However, in the previous 5 days, the baby had begun to vomit toward the end of each feed, shooting the milk out of his mouth for a distance of 1 to 2 ft. After carefully questioning the mother and after a physical examination of the boy, the pediatrician made the diagnosis of congenital hypertrophic pyloric stenosis. 28. He was able to ascertain the following additional signs and symptoms except which? (a) Once the milk had been vomited, the child immediately would feed again, only to repeat the same performance. (b) On gentle palpation of the anterior abdominal wall, a small firm swelling was felt just below and medial to the tip of the left eighth costal cartilage. (c) On observing the anterior abdominal wall, an occasional wave of gastric peristalsis was seen traveling across the epigastrium from left to right. (d) The stools were small in quantity and infrequent. (e) The child showed signs of dehydration as evidenced by a depressed anterior fontanelle of the skull. View Answer28. B. In congenital hypertrophic pyloric stenosis, there is a localized muscular hypertrophy and hyperplasia of the pyloric sphincter, which is larger than normal and can usually be palpated just below and medial to the tip of the right ninth costal cartilage. A 6-year-old girl was examined by a pediatrician because she had a history of recurrent pain in the region of the umbilicus. The pain was dull and aching in nature and lasted for about 1 week. It had recurred on four occasions in the previous 2 years. Then, 2 days before the examination, the child had severe rectal bleeding and had fainted. 29. On examination of the child, the pediatrician found the following signs and symptoms consistent with the diagnosis of Meckel’s diverticulum except which? (a) Tenderness of the anterior abdominal wall in the right iliac region (b) Anemia (c) Stools streaked with dark red blood (d) Pyrexia of 102°F View Answer29. D. In many cases of Meckel’s diverticulum, a small area of ectopic gastric mucosa is present, which is capable of producing hydrochloric acid and pepsin. In the adjoining mucous membrane, this child had a chronic ulcer that was responsible for the umbilical pain. Sudden severe hemorrhage from an artery in the floor of the ulcer was the cause of the rectal bleeding and fainting attack. The condition is not associated with a pyrexia. After restoration of the blood volume and hemoglobin to a normal level, a child with this condition should be operated on and the diverticulum should be widely excised. The cut ends of the ileum then are joined by an end-to-end anastomosis. Footnote *For purposes of description, the hepatic artery is sometimes divided into the common hepatic artery, which extends from its origin to the gastroduodenal branch, and the hepatic artery proper, which is the remainder of the artery.

Leave a Reply


Time limit is exhausted. Please reload the CAPTCHA.

Categories

apply_now Pepperstone Group Limited