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//VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

Splenic artery

The spleen is supplied exclusively from the splenic artery (see Fig. 70.7). This is the largest branch of the coeliac axis and its course is among the most tortuous in the body. From its origin the artery runs a little way inferiorly, then turns rapidly to the left to run initially horizontally above the level of the neck of the pancreas, before ascending as it passes more laterally. It is less steeply inclined than the body and tail of the pancreas and so comes to lie posterior to the superior border of the gland. It lies in multiple loops or even coils which appear above the superior border of the pancreas and descend to lie behind the gland. The splenic artery lies anterior to the left kidney and left suprarenal gland and runs in the splenorenal ligament posterior to the tail of the pancreas. It divides into two or three main branches before entering the hilum of the spleen (Fig. 71.1). As these branches enter the hilum they divide further into four or five segmental arteries that each supply a segment of the splenic tissue. There is relatively little arterial collateral circulation between the segments, which means that occlusion of a segmental vessel often leads to infarction of part of the spleen. There is, however, considerable venous collateral circulation between the segments, making segmental resection of the spleen practically impossible. The splenic artery gives off various branches to the pancreas in its course and gives off short gastric arteries to the stomach just prior to dividing or from its terminal branches.

Splenic vein

The splenic vein is formed within the splenorenal ligament, close to the tip of the tail of the pancreas, by five or six tributaries that emerge from the hilum of the spleen (Fig. 71.4). The tributaries are thin walled and often spread over several centimetres because the hilum is long and thin (Fig. 71.1). This must be remembered during surgical removal of the spleen because the venous tributaries must be divided close to the hilum to avoid injury to the pancreatic tail. They should be ligated in several groups to prevent the risk of avulsion of the veins from the splenic hilum and consequent profuse bleeding before the resection is complete.

  

Fig. 71.4  Axial oblique CT slice of the portal vein and splenic vein.

The splenic vein runs in the splenorenal ligament below the splenic artery and posterior to the tail of the pancreas. It descends to the right, and crosses the posterior abdominal wall inferior to the splenic artery and posterior to the body of the pancreas, receiving numerous short tributaries from the gland as it does so. It crosses anterior to the left kidney and renal hilum and is separated from the left sympathetic trunk and left crus of the diaphragm by the left renal vessels, and from the abdominal aorta by the superior mesenteric artery and left renal vein. It ends behind the neck of the pancreas, where it joins the superior mesenteric vein to form the portal vein. The short gastric and left gastro-epiploic veins drain into the splenic vein through the folds of the gastrosplenic ligament near its origin.

Lymphatics

Lymphatic vessels drain along the splenic trabeculae and pass out of the hilum into lymphatic vessels that accompany the splenic artery and vein. They run posterior to the pancreas, close to the splenic artery, and drain into nodes at the hilum and along the splenic artery and into the coeliac nodes.

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