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Ovid: Oxford Handbook of Urology

Authors: Reynard, John; Brewster, Simon; Biers, Suzanne Title: Oxford Handbook of Urology, 1st Edition Copyright ©2006 Oxford University Press > Table of Contents > Chapter 8 – Miscellaneous urological disease of the kidney Chapter 8 Miscellaneous urological disease of the kidney P.326
Cystic renal disease: simple cysts Simple cysts are single or multiple renal ‘masses’ ranging from a few to many centimetres in diameter that do not communicate with any part of the nephron or the renal pelvis. They are mainly confined to the renal cortex, are filled with clear fluid, and contain a membrane composed of a single layer of flattened cuboidal epithelium. They can be unilateral or bilateral, and often affect the lower pole of the kidney. In comparison, parapelvic cysts are simple parenchymal cysts located adjacent to the renal pelvis or hilum. The prevalence of simple cysts increases with age. The precise prevalence depends on the method of diagnosis. On CT, 20% of adults have renal cysts by age 40 years and 30% by the age of 60. At postmortem, 50% of subjects aged >50 have simple cysts. Most reports show no gender predilection. Cysts do not usually increase in size with age, but may increase in number. Aetiology Both congenital and acquired causes have been suggested. Chronic dialysis is associated with the formation of new simple cysts. Presentation Simple cysts are most commonly diagnosed following a renal ultrasound or CT (less commonly, nowadays, after IVU) done for other purposes, and as such they represent an incidental finding. Very large cysts may present as an abdominal mass or cause dull flank or back pain. The great majority of simple renal cysts are asymptomatic. Acute, severe loin pain may follow bleeding into a cyst (causing sudden distension of the wall). Rupture (spontaneous or following renal trauma) is rare. Rupture into the pelvicalyceal system can produce haematuria. Infected cysts (rare) present with flank pain and fever. Very occasionally, large cysts can cause obstruction and hydronephrosis. Differential diagnosis

  • Renal cell carcinoma
  • Early autosomal dominant polycystic kidney disease (ADPKD)—diffuse, multiple, or bilateral cysts; presence of hepatic cysts
  • Complex renal cysts (i.e. those which contain blood, pus, or calcification)

Investigation Renal ultrasound Simple cysts are round or spherical, have a smooth and distinct outline, and are ‘anechoic’ (no echoes within the cyst—i.e. sound waves are transmitted through the cyst). Evidence of calcification, septation, irregular margins, or clusters of cysts requires further investigation (CT ± aspiration, MRI). In the absence of these features no further investigation is required. CT Simple cysts are seen as round, smooth-walled lesions with homogenous fluid in the cavity (with a typical density of -10 to +20 Hounsfield units), P.327
and with no enhancement after contrast (enhancement implies that the ‘mass’ contains vascular tissue or communicates with the collecting system—i.e. that it is not a simple cyst). Hyperdense cysts have a density of 20–90 Hounsfield units, do not enhance with contrast media, and are <3cm in diameter.

Table 8.1 Bosniak’s classification of CT appearance of simple and complex cysts
Type Description Approx. % of such cysts which are malignant* Treatment
I Simple benign cyst with no smooth margins, no contrast enhancement, no septation, no calcification None None; no follow-up required
II Smooth margins; thin septae; minimal calcification; no contrast enhancement Includes high-density (hyperdense) cysts 10% Observation—repeat ultrasound looking for increase in size or development of malignant features
III Irregular margins; moderate calcification; thick septation (septae >1mm thick) 40–50% Surgical exploration ± partial nephrectomy
IV Cystic malignant lesion; irregular margins and/or solid enhancing elements 90% Radical nephrectomy
* From Siegel et al. (1997) Study relating CTs of cysts where pathological identification had been performed. Am J Roentgenol 169:813–18.

Treatment A simple cyst (round or spherical, smooth wall, distinct outline, and no internal echoes) requires no further investigation, no treatment, and no follow-up. In the rare situation where the cyst is thought to be the cause of symptoms (e.g. back or flank pain) treatment options include percutaneous aspiration ± injection of sclerosing agent or surgical excision of the cyst wall. In the rare event of cyst infection, percutaneous drainage and antibiotics are indicated. Cysts with features on ultrasound suggesting possible malignancy (calcification, septation, irregular margins) should be investigated by CT with contrast. P.328
Cystic renal disease: calyceal diverticulum A calyceal diverticulum is an outpocketing from the pelvicalyceal system, with which it communicates by way of a narrow neck. It is lined by a smooth layer of transitional epithelium and is covered by a thin layer of renal cortex. The aetiology of calyceal diverticula is unknown. They are usually asymptomatic and are discovered incidentally on an IVU. Symptoms may result from the development of a stone or infection within the diverticulum, presumably caused by urinary stasis. Stones which form within the calyceal diverticulum may be treated by flexible ureteroscopy and laser lithotripsy or, if large, by PCNL (if percutaneous access is possible). ESWL may result in stone fragmentation, but it may be difficult for the stone fragments to get out of the diverticulum and they may simply reform into a larger stone. Endoscopic dilatation or incision of the neck of the diverticulum may be attempted at the time of stone surgery to prevent recurrence, and this technique can also be employed if the diverticulum is thought to be the cause of recurrent urinary infection. Open surgery has been used to remove stones and to de-roof calyceal diverticula. P.329
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Cystic renal disease: medullary sponge kidney (MSK) Definition A cystic condition of the kidneys characterized by dilatation of the distal collecting ducts associated with the formation of multiple cysts and diverticula within the medulla of the kidney. Prevalence Difficult to know as it may be asymptomatic (diagnosed on an IVU done for other reasons or at postmortem). Estimated to affect between 1 in 5000 to 1 in 20,000 people in the general population; 1 in 200 in those undergoing IVU (a select population). In 75% of cases both kidneys are affected. Pathology The renal medulla resembles a sponge in cross-section due to dilated collecting ducts in the renal papillae and the development of numerous small cysts. This is associated with urinary stasis and the formation of small calculi within the cysts. It has a reported familial inheritance and is associated with other malformations (hemihypertrophy). Presentation The majority of patients are asymptomatic. When symptoms do occur, they include ureteric colic, renal stone disease (calcium oxalate ± calcium phosphate), UTI, and haematuria (microscopic or macroscopic). Up to 50% have hypercalciuria due to renal calcium leak or increased gastrointestinal calcium absorption. Renal function is normal, unless obstruction occurs (secondary to renal pelvis or ureteric stones). Differential diagnosis Other causes of nephrocalcinosis (deposition of calcium in the renal medulla) (e.g. TB, healed papillary necrosis). Investigation Intravenous urogram (IVU) The characteristic radiological features of MSK, as seen on IVU, are dilatation of the distal portion of the collecting ducts with numerous associated cysts and diverticula (the dilated ducts are said to give the appearance of ‘bristles on a brush’). The collecting ducts may become filled with calcifications, giving an appearance described as a ‘bouquet of flowers’ or ‘bunches of grapes’. Biochemistry 24-h urinary calcium may be elevated (hypercalciuria). Detection of hypercalciuria requires further investigation to exclude other causes (i.e. raised serum parathyroid hormone levels (PTH) indicate hyperparathyroidism). P.331
Treatment Asymptomatic MSK disease requires no treatment. General measures to reduce urine calcium levels help reduce the chance of calcium stone formation (high fluid intake, vegetarian diet, low salt intake, consumption of fruit and citrus fruit juices). Thiazide diuretics may be required for hypercalciuria resistant to dietary measures designed to lower urine calcium concentration. Intra-renal calculi are often small and, as such, may not require treatment, but if indicated this can take the form of ESWL or flexible ureteroscopy and laser treatment. Ureteric stones are again usually small and will therefore pass spontaneously in many cases, with a period of observation. Renal function tends to remain stable in the long term. P.332
Acquired renal cystic disease (ARCD) Cystic degenerative disease of the kidney with ≥5 cysts visualized on CT scan. By definition this is an acquired condition, as opposed to adult polycystic kidney disease (ADPKD) which is inherited (in an autosomal dominant fashion). It is predominantly associated with chronic and end-stage renal failure (originally, it was thought to specifically affect patients on haemodialysis). Clinically important because it may cause pain or haematuria and is associated with the development of benign and malignant renal tumours. ~one third of patients develop ARCD after 3 years of dialysis. Male:female ratio is 2:1. Pathology Usually multiple, bilateral cysts found mainly within the cortex of small, contracted kidneys. Cysts vary in size (average 0.5–1cm) and are filled with a clear fluid, which may contain oxalate crystals. They usually have cuboidal and columnar epithelial linings, and are in continuity with renal tubules (and therefore cannot be defined as simple cysts). Atypical cysts have a hyperplastic lining of epithelial cells, which may represent a precursor for tumour formation. Renal transplantation can cause regression of cysts in the native kidneys. Aetiology The exact pathogenesis is unknown, but several theories have been proposed. Obstruction or ischaemia of renal tubules may induce cyst formation. Renal failure may predispose to the accumulation of toxic endogenous substances or metabolites, alter the release of growth factors and result in changes in sex steroid production, or cause cell proliferation (secondary to immunosuppressive effects) which result in cyst formation. Associated disorders There is an increased risk of benign and malignant renal tumours. The chance of developing renal cell carcinoma is 3–6 times greater than the general population (males > females). ARCD may also be associated with tubulo-interstitial nephritis and membranoproliferative glomerulonephritis. Presentation Flank pain; UTI; macroscopic haematuria; renal colic (stone disease); hypertension. Investigation This depends on the presenting symptoms.

  • For suspected UTI—culture urine.
  • For haematuria—urine cytology, flexible cystoscopy, and renal ultrasound. On ultrasound the kidneys are small and hyperechoic, with multiple cysts of varying size, many of which show calcification. If the nature of the cysts cannot be determined with certainty on ultrasound, arrange a renal CT.

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Treatment Persistent macroscopic haematuria can become problematic, exacerbated by heparinization (required for haemodialysis). Options include transferring to peritoneal dialysis, renal embolisation, or nephrectomy. Infected cysts which develop into abscesses require percutaneous or surgical drainage. Radical nephrectomy is indicated for renal masses with features suspicious of malignancy. Smaller asymptomatic masses require surveillance. P.334
Autosomal dominant (adult) polycystic kidney disease (ADPKD) Definition Autosomal dominant inherited disorder leading to the development of multiple expanding renal parenchymal cysts. Epidemiology Incidence is 0.1%; 95% are bilateral. Symptoms manifest in the 4th decade. ADPKD accounts for 10% of all cases of renal failure. Pathology The kidneys reach an enormous size due to multiple fluid-filled cysts and can easily be palpated on abdominal examination. Expansion of the cysts results in ischaemic atrophy of the surrounding renal parenchyma, and obstruction of normal renal tubules. End-stage renal failure is inevitable and occurs around the age of 50 yrs. Associated disorders 10–30% incidence of Circle of Willis berry aneurysms (associated with subarachnoid haemorrhage); cysts of the liver (33%), pancreas (10%), and spleen (<5%); renal adenoma; cardiac valve abnormalities; aortic aneurysms and diverticular disease. Aetiology PKD-1 gene defects (chromosome 16) account for 90% of cases; PKD-2 gene defects (chromosome 4) cause 10%, and now a third gene, PKD-3 is also implicated. Pathogenesis theories include intrinsic basement membrane abnormalities; tubular epithelial hyperplasia (causing tubular obstruction and basement membrane weakness), and alterations in the supportive extracellular matrix due to defective proteins, all of which may cause cyst formation. Presentation Positive family history (50% inheritance); palpable abdominal masses; flank pain (due to mass effect, infection, stones, or following acute cystic distension due to haemorrhage or obstruction); macroscopic (and microscopic) haematuria; UTI; and hypertension (75%). Renal failure may present with lethargy, nausea, vomiting, anaemia, confusion, and seizures. Differential diagnosis Renal tumours; simple cysts; von Hippel–Landau syndrome (cerebellar and retinal haemangioblastomas; renal, adrenal, and pancreatic cysts); tuberous sclerosis (adenoma sebaceum, epilepsy, learning difficulties, with polycystic kidneys and renal tumours). Investigation This depends on the presenting symptoms.

  • For suspected UTI—culture urine.
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  • For haematuria—urine cytology, flexible cystoscopy, and renal ultrasound. On ultrasound the kidneys are small and hyperechoic, with multiple cysts of varying size, many of which show calcification. If the nature of the cysts cannot be determined with certainty on ultrasound, arrange a renal CT.
  • Renal failure will be managed by a nephrologist. Anaemia may occur, though ADPKD may cause increased erythropoietin production and polycythaemia.
  • Renal imaging (ultrasound and CT are useful for investigation of complications).

Treatment The aim is to preserve renal function as long as possible (control hypertension and UTI). Infected cysts (abscesses) should be drained. Persistent, heavy haematuria can be controlled by embolisation or nephrectomy. Progressive renal failure requires dialysis and, ultimately, renal transplantation. P.336
Vesicoureteric reflux (VUR) in adults VUR is the retrograde flow of urine from the bladder into the upper urinary tract with or without dilatation of the ureter, renal pelvis, and calyces. It can cause symptoms and may lead to renal failure (reflux nephropathy). In the UK, 25% of patients requiring haemodialysis or transplantation do so because of reflux nephropathy. Pathophysiology Reflux is normally prevented by low bladder pressures, efficient ureteric peristalsis, and the ability of the vesicoureteric junction (VUJ) to occlude the distal ureter during bladder contraction. This is assisted by the ureters passing obliquely through the bladder wall (the ‘intramural’ ureter), which is 1–2cm long. Normal intramural ureteric length to ureteric diameter ratio is 5:1. VUR of childhood tends to resolve spontaneously with increasing age because as the bladder grows, the intramural ureter lengthens. Classification Primary: a primary anatomical (and therefore functional) defect where the intramural length of the ureter is too short (ratio <5:1). Secondary to some other anatomical or functional problem:

  • Bladder outlet obstruction (BPO, DSD due to neuropathic disorders,1 posterior urethral valves, urethral stricture) which leads to elevated bladder pressures.
  • Poor bladder compliance or the intermittently elevated pressures of detrusor hyperreflexia (due to neuropathic disorders1—e.g. spinal cord injury, spina bifida).
  • Iatrogenic reflux following TURP or TURBT (a tumour overlying the ureteric orifice)—this is rare; ureteric meatotomy (incision of the ureteric orifice) for removal of ureteric stones at the VUJ; following incision of a ureterocele; ureteroneocystostomy; post pelvic radiotherapy.
  • Inflammatory conditions affecting function of the VUJ: TB, schistosomiasis, UTI.

Associated disorders VUR is commonly seen in duplex ureters (the Meyer–Weigert law).2 Cystitis can cause VUR through bladder inflammation, reduced bladder compliance, increased pressures, and distortion of the VUJ. Coexistence of UTI with VUR is a potent cause of pyelonephritis—reflux of infected urine under high pressure causes reflux nephropathy, resulting in renal scarring, hypertension, and renal impairment. P.337
Presentation

  • VUR may be symptomless, being identified during VCUG, IVU, or renal ultrasound (which shows ureteric and renal pelvis dilatation) done for some other cause.
  • UTI symptoms.
  • Loin pain associated with a full bladder or immediately after micturition.

Symptoms of recurrent UTI or of loin pain may have been present for many years before the patient seeks medical advice. Even then it may take some time for a diagnosis of VUR to be made because a high index of suspicion is required and the definitive test for making a diagnosis of VUR (VCUG—see below) is invasive (although VUR may be diagnosed by the less invasive use of IVU). Investigation The definitive test for the diagnosis of VUR is cystography. VUR may be apparent during bladder filling or during voiding (voiding cystourethrography, VCUG—also known as micturating cystourethrography, MCUG). Urodynamics establishes the presence of voiding dysfunction (e.g. DSD) if this is suspected from the clinical picture. If there is radiographic evidence of reflux nephropathy check blood pressure, check the urine for proteinuria, measure serum creatinine, and arrange a 99mTc-DMSA isotope study to assess renal cortical scarring and determine split renal function. Management VUR is harmful to the kidney:

  • In the presence of infected urine
  • Where bladder pressures are markedly elevated (due to severe BOO, poor compliance, or high-pressure hyperreflexic bladder contractions)

In the absence of urinary infection or severe outflow obstruction/raised bladder pressures, VUR is not harmful, at least in the short term (months). Subsequent management depends on:

  • The presence and severity of symptoms
  • The presence of recurrent, bacteriologically proven urinary infection
  • The presence of already established renal damage (radiological evid-ence of reflux nephropathy, hypertension, proteinuria—proteinuria is a poor prognostic factor in patients with VUR, indicating the likelihood of impending ESRF)

For the patient with primary VUR, recurrent UTIs with no symptoms between infections, no hypertension, and good renal function: treat the UTIs when they occur; consider low-dose antibiotic prophylaxis if UTIs occur frequently (say >3 per year). If the UTIs are regularly associated with constitutional disturbance (acute pyelonephritis rather than simple cystitis), then ureteric reimplantation is indicated. For the patient with primary VUR and objective evidence of deterioration in the affected kidney (i.e. progressive radiological signs of reflux nephropathy or reduction in renal function): ureteric reimplantation. P.338
Reflux into a non-functioning kidney (<10% function on DMSA scan) with recurrent UTIs and/or hypertension: nephroureterectomy. Primary reflux with severe recurrent loin pain: ureteric reimplantation. Secondary reflux:

  • into a transplanted kidney: no treatment is necessary.
  • VUR in association with the neuropathic bladder: treat the underlying cause—relieve BOO, improve bladder compliance (options: intravesical Botox injections, augmentation cystoplasty, sacral deafferentation).

VUR with no symptoms, no UTI, no high bladder pressures and no BOO: the management of these patients is controversial because it is not known whether low-pressure, sterile reflux causes deterioration in renal function over many years without treatment. For grade I and II reflux (reflux of contrast into non-dilated ureter), it probably doesn’t, and many urologists would not recommend surgery, but would monitor the patient for infection, hypertension, and evidence of deterioration in the appearance and function of the kidneys. For grade III or more it may do so, and many urologists would recommend ureteric reimplantation (or a STING procedure) (see Fig. 8.1 for grading.).

Fig. 8.1 International reflux classification

Footnotes 1 Neuropathic disorders therefore cause VUR because they lead to intermittently or chronically raised bladder pressure (due to BOO, poor compliance, and/or detrusor hyperreflexia). 2 The lower pole ureter inserts into the bladder in a proximal location to the upper pole ureter, which inserts distally—i.e. nearer the bladder neck. The lower pole ureter has a shorter intramural length and therefore refluxes. The upper pole ureter has a longer intramural length and tends to be obstructed. P.339
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Pelviureteric junction (PUJ) obstruction in adults Definition An obstruction of the proximal ureter at the junction with the renal pelvis resulting in a restriction of urine flow. Known as ‘ureteropelvic junction obstruction’ in North America (UPJO). Epidemiology Males > females (5:2 ratio). In unilateral cases, the left side is affected more often than the right. 10–15% are bilateral. Aetiology Congenital

  • Intrinsic: smooth muscle defect results in an aperistaltic segment of ureter at the PUJ.
  • Extrinsic: compression from lower renal pole vessel over which the PUJ runs. It is unlikely that these vessels are the primary cause of the obstruction. It is more probable that PUJO leads to a dilated PUJ and ballooning of the renal pelvis over the lower pole vessels, which may thus contribute to, but is not the primary cause of the obstruction.

Acquired PUJ stricture secondary to ureteral manipulation (e.g. ureteroscopy); trauma from passage of calculi; fibroepithelial polyps; TCC of urothelium at PUJ; external compression of ureter by retroperitoneal fibrosis or malignancy. Presentation Flank pain precipitated by a diuresis (high fluid intake; especially precipitated by consumption of alcohol); flank mass; UTI; haematuria (after minor trauma). It may also be associated with vesicoureteric reflux (VUR). Investigation Renal ultrasound shows renal pelvis dilatation in the absence of a dilated ureter. IVU demonstrates delay of excretion of contrast and a dilated pelvicalyceal system. Arrange a CT to exclude a small, radiolucent stone, urothelial TCC, or retroperitoneal pathology which may be the cause of the obstruction at the PUJ. MAG3 renography with administration of frusemide to establish a maximum diuresis is the definitive diagnostic test for PUJO. Radioisotope accumulates in the renal pelvis, and following iv frusemide it continues to accumulate (a ‘rising’ curve). Many urologists perform retrograde pyelography to establish the exact site of the obstruction, but they do this at the time of PUJ repair to avoid introducing infection into an obstructed renal pelvis. Treatment Surgery Surgery is indicated for recurrent episodes of bothersome pain, renal impairment, where a stone has developed in the obstructed kidney, and where infection (pyonephrosis) has supervened. In the absence of symptoms, consider watchful waiting with serial MAG3 renograms. If renal function remains stable and the patient remains free of symptoms, there is no need to operate. P.341
Endoscopic treatment of a PUJO is called an endopyelotomy (or pyelolysis). Various techniques have been described, but the essential principle is the same—full-thickness incision through the obstructing proximal ureter, from within the lumen of the ureter down into the peripelvic and periureteral fat, using a sharp knife or Holmium:YAG laser. The incision is stented for 4 weeks to allow re-epithelialization of the PUJ. Relatively minimally invasive. Generally not used for PUJO >2cm in length. The incision may be made percutaneously or by a retrograde approach via a rigid or flexible ureteroscope, or by using a specially designed endoplyelotomy balloon (the Acucise® technique).3 The presence of a combination of PUJO and a renal stone that is suitable for PCNL is an indication for combined PCNL and percutaneous endopyelotomy. Success rates in terms of relieving obstruction: percutaneous endopyelotomy range from 60–100% (mean 70%); cautery wire balloon endopyelotomy 70%; ureteroscopic endopyelotomy 80%. Pyeloplasty

  • Open: has success rates of 95%, and may also be used after endopyelotomy failure or as a first line technique.
  • Laparoscopic pyeloplasty has the advantage of accelerated patient recovery.
  • Common techniques include dismembered pyeloplasty (also known as the Anderson–Hynes pyeloplasty: the narrowed area of PUJ is excised, the proximal ureter is spatulated and anastomosed to the renal pelvis), flap pyeloplasty (Culp), and Y-V-plasty (Foley).

Footnote 3 An angioplasty-type balloon over which runs a cautery wire is inflated across the PUJ. Passage of an electrical current heats the wire and this cuts through the obstructing ring of tissue at the PUJ. P.342
Anomalies of renal ascent and fusion: horseshoe kidney, pelvic kidney, malrotation Abnormalities of renal ascent and fusion occur in weeks 6–9 of gestation, when the embryonic kidney is ‘ascending’ to its definitive lumbar position (‘ascending’ as a result of rapid caudal growth of the embryo). Horseshoe kidney Most common example of renal fusion. Prevalence 1 in 400. Male to female ratio 2:1. The kidneys lie vertically (instead of obliquely) and are joined at their lower poles (in 95%) by midline parenchymal tissue (the isthmus). The inferior mesenteric artery obstructs ascent of the isthmus. Consequently, the horseshoe kidney lies lower in the abdomen (L3 or L4 vertebral level). Normal rotation of the kidney is also prevented and therefore the renal pelvis lies anteriorly, with the ureters also passing anteriorly over the kidneys and isthmus (but entering the bladder normally). Blood supply is variable, usually from one or more renal arteries or their branches, or from branches off the aorta or inferior mesenteric artery (see Fig. 8.2). A proportion of individuals with horseshoe kidneys have associated congenital abnormalities (Turner’s syndrome, trisomy 18, genitourinary anomalies, ureteric duplication); vesicoureteric reflux; PUJ obstruction; and renal tumours (including Wilms’ tumours). Most patients with horseshoe kidneys remain asymptomatic; however, infection and calculi may develop and cause symptoms. The diagnosis is usually suggested on renal ultrasound and confirmed by IVU (calyces of the lower renal pole are seen to point medially, and lie medially in relation to the ureters) or CT. Renal function is usually normal. Pelvic kidney This represents a form of renal ectopia. Prevalence 1 in 2000–3000, with both sexes affected equally. The left kidney is affected more often than the right, and bilateral cases are seen in <10%. The affected kidney is smaller, with the renal pelvis positioned anteriorly (instead of medially), and the ureter is short, but enters the bladder normally. Pelvic kidneys lie opposite the sacrum and below the aortic bifurcation, and are supplied by adjacent (aberrant) vessels (see Fig. 8.3). There is an increased risk of congenital anomalies including contralateral renal agenesis and genital malformations. Most are asymptomatic. Diagnosis is made on renal ultrasound scan, IVU, or renography. Complications include obstruction, hydronephrosis, and infection.

Fig. 8.2 Horseshoe kidney
Fig. 8.3 Pelvic (ectopic) kidney

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Malrotation The kidney is located in a normal position, but the renal pelvis fails to rotate from an anterior to a medial orientation. Prevalence is ~1 in 1000, with a male to female ratio of 2:1. The renal shape may be altered (flattened, oval, triangular, or elongated) and the kidney retains its fetal lobulated outline. (See Fig. 8.4) It is associated with increased deposition of fibrous tissue around the renal hilum, which can produce symptoms due to ureteric or PUJ obstruction (causing hydronephrosis, infection, or stone formation). Most patients, however, remain asymptomatic. The diagnosis is made on renal ultrasound scan, IVU, or retrograde pyelography.

Fig. 8.4 Malrotation of the kidney

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Renal duplications Definitions A duplex kidney has an upper pole and a lower pole, each with its own separate pelvicalyceal system and ureter. The two ureters may join to form a single ureter at the pelviureteric junction (bifid system) or more distally (bifid ureter) before entering the bladder through one ureteric orifice. Alternatively, the two ureters may pass down individually to the bladder (complete duplication). In this case, the Weigert-Meyer rule states that the upper pole ureter always opens onto the bladder medially and inferiorly to the ureter of the lower pole, thereby predisposing to ectopic placement of the ureteric orifice and obstruction (due to the longer intramural course of the ureter through the bladder wall). The lower pole ureter opens onto the bladder laterally and superiorly, reducing the intramural ureteric length, which predisposes to vesicoureteric reflux (in up to 85%). Epidemiology Ureteric duplication occurs in 1 in 125 individuals. Female to male ratio is 2:1. Unilateral cases are more common than bilateral, with right and left sides affected equally. Risk of other congenital malformations is increased. Embryology In duplication, two ureteric buds arise from the mesonephric duct (week 4 gestation). The ureteric bud situated more distally (lower pole ureter) enters the bladder first, and so migrates a longer distance, resulting in the superior and lateral position of the ureteric orifice. The proximal bud (upper pole ureter) has less time to migrate, and consequently the ureteric orifice is inferior and medial (ectopic). Interaction of each ureteric bud with the same metanephric tissue creates separate collecting systems within the same renal unit. With bifid ureters, a single ureteric bud splits after it has emerged from the mesonephric duct. Complications Ectopic ureters are associated with both upper renal pole hydronephrosis (secondary to obstruction) and hypoplasia or dysplasia (renal maldevelopment related to ectopic displacement of ureteric orifice). Lower pole ureters are prone to reflux, resulting in hydroureter and hydronephrosis. Bifid ureters can get urine continuously passing from one collecting system to the other, causing urinary stasis (predisposing to infection). Presentation Symptoms of UTI, flank pain, or incidental finding. P.347
Investigation

  • Renal ultrasound scan demonstrates ureteric duplication ± dilatation and hydronephrosis.
  • IVU decreased contrast excretion from renal upper pole ± hydronephrosis (which may displace the lower pole downwards and outwards producing a ‘drooping lily’ appearance).
  • Micturating cystourethrography (MCUG) will determine whether reflux is present.
  • CT and MRI reveals detailed anatomical information.
  • Isotope renogram (99mTc-DMSA) assesses renal function.

Treatment In symptomatic patients, the aim is to reduce obstruction and reflux, and improve function. Common shealth ureteric reimplantation (where a cuff of bladder tissue is taken that encompasses both duplicated ureters) can treat both conditions. Where an ectopic ureter is associated with a poorly functioning renal upper pole, open or laparoscopic heminephrectomy with excision of the associated ureter may be considered.

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