Congenital ureteric anomalies can be generally subdivided into those of ureteric number, direction, diameter and filling defects.⁸ The most common ureteric anomaly is that of ureteric number, which was observed in 0.7% of autopsies in one series.⁹ The renal parenchyma may be divided into upper and lower components by a septum of Bertin. This anomaly is associated with a bifid collecting system consisting of two pelvices joined proximal to the ureteropelvic junction (Fig. 35-10). The upper calyces drain into the upper pelvis, while the mid and lower calyces drain into the lower pelvis. The ureters may also join distal to the ureteropelvic junction (Fig. 35-11) with a Y-configuration. This is normally asymptomatic unless urine refluxes from one ureter up the other causing ureteroureteric reflux, also termed yo-yo reflux, which should be considered if one ureteric segment is disproportionately enlarged.¹⁰ This anomaly can precipitate recurrent infections and obstruction of a ureteric segment.

When there is complete duplication of the renal collecting system, the ureter draining the upper moiety tends to insert ectopically below and medial to the normal ureteric orifice or sometimes outside the bladder (extravesical). The ureter draining the upper moiety tends to drain ectopically due to delayed separation of the ureteric bud from its parent Wolffian duct, which migrates in a caudal direction during development.¹¹ For this reason it is suggested that if the upper urinary tract is normal, the ureter is likely to have an orthopic insertion; however, a dysplastic or malfunctioning upper tract is likely associated with an ectopic insertion. The ectopic ureter often has a strictured distal element which causes proximal dilatation in the bladder wall and ureterocele formation in 75% of affected patients and is eight times more common in women than men (Fig. 35-12).¹⁰ A ureterocele contains layers of ureteric and bladder epithelium which are optimally appreciated on early imaging on a voiding cystourethrogram (VCUG) but can be obscured by contrast medium, effaced or everted similar to a diverticulum when the bladder is full (Fig. 35-13).¹² A cobra-neck appearance is observed at intravenous urography (IVU) consisting of a dilated contrast-filled ureter surrounded by thin rim of ureteric wall and bladder mucosa measuring less than 2 mm in diameter (Fig. 35-14). Ectopic ureteroceles often project into the bladder and are associated with recurrent infection, stone formation, complete ipsilateral or bilateral ureteric obstruction. Orthopic ureteric insertion in the setting of ureteric duplication is generally asymptomatic unless larger than 2 cm. An ectopic ureter with extravesical insertion below the bladder neck, into the urethra or vagina, can cause urinary incontinence, infection and ureteric obstruction from fibrotic stricture formation. The ectopic ureter generally inserts above the external sphincter in men, thereby inhibiting incontinence but in about 50% of women this does not occur and patients present with dribbling incontinence but are able to void normally.

The ureter draining the lower moiety of a duplicated collecting system inserts orthopically but tends to reflux. In fact, reflux is the most common association of ureteric duplication. Lower pole hydronephrosis in the setting of duplication is mainly due to reflux rather than an obstructing ureterocele or stricture. In duplicated systems the dilated upper pole ureter can impinge and displace the lower pole ureter, which can be appreciated on voiding cystourethrogram. Conformity of a duplicated collecting system with this pattern of ureteric insertion is known as the Weigert–Meyer Rule.¹⁰ Approximately one-third of patients with complete ureteric duplication have an additional congenital anomaly such as horseshoe kidney and multicystic dysplastic kidney.

Anomalies of ureteric course generally occur due to extrinsic processes, which push or pull complete or segmental portions of the ureter in medial or lateral directions. Potential causes of medial ureteric deviation include retrocaval ureter (Fig. 35-15), laterally based renal, retroperitoneal, lymph node, central pelvic or psoas masses, pelvic lipomatosis, vascular aneurysms or haematoma, retroperitoneal fibrosis and surgical resection of pelvic organs such as the entire rectum. Lateral ureteric deviation is caused by retroperitoneal and central pelvic masses such as lymphadenopathy (testicular metastases), aortic aneurysm, psoas enlargement (young men) and abnormal renal position (malrotated or horseshoe kidney). Cross-sectional imaging is usually required to confirm aetiology. Acute medial deviation of the right ureter medial to corresponding vertebral pedicles on an abdominal radiograph is virtually diagnostic of retrocaval ureter. Pelvic lipomatosis pushes the distal ureters medially. This condition is more common in African-American men and can induce bilateral hydronephrosis. A characteristic pear-shaped bladder may be observed and cystitis glandularis of the bladder is an associated premalignant condition. Retroperitoneal fibrosis pulls one or both ureters medially in about half of cases. Psoas muscle hypertrophy can be recognised as the cause of lateral ureteric deviation if the lateral psoas border exceeds 8 cm from the lateral edge of the corresponding vertebral body at the level of the iliac crest.

Other congenital ureteric anomalies of note include ureteric stricture, megaureter and vesicoureteric reflux. Ureteric strictures are the most common of these anomalies. The ureteropelvic junction, in particular, and the ureterovesical junction to a lesser extent, are predisposed to stricture formation. Ischaemia during development is thought to incite fibrosis and stricture formation in these regions. There is consequent dilatation of the proximal ureter and possibly the renal pelvis, which may be detected by screening or as an incidental finding in asymptomatic patients, or associated with flank pain, recurrent infection, haematuria or stone formation, anywhere from in utero to adulthood (Fig. 35-16). Ureteric strictures may also be caused by a vessel crossing from medial to lateral with a convex lateral margin in about 1 in 20 cases of ureteropelvic junction obstruction (Fig. 35-17).

Ureteric diameter exceeding 7 mm is termed mega­ureter.¹³ Megaureter may be a congenital phenomenon or secondary to a process in the bladder or urethra (Fig. 35-18). Primary megaureter is due to deficient ureteric musculature, which limits peristalsis and leads to upstream dilatation. Three forms are described: obstructing primary megaureter, refluxing primary megaureter, and non-obstructing non-refluxing primary megaureter. Primary refluxing megaureter is due to inadequate one-way valve mechanism at the vesicoureteric junction. In non-obstructing non-refluxing primary megaureter the calyces should maintain a crisp outline and not be blunted as with primary obstructing megaureter and there should be normal excretion (Fig. 35-19). Three-quarters of cases are unilateral; there is left-sided a male predominance.

Vesicoureteric reflux is caused by maldevelopment of the distal ureter characterised by a shortened intramucosal bladder tract with a deficient valve-like mechanism. Reflux increases the risks of renal infection, scarring and reflux nephropathy. Vesicoureteric reflux represents the most common cause of antenatal hydronephrosis, responsible for 40% of cases.¹⁴ Grading is between 1 and 5 according to the International Reflux Study Committee as determined by the most severe degree of reflux at voiding cystourethrography: reflux into the ureter only (I), to the renal pelvis without calyceal dilatation (II), with mild or moderate ureteric and calyceal dilatation but preserves fornices (III), and severe ureteric and calyceal dilatation with obliteration of forniceal angles but maintained greater calyceal papillary impressions (IV), and finally gross dilatation with effacement of the papillary impressions (V).¹⁵

Bladder and Urethra

The term cloaca is derived from the Latin term for sewer. Cloacal malformation is believed to occur when the urorectal septum fails to separate the cloaca and results in a shared orifice for the genital, urinary and lower gastrointestinal tracts in a phenotypic female. A urogenital sinus anomaly occurs at a later stage in development and results in a common drainage tract for the genital and urinary systems. Extrophy of the cloaca occurs in males and females when there is failed closure of the infra-umbilical anterior abdominal wall, creating a defect larger than that observed with bladder extrophy.

Several anomalies of bladder development may occur, including agenesis, duplication, diverticula, prune-belly syndrome and anomalies of the cloaca. Agenesis of the bladder is very rare and its origin is uncertain, but since the hindgut often develops normally, maldevelopment of the anterior cloaca is usually responsible. The ureters insert ectopically in this situation and further urinary tract anomalies are common. Rarely, there may be duplication of the bladder and urethra created by a septum containing detrusor muscle. This occurs more commonly in a sagittal rather than in a coronal plane. This anomaly is associated with uni- or bilateral renal obstruction, single or duplicated urethras, genital or lower gastrointestinal tract duplication.

Bladder diverticula in children in the absence of obstruction have an incidence of 1.7%.¹⁶ A diverticulum at the vesicoureteric junction is known as a Hutch diverticulum and is associated with vesicoureteric reflux (Fig. 35-20). The term bladder ear, on the other hand, refers to a diverticulum which descends into the internal inguinal ring (Fig. 35-21). Congenital diverticula are often asymptomatic; however, infection, stone formation and possibly cancer can occur, so surgical repair is sometimes necessary. Prune-belly syndrome, also known as Eagle–Barrett syndrome, is a rare constellation of findings consisting of absent rectus abdominis muscles with lax abdominal wall skin, bilateral undescended testes, dilated ureters and prostatic urethra and abnormal kidneys.² Vesicoureteric reflux is a common association and affected neonates generally die early. The bladder wall is characteristically thickened and the bladder enlarged though not trabeculated, owing to increased mural connective tissue. Associated anomalies are common, including those of the musculoskeletal, cardio­respiratory or gastrointestinal systems. The urachus is often patent in the setting of prune-belly syndrome.

Failure of the urachus to fibrose and obliterate causes a constellation of anomalies. Patent urachus presents with urine draining from the umbilicus at birth. Urachal cysts occur when the umbilical and vesical portions are occluded but a central segment remains patent. A urachal sinus forms when there is a blind-ending tract within the urachus contiguous with the umbilical opening, or a urachal diverticulum is observed when a segment of urachus remains in continuity with the bladder.¹⁷ Infection is the most common complication affecting urachal remnants. Adenocarcinoma of urachal remnant is a rare cancer that often produces mucin and may contain calcification. Prognosis is typically worse compared with bladder malignancies.

Posterior urethral valves are the most common malformation of the urethra. The valve is created from a remnant of the Wolffian duct and consists of a raised mucosal fold which courses obliquely from the verumontanum to the inferior aspect of the prostatic urethra (Fig. 35-22). Diagnosis is often made after bilateral hydro­nephrosis is detected. Bladder outflow obstruction raises intravesical pressure, causes bladder wall thickening, trabeculation, and vesicoureteric reflux in approximately half of affected patients (Fig. 35-23

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