Rare Occurrence of Lower Pole Ureteropelvic Junction Obstruction in a 78 year old Female with a Completely Duplicated Collecting System

Duplication of the ureters is the most common congenital anomaly of the upper collecting system and it may be either a partial or a complete duplication (3,4). Based on autopsy results, partial duplication is thought to occur in approximately 1 in 150 cases and complete duplication in 1 in 500 cases. Clinically however, completely duplicated systems appear to be more common, likely due to the fact that a complete duplication is more likely to produce symptoms than a partial duplication (4). During organogenesis, the ureter forms as a bud from the mesonephric duct. A normal kidney is formed when this ureteric bud invaginates the metanephric blastema. The collecting system is formed through multiple branchings of the ureteric bud after invaginating into the metanephric blastema. Partial duplication results when the single ureteric bud branches before it connects to the metanephric blastema. This results in a bifurcation of the ureter which may occur at any level from the bladder wall to the renal pelvis. Complete duplication of the ureter occurs when two separate buds originate from the mesonephric duct. These buds then invaginate the metanephric blastema separately and consequently form two separate upper and lower collecting systems (4).

As the mesonpehric duct migrates caudally during embryonic life, the ureter from the lower moiety attaches to the bladder close to the normal location. The ureter from the upper moiety however remains attached to the mesonephric duct longer during its caudal migration and attaches ectopically into the bladder, more inferiorly and medially (4). As described in the Weigert-Meyer rule, with complete ureteral duplication, the ureter draining the upper pole passes through the bladder wall to insert inferior and medial to the normally placed ureter that drains the lower pole. The upper pole ureter often ends as an ectopic ureterocele that is obstructed because of its ectopic insertion. The lower pole ureter inserts in or near the normal location in the bladder trigone and is subject to vesicoureteral reflux because of distortion of its passage through the bladder wall by the ectopic ureterocele. A majority of complete and incomplete duplicated collecting systems function normally, and as a result, are discovered as incidental findings on imaging studies (1,4).

In the pediatric population, UPJ obstruction is the most common cause of upper urinary tract dilation. There is a 2:1 male predominance, and the left kidney is affected two times more than the right (5). Although UPJ obstruction is seen less commonly in adults than in neonates, it is not a rarity in adults. A UPJ obstruction is a functional or anatomic obstruction to urine flow from the renal pelvis to the proximal ureter resulting in symptoms or renal damage (6). Etiologies of UPJ obstruction in adults range from obstructive stones, acquired stenotic lesions (from upper tract infections, trauma or ischemia), extrinsic compression (from retroperitoneal fibrosis, or crossing vessels), or congenital anomalies (5). Congenital UPJ obstructions are most often the result of an aperistaltic segment of the ureter due to an anomalous arrangement of smooth muscle cells within the upper ureteral wall (5,6). Congenital UPJ obstruction can present clinically at any age time from the intrauterine period to old age, as it did in our patient.

Although UPJ obstruction and duplicated collecting systems are common abnormalities, they rarely occur in combination (7, 8, 9, and 10). Ho et. al described seven cases of UPJ obstruction in patients with duplicated collecting systems. All cases described were in the pediatric population, with ages ranging from 3 weeks to 14 years. Three of the seven cases involved obstruction of the upper moiety (8). Ulchaker et. Al. describe four cases of UPJ obstruction occurring in duplicated collecting systems. In his case series, the age range was from 5 months to 10 months and all of the obstructions were seen in the lower pole moieties (10).

The detection of UPJ obstruction in a duplicated collecting system in an adult patient has not been described. In this case report, we describe the rare occurrence of UPJ obstruction in the lower pole moiety in a 78 year old woman with a duplicated collecting system.