Renal Collecting System Duplication

Renal Collecting System Duplication – Ectopic Insertion

CT – Bilateral dilated distal ureters. The right ureter continues distal to the bladder neck.

MR – Urography demonstrates bilateral renal duplication. Sagittal, axial and coronal images of the pelvis show insertion of the upper pole ureter into the vagina.

Ureteroceles represent a cystic dilatation of the intravesical segment of the ureter. This condition can be congenital or induced by inflammation. A congenital ureterocele is a hyperplastic response to the congenital obstruction of the ureteral meatus and nearly 75% are associated with a duplicated ureter. The size of the ureterocele is variable and can range from as small as one centimeter to as large as the bladder, itself. There are two types of ureteroceles: simple and ectopic. A simple ureterocele arises from a normally-positioned ureteral orifice and an ectopic ureterocele arises from an abnormally-positioned ureteral orifice. Both can be associated with either a single or duplicated collecting system.

Ectopic ureteroceles are located more inferior and medial than simple ureteroceles and are nearly always associated with the superior-pole of the renal collecting system. Ectopic ureterocele is usually unilateral andmore common in females. The typical ultrasonographic appearance is of an ectatic superior-pole collecting system of a duplex kidney that is connected to a tortous, ectatic ureter. At the level of the bladder, this hydroureter terminates in a round, thin-walled, anechoic intravesical cavity located outside the normal location of the ureteral meatus.

Evaluation with a voiding-cystourethrogram is recommended to evaluate for the presence of vesico-ureteral reflux and bladder neck obstruction. If vesicoureteral reflux is present, it typically occurs into the orthotopic (lower pole) ureter in a duplicated collecting system. Conventional or MR urography are often necessary to define the site of ureteral insertion.

Berrocal T, Lopez-Pereira P, Arjonilla A, Guitierrez T. Anomalies of the distal ureter, bladder and urethra in children: Embryologic, radiologic and pathologic features. Radiographics (2002); 22:1139-1164.

Tod Mattis, MD