IS Case 112: Incomplete Duplication of the Left Ureter
Imaging Sciences URMC 2008
Publication Date: 2009-05-20
Two fluoroscopic images one with full bladder (Fig.1) and a post-void (Fig. 2) from a voiding cystourethrogram (VCUG) demonstrate severely dilated and tortuous ureters with dilatation of the renal pelvis and severe blunting of the calyces bilaterally. There is a third mildly dilated ureter (arrowheads) which drains the upper pole of the left kidney (arrow) and appears to fuse with the lower segment of the ureter draining the left lower pole.
The most common urinary tract anomaly is duplication of the ureters which occurs in 12-15% of the population. The embryologic evolution of a duplex system is the basis for the Weigert-Meyer rule and accounts for the development of the three most common complications which are vesicoureteral reflux, ectopic ureterocele, and ectopic ureteral insertion. The first ureteral bud to arise from the Wolffian duct is destined to drain the future lower pole of the kidney and the vesicoureteral orifice migrates superolaterally with growth of the urogenital sinus. If the final location is laterally displaced from normal, the intravesical portion that forms the valve mechanism may be short making the lower pole moiety prone to vesicoureteral reflux. The second ureteral bud associated with the upper pole moiety emerges later and the vesicoureteral orifice migrates inferomedially eventually terminating in the bladder or inserting ectopically into derivatives of the Wolffian duct such as the seminal vesicle, vas deferens, ejaculatory duct and prostatic urethra in males or the vagina, urethra, urethrovaginal septum and Gartner ducts in females. The upper pole moiety may also insert into an ectopic ureterocele in which case there is a dilated intravesical segment. As a consequence of ectopic ureteral insertion or an ectopic ureterocele, the upper pole moiety in a completely duplicated system tends to be obstructed. This results in hydronephrosis of the upper pole with mass effect and inferolateral displacement of the lower pole creating the "drooping lily sign" on VCUG or excretory urography.
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