Villous adenoma of the ureter with manifestation of mucus hydroureteronephrosis.

Ureteral tumor is prone to result in lumen obstruction. Villous adenoma is most frequently found in the colon and rectum, seldom in the urinary tract and even more rarely in the ureter or pelvis. Herein, we present a case of bilateral renal stones of more than 10 years' duration with the chief complaint of right flank pain. Obstruction of the right upper ureter with hydroureteronephrosis was observed on sonography, computed tomography and retrograde pyelography. Ureteroscopy revealed papillary tumor obstructing the upper third of the ureter and inducing hydroureteronephrosis with abundant mucoid content. The ureteral tumor proved to be villous adenoma by pathologic examination. It should be noted that ureteral villous adenoma may be related to previous enteric-type metaplastic mucosa or ureteritis glandularis, demonstrates profuse production of mucus, and may eventually undergo malignant transformation.