Zinner Syndrome: A Case Report.

Zinner syndrome is an uncommon congenital disorder of the male genitourinary tract that arises from maldevelopment of the distal mesonephric (Wolffian) duct. On the affected side, it combines a seminal vesicle cyst, ejaculatory duct obstruction, and renal agenesis. Because it is frequently asymptomatic, it is often discovered incidentally on cross-sectional imaging. We report the case of a 40-year-old man under oncologic surveillance for treated colonic adenocarcinoma in whom follow-up computed tomography (CT) incidentally revealed a retrovesical cystic lesion of the left seminal vesicle associated with ipsilateral renal agenesis and ectopic insertion of the left ureter into the cyst - a constellation diagnostic of Zinner syndrome. Although magnetic resonance imaging (MRI) remains the reference standard for characterizing seminal vesicle anomalies, CT was sufficient for a confident diagnosis in this characteristic case. The absence of a directly visualized dilated ejaculatory duct did not preclude the diagnosis, as this feature is inconsistently demonstrated on CT and is usually inferred from the associated mesonephric duct anomalies. The syndrome should therefore be suspected in any man in whom a retrovesical cyst coexists with the absence of the ipsilateral kidney, and CT may confirm the diagnosis in characteristic cases even when MRI is unavailable.