Zinner Syndrome: A Narrative Review of Imaging Findings with an Illustrative Case Report.

Zinner syndrome is a rare congenital anomaly of the male genitourinary tract, characterized by the triad of unilateral renal agenesis, ipsilateral seminal vesicle cyst, and ejaculatory duct obstruction. Owing to its low prevalence and nonspecific clinical presentation, diagnosis is often delayed or incidental, with imaging playing a central role in detection and characterization. This study presents a narrative review with an illustrative case report, aiming to summarize the imaging features of Zinner syndrome, outline the main radiologic differential diagnoses of seminal vesicle cysts, and highlight common diagnostic pitfalls, with emphasis on cross-sectional imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI). The narrative review of the literature highlights that CT and MRI are essential for accurate anatomical localization, characterization of cystic content, and identification of associated genitourinary anomalies. MRI, in particular, provides superior soft-tissue contrast and is considered the reference modality for diagnosis and differential evaluation of male pelvic cystic lesions. Key differential diagnoses include Müllerian duct cysts, prostatic utricle cysts, and ejaculatory duct cysts. As an illustrative example, we report the case of a young adult male presenting with pelvic discomfort, infertility, and mild lower urinary tract symptoms. Imaging findings, including ultrasound and cross-sectional studies, demonstrated a seminal vesicle cyst associated with ipsilateral renal agenesis, consistent with Zinner syndrome. Zinner syndrome should be considered in the evaluation of male pelvic cystic lesions, particularly in the presence of unilateral renal agenesis. Awareness of its characteristic imaging features is essential for accurate diagnosis and appropriate management, with MRI playing a pivotal role in confirming the diagnosis and distinguishing it from other pelvic cystic entities.