A 30-year-old male patient with no past medical or surgical history presented with non-specific left groin pain. He had an abdominal ultrasound (not available) that showed a single right kidney and left-sided pelvic cystic mass with turbid content. CT was requested.

CT shows left renal agenesis and seminal vesicle cyst but may be insufficient to confirm the diagnosis, for which MRI was recommended.

A pelvic MRI was performed to accurately identify the origin of the cystic mass. MRI is confirmatory and makes the definitive diagnosis of a seminal vesicle cyst, which appears in both T1WI and T2WI as a hyperintense structure (due to hemorrhage and a high proteinaceous concentration in the seminal fluid). 

The patient in our case complained of nonspecific symptoms - the most common presentation. Patients with Zinner syndrome show a triad comprising unilateral renal agenesis, ipsilateral seminal vesicle cyst, and ejaculatory duct obstruction

A differential diagnosis such as prostatic utricle cysts or acquired seminal vesical cysts could be ruled out based on imaging findings and patient history. 

 Characteristic radiological appearance of Zinner syndrome is sufficient for the radiologist to arrive at an accurate diagnosis.