False-positive PSMA uptake from urinary reflux into a seminal vesicle cyst in renal agenesis

Prostate-specific membrane antigen positron emission tomography is increasingly used in the evaluation of suspected prostate cancer, but radiotracer activity may occur in benign or congenital conditions and lead to false-positive interpretation. Although urinary tracer activity is often considered in patients with prior prostate or urinary tract surgery, congenital genitourinary anomalies can produce a similar imaging pitfall in patients without previous surgical intervention. We describe a seventy-three-year-old man with an elevated prostate-specific antigen level, no history of prior prostate or urinary tract surgery, and an indeterminate lesion on prostate magnetic resonance imaging who demonstrated focal tracer activity near the right seminal vesicle on prostate-specific membrane antigen positron emission tomographic imaging. Additional post-void imaging showed radiotracer accumulation within the right seminal vesicle region, and correlation with magnetic resonance imaging suggested reflux of urine into a cystic seminal vesicle remnant containing a small calculus. Further assessment revealed absence of the right kidney, consistent with a congenital renal tract anomaly linking the seminal vesicle abnormality and urinary reflux. Biopsy demonstrated benign prostatic tissue, confirming reflux of urine rather than malignancy as the cause of radiotracer uptake. This case highlights a rare interpretative pitfall in a patient without prior prostate surgery and emphasises that awareness of congenital anomalies involving the seminal vesicles can improve diagnostic confidence and reduce unnecessary biopsy in future cases.