Ureteral duplication is not an uncommon anomaly of the urinary tract and there have a been few cases reported of ureteral stones in completely duplicated systems. However, a stone located in an ectopic ureter inserting into the prostatic urethra is very rare.

A case of 39-year-old male who had calculus in duplication ureter with ectopic orifice. He presented with left flank colic pain. A stone in the left lower third ureter was detected by non-contrast CT. No stone was found under endoscopic vision and retrograde pyelography showed the calculus not within the course of observed ureter. However, colic pain persisted after surgery. Intravenous pyelography was arranged for ruling out duplication of ureter. The image confirmed the stone in duplication ureter which has an ectopic ureter orifice inserted below bladder neck.

Second-time ureteroscopy revealed the ectopic orifice in prostatic urethral near the verumontanum by detecting active flow of urine with contrast agent. Ureteroscope was able to pass into the ectopic ureter without difficulty and the stone was successfully managed with laser lithotripsy.

Duplicated systems can be hard to appreciate on non-contrast CT although it has become the gold standard in diagnosis of renal calculus. This case report highlights the importance of contrast image study and skill for searching the ectopic ureter inserting to the prostatic urethra.