We report two cases in which the renal stone originated from a foreign body which was used to treat a urinary tract fistula by a gynecologist. The first patient developed a vesicovaginal fistula following an emergency Caesarean operation. At the time of correcting surgery, a 5 Fr ureteral catheter was used as a splint catheter elsewhere, 108 mm of which somehow migrated up to the renal pelvis and a stone was formed 4.5 years later. The second patient underwent a radical hysterectomy for uterine cervical cancer. Postoperatively, a ureterovaginal fistula developed, for which a double-J ureteral catheter was indwelt. When she visited our clinic 6 months later, we found the double-J catheter and renal stone in her left renal pelvis. In both cases the catheters and renal stones were successfully removed by means of the percutaneous nephrolithotomy (PNL).