A 36-year-old m an had stage B1 bladder cancer-treated by cystectomy and ureterosigmoidostomy. Postoperatively, a urinary leak was managed successfully by transureteroureterostomy and temporary colostomy. In succeeding years a large calculus developed in the region where the bladder had been and it also involved the sigmoid colon. The huge stone was removed successfully. A nonabsorbable suture was found in the center of the stone. This is a unique complication of ureterosigmoidostomy.