Xanthogranulomatous pyelonephritis with a renocolic fistula caused by a parapelvic cyst.

Fistula formation between the upper urinary tract and bowel is an uncommon complication in urogenital diseases. We present a rare case of focal xanthogranulomatous pyelonephritis with a renocolic fistula. This is the first case where a parapelvic cyst obstructs the caliceal outflow and leads to the formation of a renocolic fistula in renal inflammatory disease. It is difficult to make a preoperative diagnosis of focal xanthogranulomatous pyelonephritis with widespread involvement that is caused by non-calculous urinary tract obstruction.