A case with fistula formation between a perinephric retroperitoneal abscess, a ureter and a descending colon: Successful outcome after conservative management.

A 72-year-old man diagnosed with hydronephrosis and perinephric abscess because of an impacted urinary stone in the left uretero-pelvic junction was admitted to hospital with high-grade fever. The insertion of a percutaneous drain improved his general condition. Then, imaging from the percutaneous drainage tube revealed a fistula formation between the cavity of the perinephric retroperitoneal abscess, the descending colon, and the left renal pelvis. The patient received conservative management, including insertion of a percutaneous drain, discontinuation of oral intake and antimicrobial chemotherapy. Three days after the percutaneous drainage and discontinuation of oral intake, imaging revealed no apparent fistula. Fistula formation between a perinephric abscess and the descending colon is very rare; this is the first case of a long-term favourable outcome by conservative management.