An unusual presentation of xanthogranulomatous pyelonephritis: psoas abscess with reno-colic fistula.

Xanthogranulomatous pyelonephritis (XGP) is a rare histological subset of pyelonephritis characterized by being a chronic destructive granulomatous inflammation of the renal parenchyma. XGP is classified according to the extent of disease into two entities: within the renal cortex (focal or segmental XGP) or diffuse spread with pelvic communication (diffuse XGP). Although rare, XGP can have fatal complications including perinephric, psoas abscess, nephro-cutaneous fistula and reno-colic fistula. Only few studies have reported XGP complicated with psaos abcess and reno-colic fistula. Our aim is to add to the literature and share our experience with a case of extensive XGP eroding into the psoas muscle and ascending colon leading to severe sepsis that was successfully managed. We report a 56-year-old woman who was found to have XGP complicated by psoas abscess and reno-colic fistula managed by antibiotics, nephrostomy, and subsequent nephrectomy and partial colectomy.