Bear Paw Sign: Xanthogranulomatous Pyelonephritis.

Xanthogranulomatous pyelonephritis is a rare form of chronic pyelonephritis in which the involved areas of the kidneys are destroyed and replaced by foam cells. It usually occurs in immunocompromised middle-aged females with ureteral obstruction or chronic urinary tract infection induced by the formation of renal stones. We herein report the case of a 44-year-old woman, with a history of left kidney staghorn calculi and recurrent urinary tract infections. Abdominal computed tomography showed the 'bear paw' sign, typical appearance of XGP and patient underwent a nephrectomy with uneventful post-operative course.