We describe an unusual case of xanthogranulomatous pyelonephritis (XGPN) in a 73-year-old woman diagnosed after a blunt abdominal trauma. This case is unique because of the atypical presentation, with absence of symptoms, normal laboratory exams, and unusual computed tomography and magnetic resonance imaging findings. The patient underwent radical nephrectomy because a renal cystic tumor was suspected. Only the histopathological findings suggested the final diagnosis of XGPN.