Bilateral subcapsular and perinephric hemorrhage as the initial presentation of polyarteritis nodosa.

Polyarteritis nodosa is a systemic vasculitis of medium and small-sized arteries associated with aneurysm formation. Aneurysms may be complicated by thrombosis, rupture and hemorrhage. Kidney involvement in polyarteritis nodosa can rarely be complicated by Wunderlich syndrome which is characterized by acute onset of spontaneous, nontraumatic subcapsular and perirenal hematomas. A 22-year-old woman with mental retardation due to childhood cytomegalovirus infection presented with flank pain, weight loss and fever, and was found to have bilateral subcapsular and perinephric hematomas. Spontaneous bilateral renal hemorrhage as the initial manifestation of polyarteritis nodosa is rare, and it can be associated with delays in diagnosis and treatment.