Spontaneous perinephric hemorrhage: imaging and management. We report on 10 patients with spontaneous perinephric hemorrhage associated with underlying disease, including renal cell carcinoma (5), angiomyolipoma (2), malignant melanoma (1), periarteritis nodosa (1) and severe portal hypertension (1). The etiology could not be identified with computerized tomography (CT) in 5 cases (50%), including 2 renal cell carcinomas, 1 angiomyolipoma, 1 periarteritis nodosa and 1 portal hypertension. Arteriography demonstrated underlying lesions in 4 of these 5 cases (80%) including the case of vasculitis. CT combined with magnetic resonance imaging is accurate for the diagnosis of spontaneous perinephric hemorrhage but the underlying pathological condition is often undetectable in the acute phase due to the perinephric blood. CT should be the first study performed if this diagnosis is suspected. Arteriography is recommended if a renal mass is not detected. If a mass is not identified with these 2 imaging studies and the patient is clinically stable, followup thin slice CT should be performed. 