We report on 8 patients who presented with acute abdominal pain, palpable mass and a rapid decrease in hemoglobin. Intravenous pyelogram, ultrasound and computed tomography had been performed but the underlying cause of the perirenal hematoma couldn't be detected. Surgical exploration was decided and 6 total and 2 partial nephrectomies were performed. The pathological report revealed 4 adenocarcinomas and 4 angiomyolipomas. The possibility of spontaneous rupture of the kidney in the evaluation of cases of acute abdomen is particularly stressed.