[Non-traumatic retroperitoneal hemorrhage from renal adenoma].

A 37-year-old woman presented to our hospital with the chief complaints of stroke and sudden onset of pain in the left flank. An abdominal ultrasonogram showed a solid tumor and abdominal CT revealed a tumor 3 cm in diameter and a capsule with a heterogeneous interior at the left lower pole of the kidney. This tumor was accompanied by retroperitoneal hemorrhage. Selective left angiogram showed an avascular tumor with an artery entering the region surrounding the tumor itself. Based on the above mentioned findings, rupture of a renal angiomyolipoma was suspected. However, renal cancer could not be ruled out. Surgery was performed. At operation, a frozen section showed no malignancy, and partial nephrectomy was performed. The tumor measured 3.0 x 3.5 x 3.5 cm, and had a capsule that was 3 mm thick; its interior was filled with brown necrotic tissue mixed with red-brown coagulated blood. The histological diagnosis was a tubulo-papillary renal adenoma, but since the inside of the tumor had undergone extensive necrosis a well-differentiated adenocarcinoma could not be excluded. A renal adenoma manifesting clinical symptoms is rare, and this case of pain caused by retroperitoneal hemorrhage is the first to be reported in Japan. It is difficult to diagnose renal adenoma by preoperative imaging and intraoperative frozen section examination. Diagnosis is considered to be difficult in some cases even when examining permanent specimens. Therefore, the type of surgery used in affected patients should also be investigated in the future.