Chronic expanding hematoma in the retroperitoneal space: a case report.

A case of retroperitoneal chronic expanding hematoma complicated with hydronephrosis, which was difficult to diagnose preoperatively, is reported. The patient was a 70-year-old man. An 18 cm mass was detected in the right retroperitoneal space on abdominal CT screening. There were small calcifications in the periphery of the mass that were strongly enhanced in the delayed phase of dynamic CT. The mass involved the right ureter and iliopsoas muscle, resulting in severe hydronephrosis. The histological diagnosis was chronic expanding hematoma.