Crossed renal ectopia is a rare congenital malformation. We report a case in a 77-year-old man presenting with a left lower abdominal mass. Abdominal computed tomography showed a vascular lesion that developed in a right-to-left crossed-fused renal ectopia. The patient was treated with radical heminephrectomy. Appropriate preoperative imaging and surgical technique for the isthmusectomy are highlighted.