Atypical spontaneous aorto-caval fistula: CT appearance

CT findings of a clinically occult abdominal aorto-caval fistula secondary to atherosclerotic abdominal aortic aneurysm are presented. A review of 20 CT's demonstrating nonruptured abdominal aortic aneurysm was conducted. This review, in conjunction with the case presented, suggests that extensive caval effacement, with loss of the aorto-caval fat plane is an uncommon finding, and may indicate the presence of a thrombotically occluded aorto-caval fistula.