Early enhancement of the inferior vena cava on helical CT

Arteriovenous fistulas (AVFs) are abnormal communications between the arterial and the venous systems. We describe two cases in which an aortocaval fistula (ACF) and a deep femoral AVF were diagnosed on dynamic computer tomography (CT) by early transient enhancement of the inferior vena cava (IVC). Awareness of the specific CT features found in central and peripheral AVFs and the effects on the arterial and venous systems may enable the radiologist to make the diagnosis.