What imaging sign on duplex suggests an arteriovenous fistula after catheterization?

• A. Simultaneous high-velocity arterial and venous flow with early venous pooling and arterialized venous waveforms
• B. Absence of flow in the artery
• C. Only venous flow detected
• D. Normal arterial flow with no venous involvement

Answer: (A)

An arteriovenous fistula after catheterization creates a direct connection allowing arterial blood to shunt into the vein. On duplex ultrasound, the hallmark is simultaneous high-velocity flow in the feeding artery and the draining vein, with the vein showing arterialized, pulsatile waveforms and early venous filling due to the rapid arterial blood entering the venous system. Color Doppler may reveal a jet of flow from artery into vein. This combination—arterialized venous flow plus concurrent arterial flow—best indicates an AV fistula. Patterns lacking this, such as only venous flow, absent arterial flow, or normal arterial flow with no venous involvement, do not reflect a fistula.