Contrast-enhanced and color Doppler ultrasound studies. Two-dimensional ultrasound images were obtained at the level of 3-5 cm below the popliteal fossa (PF). The color Doppler studies demonstrated no abnormal vasculature in the same location on the unaffected leg (A), but multiple tortuous vessel structures with pulsatile flow compatible with venous malformation fed by arteriovenous shunts (B). Pulse Doppler studies identified three specific foci of arteriovenous shunts characterized by low-resistance flow, composed of a normal venous waveform with superimposed arterial pulsatile flow (C). The same studies in the unaffected leg demonstrated a normal arterial wave form (D).