Chronic venous insufficiency is caused by obstruction to venous outflow and/or venous valvular incompetence. Either of these conditions generate elevated venous pressure - particularly in the lower extremity - the consequence of which ranges from the inconvenience of minor varicosities to lifestyle changing venous ulceration. This presentation describes how duplex ultrasound imaging is used to detect obstruction to outflow and to assess the duration of venous reflux in the lower extremity.

An essential component of the study is to verify patency of the deep and the superficial veins. With the patient reclining, vein compressibility is evaluated in the common femoral (CFV), femoral, popliteal and great saphenous (GSV) veins, recording Doppler signals from each vessel. Venous reflux is assessed with the patient standing, weight supported upon the contralateral leg with the examined leg relaxed. A cuff (17-19cm width) is wrapped around the calf (when assessing the popliteal) or the thigh (CFV and GSV). The transducer is positioned to show the examined vein longitudinally, with the gate opened to encompass all of the lumen.The cuff is inflated rapidly to 80mmHg, with deflation following when the Doppler signals have stabilized. Upon deflation, the flow reversal should be <1s at the CFV and <0.5s at the GSV and popliteal. Durations longer than these suggest venous reflux.

Perforator veins are located at the union between the superficial and deep system, where the vein crosses the deep fascia. The deep fascia is seen as a continuous white line, almost horizontal, usually at a depth 1-2cm below the skin surface. The transducer is moved vertically down the leg, looking for a break in the fascia, where there is a vein above and below. The Doppler gate is positioned within the perforator and the limb squeezed either above or below the transducer. The signal should be from superficial to deep, with any flow reversal <0.35s. Perforator diameter can be measured across the break in the fascia.