Duplex ultrasound scanning is now the gold standard and first diagnostic test for assessing the lower limbs in patients with suspected varicose veins, CVI or DVT. Duplex ultrasound scanning is a noninvasive, safe, reliable, and cost-effective test that can assess for venous obstructions, turbulence, and the direction of the flow of venous blood.
It is important to evaluate the deep venous system for any obstructions, especially for those patients who have a history of DVTs, because an obstruction in the deep veins would affect any treatment of superficial varicose veins and would adversely influence long-term results.
The direction of venous blood flow is also assessed for any reflux. Retrograde, or backwards, flow that lasts for less than 0.5 seconds is normal (ie, no reflux), whereas retrograde flow that lasts for more than 0.5 seconds is considered positive for reflux and would indicate the presence of incompetent valves or veins.