Vein valves and the direction of blood flow can be seen on ultrasound. Ultrasound is an important tool in the diagnosis of venous reflux disease.

 

In the circulatory system, the veins carry de-oxygenated blood back to the heart. The leg veins carry blood toward the heart, against gravity. Therefore, the leg veins have one-way valves the prevent back flow of blood. When the valves do not function properly, they allow blood to flow backward, causing pooling of blood. This  is referred to as venous reflux or venous insufficiency. Eventually, the backflow of the blood will cause varicose veins to develop and symptoms related to the increased pressure in the leg veins such as leg heaviness, aching, swelling, restless legs, night cramps, throbbing and pain.

The vein valve no longer works properly, blood back flows across the valves. This image shows reflux in the great saphenous vein.

 

vein valve in the great saphenous vein in the thigh.