Venous insufficiency is a condition in which the flow of blood through the veins is impaired. Venous insufficiency can be caused by a number of disorders of the veins, particularly deep vein thrombosis
(blood clot) or varicose veins
In healthy veins, there is continuous flow of blood from the limbs back toward the heart. There are valves within the veins of the legs that prevent the back flow of blood. Venous insufficiency occurs when forward flow through the veins is obstructed, as in the case of a blood clot, or if there is backward leakage of blood flow through damaged valves. In many cases of venous insufficiency, patients have both obstruction of forward flow and backward leakage of the veins.
The most common causes of venous insufficiency are previous cases of blood clots and varicose veins. In some cases, weakness of the leg muscles that help squeeze blood forward may also contribute to venous insufficiency.