Chronic venous insufficiency
Loss of the venous function in the lower leg. May be post-thrombotic, i.e. following a deep venous thrombosis which may destroy valves that maintain the one way flow. Thrombophlebitis may have a similar effect.
The venous return in the legs is mostly carried by deep veins (venae comitantes) with the superficial veins (saphenous venous systems) carrying only a minority of the blood flow. At several levels, typically the posterior calf, popliteal fossa and sapheno-femoral junction, there are perforating veins that allow blood to flow from the superficial to the deep system. Valves with the veins maintain the flow of blood.
As a slight simplification, if a valve fails at one level, there is a higher column of blood and therefore hydrostatic pressure above the next valve down. This next valve may fail and so on, resulting in higher pressures expanding the veins and resulting in varicosities.
If this occurs in the superficial venous system, but the deep veins are competent, then it is possible to surgically remove the varicosities as the majority of the blood is carried by the deep veins.
If it occurs in the deep veins, then venous insufficiency may result. This may manifest as: