Venous insufficiency. Leg with discolouration and flaking skin due to chronic venous insufficiency, or inadequate blood flow through the leg veins. This form of peripheral vascular disease can have several causes: the narrowing of the blood vessels (stenosis); the formation of a blood clot in a vein, which is known as deep vein thrombosis, or, if the vein is also inflamed, thrombophlebitis. Lack of blood produces pain and aching after walking, and can lead to leg ulcers or even gangrene. Blood clots are normally treated with anti-inflammatory, anticoagulant and thrombolytic (clot-dissolving) drugs, although surgery may sometimes be necessary.