Varicose veins. Coloured angiograms (X-rays) of two views of a leg, showing the presence of varic- ose veins (yellow). Bone is green. These swollen, lengthened and tortuous veins form due to defect- ive valves in the veins of the leg. As blood circulates around the legs, valves prevent it from sinking to the feet under gravity. If the valves stop working, blood pools downwards causing varic- ose veins. Treatment includes elastic support, stripping (avulsion) or sclerotherapy, where blood is re-routed by blocking the vein with an irritant injection. The angiograms were produced by inject- ing a radio-opaque dye into the blood system.