A breakdown in the valves of the veins in combination with a chronic dilatation of these vessels results in varicose veins. These appear twisted and swollen under the skin, most commonly in the legs. Contributing factors include heredity, obesity, prolonged standing, and pregnancy, which increases pressure in the pelvic veins. This condition can impede blood flow and lead to edema, thrombosis, hemorrhage, or ulceration. Treatment includes the wearing of elastic stockings and, in some cases, surgical removal of the varicosities, after which collateral circulation is established. A varicose vein in the rectum or anal canal is referred to as a hemorrhoid.

Phlebitis is any inflammation of the veins and may be caused by infection, injury, poor circulation, or damage to valves in the veins. Such inflammation typically initiates formation of a blood clot, resulting in throm-bophlebitis. Any veins are subject to thrombophlebitis, but the more serious condition involves the deep veins as opposed to the superficial veins, in the condition termed deep vein thrombosis (DVT). The most common sites for DVT are the deep veins of the legs, causing serious reduction in venous drainage from these areas.

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