Your legs are made up of a network of veins. A healthy vein contains valves that open and close to assist the return of blood to the heart. Varicose veins are caused by damaged or diseased valves, which result in backward flow of blood in your legs, a condition known as superficial venous reflux. This can cause blood to pool in your legs and lead to symptoms such as pain, swelling and varicose veins.
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