Varicose veins are distended veins, usually in the superficial veins of the thighs and legs. Varicose veins are caused by the valves inside the veins becoming stretched so they no longer close completely. The affected veins then become filled with blood. There are usually no serious medical problems associated with varicose vein.
Constriction, the build-up of plaque, or clots can restrict blood flow in veins or arteries. (From Willis, M.C. Medical Terminology: A Programmed Learning Approach to the Language of Health Care. Baltimore: Lippincott, Williams & Wilkins, 2002.)