A varicose vein is a peripheral vein that is dilated (abnormally expanded), tortuous (twisted), and thick-walled. Varicose veins are often found in the lower extremities. Both increased venous pressure, as from heart failure or vena cava compression due to pregnancy, resulting in the incompetence of the valves of the veins, as well as weakened vessel wall of the veins may be contributory to the formation of varicose veins.