Also known as venous insufficiency, venous disease is usually associated with varicose veins and leg heaviness. In simplest terms, it is a lack of blood flow towards the heart from the legs. There are two main types of vessels in the body; you can think of them as plumbing. Arteries take blood from the heart to different parts of the body and veins take blood back to the heart. Within your veins are important valves that open and close, directing the blood toward your heart. Venous disease occurs when the valves become stretched or flabby, allowing blood to flow down and pool in the legs.