Venous insufficiency is the inability or difficulty of the leg veins to return blood back to the heart. As the blood pools in the leg it leads to heaviness and swelling at the end of the day and over time it may gradually progress to spider veins, varicose veins and even skin discoloration and ulcers at advanced stages.
Varicose veins are enlarged veins that are visible through the skin and may appear as blue or purple twisted, knot-like cords on the leg.
Spider veins, a milder type of varicose veins, are smaller than varicose veins and often look like a sunburst or "spider web." They are red or blue in color and are commonly found on the legs, just under the surface of the skin.
Vein Anatomy and Venous Insufficiency:
Veins should not be confused with arteries. The arterial system directs blood flow (rich in oxygen) from the heart to the body while the venous system returns blood (poor in oxygen as it has been consumed) back to the heart. Have you noticed that medical illustrations indicate the blood vessels red and/or blue? The red blood vessels represent the arteries, the blue ones represent the veins. This simulates reality as indeed high oxygen levels in the arterial blood give it a bright red color, while low oxygen levels in the venous blood make it look dark blue.
Our legs have two distinct systems of veins: superficial and deep. The superficial system is made up of veins that are close to the skin, the major ones known as "great saphenous vein" (inner side of the thigh and lower leg) and "small saphenous vein" (back side of the calf). The deep system is comprised of larger veins deep within the muscles of the leg. The two systems are connected by small communicating (perforator) veins. All veins eventually merge to form the big central veins in the abdomen and chest. Venous return to the heart occurs predominately through the deep veins and this is of particular importance as when the superficial veins are diseased (e.g. varicose veins) they can be removed without disturbing the venous circulation since it is then deviated through the deep veins.
A major difference of the veins compared to the arteries is that veins have one-way valves. Arteries do not need valves as the blood flow is maintained by the pressure generated by the heart pumping. Blood pressure in the veins is lower than that of the arteries and valves facilitate blood flow (e.g. maintaining flow "upwards" against the gravity). When the leg muscles contract they squeeze the deep veins and the valves open. When the leg muscles relax the valves close preventing blood from flowing backward. When the one-way valves become weakened or damaged, blood flows backward and pools in the veins, stretching them as a result of increased pressure. This stretching of the veins weakens further the walls of the veins and damages even more the valves. This is called venous insufficiency. Spider veins or thick varicose veins may subsequently result.