The veins in the leg carry low-oxygen blood laden with wastes and carbon dioxide back to the heart just as do other veins in the body. However, the leg veins are a bit different in structure from veins elsewhere in the body. This is due to the fact that the blood has to return back to the heart against the force of gravity and has a long distance to travel – from feet to the heart. Special valves in the veins of the leg ensure that blood is gradually pushed up bit by bit towards the trunk of the body. Muscles in the feet and legs act as a pump which gradually push up the blood with every step and movement of the leg. The valves ensures that the blood does not flow backwards to the feet in the time in between each leg movement. Sometimes these valves become dysfunctional and the circulation in the legs becomes sluggish. One of these problems with poor blood flow in the lower limb is varicose veins which appears as unsightly bulging veins in the legs.
What are varicose veins?
Varicose veins in the leg are abnormal enlargement of the leg veins that lie superficially. It is a visible bulging of the veins but indicates a more complex problem known as venous insufficiency of the legs. This means that the blood is not able to maintain a unidirectional (one-way) flow in the vein from the legs to the heart. The sluggish circulation allows blood to pool in the legs thereby causing congestion and a host of other complications associated with impeded venous return. Varicose veins is more common in women and after the age of 60 years but appears to have its roots in early adulthood, and sometimes even childhood, with the condition worsening over decades. Varicose veins is a bulging of the superficial veins in the leg but also increases the risk of another related condition known as deep vein thrombosis (DVT) which involves the deep veins of the leg that are not visible on the surface.
Reasons for varicose veins
It is important to understand the structure and function of the veins when looking at the reasons behind varicose veins. Blood vessels in the body provide a conduit for the flow of blood. In terms of the blood vessels in the lower limbs, arteries carry high pressure oxygen-rich blood from the heart to the leg while veins carry low pressure oxygen-deficient blood from the legs back to the heart. The veins therefore have thinner and less elastic walls than the arteries. Should the pressure in the veins rise for any reason over a prolonged period of time, the vein can become dilated and tortuous.
The veins in the legs have specialized valves that allow blood to flow through it in one direction. However, if the blood flows in the opposite direction, these flap-like valves shut tightly. This is helpful for returning blood flow from the legs back to the trunk against the action of gravity. As blood passes a short distance up the vein, it is held within that segment of the vein and the valves prevent it from draining all the way back down to the feet. Gradually over time this blood can rise higher until it drains into other veins with a more consistent blood flow.
Enlarged leg veins
Varicose veins can occur anywhere in the body although the leg is the most common site. It is essentially a visible defect evident as bulging veins. The varicosities appear in the superficial veins of the legs lying a just short distance under the skin. Normally the blood from the superficial legs veins drain into the deep veins and then travel up the rest of the leg. These deep veins are able to withstand high pressure and therefore do not become dilated.
Once the superficial veins become dilated the flaps of the valves cannot close shut tightly enough. Blood can therefore flow backwards. Even the failure of one valve can have a cyclic effect and lead to failure of other valves. The backward flow of blood increases the pressure in each segment thereby dilating the walls of the leg veins that were not affected. This oxygen-deficient blood accumulates in the leg veins and leads to a host of problems as circulation is affected to the leg. Reduced oxygen supply can lead to leg pain, cramping, discoloration of the skin and skin ulcers.
Causes of varicose veins
Although the mechanism that accounts for varicose veins in known, the exact cause is not always understood. Certain factors that increase the pressure within the superficial leg veins or weakness in the wall of these veins will most likely lead to varicose veins. However, not every person with these risk factors will definitely develop varicose veins.
Loss of supporting tissue with age occurs throughout the body. This also occurs in the wall of the veins. The veins dilate and the valves are compromised.
Pregnancy is one of the more common causes of varicose veins. Several of the numerous changes that occur in the body due to pregnancy contribute to the development of varicose veins.
- Blood volume increases with pregnancy.
- Hormonal changes causes softening of the vein walls and valves.
- The growing uterus presses against the large veins carrying blood from the lower limbs thereby increasing the pressure within it.
Standing for long periods of time can increase the risk of developing varicose veins. The rise in pressure within the veins when standing causes it to dilate over time. Women are especially prone since the hormonal fluctuations with the menstrual cycle makes the vein wall soften and distensible similar to the changes pregnancy.
Hereditary factors also appear to play a role in the development of varicose veins. This is more significant for females born to parents with similar problems or among twins.
Signs and symptoms
The main symptoms of varicose veins include :
- Visible and enlarged veins in the leg that are bulging and twisted. These veins may initially appear green in color but eventually takes on a purple blue hue.
- Aching of the area around the veins although it is not painful or tender to touch. However, there may be no aching in some cases.
- Heaviness or tiredness of the legs.
Other signs and symptoms are seen with venous insufficiency of the legs irrespective of the cause or presence of varicose veins.
- Skin discoloration usually varying from a purple-blue to brown-black color.
- Itchy legs particularly the lower legs and around the varicose veins.
- Burning or throbbing pain in the legs that worsens with standing or sitting for long periods.
- Ulcers on the legs (venous ulcers or stasis ulcers) which more mainly occur around the ankles.
Dangers of varicose veins
If left untreated, varicose veins may lead to certain complications as discussed under the features of venous insufficiency of the legs. The main complications that are of concern includes :
- Venous ulcers which are open sores that form on the leg as a result of reduced blood flow and decreased host defenses. The ulcers may become infected and contribute to the development of conditions such as cellulitis.
- Phlebitis which is inflammation of the veins that typically arises with injury to the leg although it may occur spontaneously in varicose veins. This condition is rarely serious but can further compromise the veins in the long term.
- Deep vein thrombosis (DVT) where blood clots form in the deep veins of the leg. These veins can dislodge and travel through the bloodstream where it eventually block an artery to the lung (pulmonary embolism) which can be fatal.
In this regard, varicose veins can lead to significant discomfort and even disability depending on any underlying problems and the severity. Some of these complications can be very dangerous and even life-threatening.
Article reviewed by Dr. Greg. Last updated on January 25, 2012