Causes of varicose veins

Veins exist in all parts of the body. There are two sets of veins in the legs, superficial and deep. The superficial veins connect to the deep veins by small vessels (perforators). The deep veins are not involved in the formation of varicosities. The superficial veins are located just below the skin and may be slightly visible. All leg veins have valves which open and close. The function of all veins is to return the blood back to the lungs. However, occasionally the superficial veins in the leg develop varicosities.

In general, superficial veins in the legs are very thinned walled and have little muscle. They do not have much capacity to tolerate any type of high pressure in them. Varicosities can develop any time when the superficial veins are exposed to high pressures. The high pressures cause distension of the veins and thus the valves can no longer close snugly. This leads to engorgement of the veins with blood and hence to varicosities. If for some reason the small veins connecting the deep and superficial veins are damaged (usually from a blood clot), the superficial veins will then be exposed to slightly high pressures.

Any condition that either damages the valves or the superficial vein and/or causes high pressures will lead to the development of varicose veins.

The most common causes of varicose veins include:

Age: As we age our veins start to weaken and the valves start to wear down. The elasticity of the veins and the thin muscle layer around the vein starts to weaken and the veins can no longer push the blood out. The wear and tear of the veins with age, eventually leads to enlargement of the veins and development of varicose veins.

Trauma: Any trauma to the legs can injure the superficial veins and later on lead to development of varicose veins. Trauma may injure the valves or the veins itself. Most individuals who have had leg trauma usually have life-long swelling of their legs.

Estrogen: The female sex hormone, estrogen, is associated with an increase in the incidence of varicosities. Estrogen is thought to cause thinning of the veins and valves. This leads to collection of blood in the veins. This may be one reason why more women than men have varicose veins.

Obesity. In general, varicose veins are more common in obese individuals. The reason is believed to be due to the excess weight and fluid. The veins do not have a lot of capacity to endure the persistent high pressures and eventually varicosities result.

Pregnancy: Pregnancy is a very high risk for the formation of varicose veins. Women are particularly susceptible to varicose disease because the thin vein walls and valves get distended under the influence of fluid, weight gain and the sex hormones. Over time the sex hormones weaken the vein and soften the valves. Late in pregnancy, the enlarged uterus compresses the veins in the pelvis and exerts a significant pressure on the leg veins. All of this leads to development of varicose veins. Once varicose veins have formed during pregnancy, they never disappear. In fact, women with multiple pregnancies, usually develop the visible "rope like" varicosities along the entire leg.

Genetics: Varicose veins do tend to run in families. If one member of the family is affected, the chances are high that other members of the family may also develop varicose veins.

Idiopathic: Some individuals develop varicose veins despite having no risk factors or in the absence of any elevated venous pressure. This is what is known as "bad luck".

Straining: There are some individuals who have constant high pressure in the lower abdomen. Conditions like chronic constipation and persistent coughing tend to increase the venous pressure in the groin area. This persistently increased abdominal pressure may be responsible for varicose veins. Hemorrhoids (type of varicosity) are a classic example of a disorder which is developed by constant straining.

Standing: Prolonged standing is known to be associated with development of varicose veins. When standing in one position, the leg muscles do not work and the veins are not able to push the blood back to the heart. The prolonged standing leads to increased venous pressure in the legs which slowly weakens the valves; leading to the development of varicose veins.

Blood clot: Anyone who has developed a prior blood clot in the leg veins is more susceptible to development of varicose veins. The blood clots may occur anywhere along the vein and they destroy the valves in the veins. The majority of individuals with a prior blood clot in the legs tend to have persistently enlarged legs with marked varicosities.