Abnormal Valves

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Venous insufficiency can occur because of  a problem with the veins themselves or a weakness of the pumping mechanism of the calf. The two are usually associated. This leads to reflux of the column of blood through the leaky valve. Turbulent flow often occurs as a result and over time this can lead onto to strain on the vein wall. This then produces stretching and weakness at various points along the vein ultimately resulting in the familiar wiggly vessels called varicose veins. The dilatation of the vein makes the valve leakage worse and so on. The main causes can be summarised as follows:

  • Congenital abnormalities of the veins.
  • Post-thrombotic damage to the valves of the deep system.
  • Superficial venous incompetence.

Congenital anomalies are not that common but deep vein thrombosis and superficial vein failure leading to varicose veins are. Thrombosis can occur in a variety of situations but generally any cause of stagnation in the veins can lead to clots forming in the veins. An extreme example is shown in the picture.

(Click thumbnail to see larger picture)

This sets up an inflammation of the lining of the vein and the valves get destroyed in the process. Although clot busting factors in the blood can open the vein up again, the valves are not replaced. This leads to uncontrolled reflux which means that the muscles of the legs have to work harder to to pump the same amount of blood as before. A young fit person may be able to compensate but eventually the calf pump becomes overwhelmed leading to swelling of the limb, varicose veins, dermatitis and in severe cases, ulceration. The following factors place people at most risk of developing a deep vein thrombosis:


  • A major operation or illness.
  • Cancer.
  • Pregnancy or recent childbirth
  • Major accidents.
  • Prolonged immobility.
  • Any factor leading to prolonged compression of a major vein.
  • Blood abnormalities
  • Metabolic causes (dehydration, high lipids and cholesterol, heart failure)
  • Some drugs (i.e. the contraceptive pill