Venous
Incompetence - varicose Veins
One of the most common problems with the veins of the leg is failure of
their valves. This occurs frequently in the superficial venous system
resulting in varicose veins, which affect 10—20 per cent of the adult
population in Westernised countries. In developing countries, where a
primitive way of life is maintained, there is a very low incidence of varicose
veins. The reasons for this difference are unclear but are probably related to
differences in diet. A further major factor is inheritance: women in whom
neither parent has varicose veins have a 10 per cent risk of developing varices,
but when both parents are affected there is an 80 per cent chance. Men are
affected less frequently than women.
The
mechanisms that cause the superficial vein valves to fail have not been fully
established. What appears to happen is that first a small gap appears between
the valve cusps at the commisure (where the valve leaflets join the vein wall).
This gap widens and more reverse flow (venous reflux) is allowed. The valve
cusps degenerate and holes develop in them. Eventually they disappear completely (Fig. 16.7). The vein below the valve
responds by dilating. Varicose veins may eventually reach five times their usual
size if left to develop for long enough.
In
the past it was thought that varicose veins were caused by anatomical
abnormalities in the deep vein valves. It is now clear that this is not true.
Varicose veins often develop in the calf when the veins above are normal. This
seems to be a process where congenital and environmental factors accumulate to
cause valve failure.
Varicose
veins are thought to develop more often in people who stand during their work.
People who sit or walk are at less risk of developing varices. They often
develop during pregnancy under the influence of oestrogen and progesterone which
cause the smooth muscle in the vein wall to relax.
Clinical
features
Varicose veins are very common; they may either give no symptoms or
cause aching and discomfort in the legs. Varices are recognised as tortuous
dilated veins in the leg, but physiologically speaking a varicose vein is
one which permits reverse flow through its faulty valves. Varices of the
major tributaries of the saphenous veins or the saphenous veins themselves are
large (5—15 mm diameter) and usually start in the calf (Fig.
16.8).
Later varices of the long saphenous system may also appear in the thigh.
Patients may develop much smaller varices. These range from 0.5-mm diameter
vessels in the skin, which are commonly referred to as thread veins or
dermal flares, and are usually purple or red in colour. Slightly larger veins
(1—3 mm diameter) lying immediately beneath the skin may also present as small
varicosities. These are usually referred to as reticular varices. The
association of thread veins and reticular varices is frequently seen, and these
probably reflect a type of varicose veins which is confined to the smallest size
of vein. These tiny veins are associated with superficial venous incompetence in
about 30 per cent of
Occasionally complications of varicose veins may develop. These include thrombosis,
which is referred to as superficial thrombophlebitis. Usually this remains
in the superficial veins and may cause considerable discomfort. Sometimes