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Family Doctor Books
Preview of Understanding Varicose Veins

All about varicose veins

Arteries, capillaries and veins

Before talking about varicose veins, it is very important to understand the difference between arteries and veins, and to know something about the normal veins of the legs.
Arteries, capillaries and veins are the tubes that carry blood around the body: they can all be called ‘blood vessels’.

The arteries

As the heart pumps, it sends blood around the body through the arteries. The arteries branch into smaller and smaller vessels, until the blood flows into capillaries. The walls of capillaries are only one cell thick, so that oxygen, glucose and other substances can pass through them to nourish the tissues. The waste materials of metabolism, such as carbon dioxide and lactic acid, filter in the opposite direction into the capillaries. A network of capillaries runs close to the cells in every part of the body, delivering nutrients and taking away waste products in the bloodstream.

The veins

Capillaries join to form slightly larger vessels (venules, or tiny veins) and these in turn join up to form veins. As more tributaries join each main vein, so it gets wider, and eventually blood returns to the heart through the two largest veins – the superior vena cava from the upper part of the body, and the inferior vena cava carrying blood from the legs, pelvis and abdomen. Small veins, joining a larger one, are called tributaries (rather than branches) because blood is flowing up them into the larger vein – like water in the tributaries of a large river.
The blood flowing through the veins is darker than the blood in arteries, because it has less oxygen in it. In contrast to blood flow in arteries, the flow in veins is slower and is not pulsatile. In the leg veins, activity of the leg muscles is important in helping to pump blood back to the heart. Valves in the veins make the blood flow towards the heart. The valves are particularly important in veins of the legs, because blood could otherwise flow the wrong way (downwards) when we are standing up.
 
A network of capillaries runs close to the cells in every part of the body. The capillaries have very thin walls which allows nutrients to pass through into the tissues and waste products to filter back into the capillaries.

Diseases of arteries and veins

The common diseases affecting arteries and veins are quite different. ‘Atherosclerosis’ narrows and blocks arteries, causing heart attacks, strokes and gangrene, but it does not cause problems in the veins. Varicose veins have nothing to do with heart attacks, strokes or amputation of the leg. ‘Thrombosis’ means clotting of blood in a blood vessel and can occur in either veins or arteries, but the causes and effects are different. Thrombosis in the deep veins of the legs can be dangerous (see ‘Thrombosis, phlebitis and bleeding’, page 20), but these veins are different from those forming varicose veins.

The deep and superficial veins of the legs

The veins of the legs are divided into two systems – the deep veins (which run deep to the leathery layer of fascia surrounding the muscles) and the superficial veins (which run in the layer of fat just beneath the skin). The superficial veins are the ones that you can see (for example, on your foot or around the ankle) and they are the ones that can become varicose. It is essential to keep in mind these two different systems – deep and superficial – in order to understand varicose veins and their treatment.

Perforating veins

In a number of places in the leg, the superficial and deep veins are linked by perforating veins (or ‘perforators’). They are called perforators because they perforate the leathery fascial layer surrounding the muscles of the legs. Normally their valves should allow blood to flow only inwards – from the superficial veins to the deep veins. If the valves stop working properly, then blood is pushed out into the superficial veins when the muscles contract: this is one reason for high pressure in the superficial veins, and can be a cause of varicose veins.

Valves in the veins

All the leg veins have delicate valves inside them, which should allow the blood to flow only upwards (towards the heart), or from the superficial veins to the deep ones through the perforating veins. The valves protect against the head of pressure that would otherwise exist in the veins of the legs on standing. If there were no valves, there would be a pressure in the veins at the ankle equivalent to the height of the column of blood all the way up to the heart. It is this head of pressure that causes symptoms and damage when the valves stop working properly, as they often do in varicose veins. A valve occurs every five to ten centimetres in the main superficial veins of the legs.
 
The veins in the leg are divided into two systems – the deep veins and the superficial veins. The two systems are linked periodically by perforating veins. A superficial vein can become varicose because a perforating vein is allowing blood to flow the wrong way (outwards).

The muscle pump

When blood is pumped into the arteries by the heart, it is pushed forwards under high pressure. Only a little of this pressure is left after blood has filtered through the capillaries, to push it through the veins, and the action of the muscles provides a pumping action that helps to push the blood up through the veins. This ‘muscle pump’ is particularly important in the legs, because when we are standing blood has to travel a long way ‘uphill’ to get back to the heart. The deep veins lie within and between the muscles of the calf and thigh. All the muscles are surrounded by a firm leathery layer of ‘fascia’, so as they contract and relax blood is forced up the deep veins. Normally, the valves in the veins make sure that blood flows only upwards in the deep and superficial veins, and inwards through the perforating veins. If the valves stop working, then the muscle pump cannot do its job properly. Damaged valves in the deep veins mean that blood is not pumped upwards, and this can be particularly harmful if the veins at knee level are affected. Failure of valves in the perforating veins allows blood to be pushed out under high pressure into the superficial veins, which can lead to varicose veins.
 
The contraction of muscles compressing veins helps push blood up through the leg veins back to the heart. The valves allow the blood to flow towards the heart only.

Soldiers and the muscle pump

Soldiers give us two good examples about how the muscle pump can be helped to work. Have you noticed how soldiers standing to attention for a long time will sway to and fro just slightly? They have been taught to contract and relax their calf muscles so that blood is pumped up their legs, rather than pooling in the calf veins. Particularly on a hot day, when all the veins are wide and dilated, pooling of blood in the leg veins can occasionally make them faint if they do not do this. The other military lesson about the muscle pump is provided by the puttees that soldiers used to wear, wrapped tightly around their ankles and calves. These formed a firm layer around the whole lower leg (rather like the fascia around the muscles and deep veins) and probably helped the muscle pump to squeeze blood up through the veins during long marches.

Which veins become varicose?

The long saphenous vein (LSV)

This vein and its tributaries are the ones that most often form varicose veins. The long saphenous vein is formed from tributaries in the foot, and is visible in many people when they stand, as the vein just in front of the bone on the inner side of the ankle. It runs up the inner side of the calf and the thigh, and at the groin dives to join the main deep vein (the femoral vein).
 
The long saphenous vein (LSV) and its tributaries most often form varicose veins. The short saphenous vein (SSV) and its tributaries can also become varicose but less often.

The short saphenous vein (SSV)

This is the other main vein under the skin of the leg, the tributaries of which can become varicose, but it is affected much less often than the LSV. The SSV starts just behind the bone on the outer side of the ankle, and runs up the middle of the back of the calf. It usually dives to join the main deep vein just above and behind the knee (the popliteal vein), but this varies and before any operation on the SSV it needs to be checked by a scan.

Perforating veins

In almost any part of the leg, a perforating vein can develop incompetent valves. This allows blood to be pumped outwards under pressure into superficial veins, causing them to become stretched and varicose.

Any vein

Any vein under the skin, in any part of the leg, can become varicose, without valve problems in the LSV, SSV or perforating veins. These varicose veins are usually quite small and cause few symptoms.

Who gets varicose veins?

A lot of studies have been done in different parts of the world, looking for possible causes of varicose veins, but the findings have varied a lot, and it is surprising how few definite answers there are.

Sex

Among the general population in the Western World, about 20 to 30 per cent of women have varicose veins. Most studies have found fewer men with varicose veins (7 to 17 per cent) but, in the recent Edinburgh Vein Study, 40 per cent of the men examined had varicose veins (compared with 32 per cent of the women).

Geography and race

Studies on the incidence of varicose veins have been done in different ways, and have often concentrated on women. Nevertheless, they all seem to show that varicose veins are less common outside the countries of the Western World. For example, prevalences have been found of only two per cent in rural Indian women and about five per cent for women in central and east Africa.

Age

More people develop varicose veins as they get older – at least up to the age of about 60.

Heredity

It is not unusual for varicose veins to ‘run in the family’ to some extent, but there is no well-proven genetic basis for varicose veins.

Height and weight

Although very obese people and very tall people sometimes have particularly troublesome varicose veins, no significant correlation has ever been shown between height and varicose veins, and the evidence about obesity and varicose veins is inconsistent.

Pregnancy

Varicose veins are more common in women who have had children, and the more pregnancies women have, the more likely they are to develop varicose veins. Varicose veins that develop in pregnancy are said to result partly from the pressure of the womb on the veins, but the evidence for this is poor, and relaxation of the vein walls by hormones may be more important.

Diet and bowel habit

It has been suggested that lack of fibre in the diet and sitting straining on the lavatory (rather than squatting briefly to pass a bulky stool) might predispose to varicose veins. This idea has given rise to a lot of debate, but there is no real evidence to support it.

Occupation and posture

A number of studies have found that varicose veins are more common in people who stand up at work – particularly those who stand still for long periods.

Tight clothing

There has been a traditional belief that wearing tight clothes, such as corsets, might lead to varicose veins. There is some evidence that this may be true, but it is difficult to separate the wearing of corsets from the effect of increasing age.

Why do veins become varicose?

The answer, in most cases, is that we don’t really know what causes varicose veins. There are two main theories.

‘Descending valvular incompetence’

If the valve at the top of a vein (for example, the valve at the top of the long saphenous vein in the groin) becomes ‘incompetent’ and stops working properly, this allows a head of pressure to distend the section of vein below it. This stretches the vein’s wall, making it varicose, and this makes the next valve down incompetent, and so on down the leg.

Weakening of the vein wall

There is some evidence that the amount of collagen (which gives strength) and the quality of the elastin (which gives elasticity) are abnormal in the leg veins of people who develop varicose veins. It is therefore possible that weakening of the vein wall is the cause of varicose veins, but not all the studies done on vein walls are in agreement about these changes. This theory applies to ‘primary varicose veins’ – the usual kind that develop for no very obvious reason. A very few people get ‘secondary varicose veins’ as a result of deep vein thrombosis blocking the deep veins, tumours in the pelvis pressing on the leg veins, or rare congenital problems with the arteries and veins.
 
If one valve stops working properly, this applies an abnormally high pressure on the section of vein beneath it. This pressure causes a stretching which makes the next valve down incompetent, and so on.

 

What trouble do varicose veins usually cause?

Many people with varicose veins never have symptoms of any kind from them throughout their lives. When symptoms do occur, they are generally a nuisance, rather than medically serious. Only a very small proportion of people with varicose veins ever develop ulcers or other damaging problems, and there are almost always warning signs, with darkening or eczema of the skin at the ankle.

Cosmetic embarrassment

This is by far the most common problem that varicose veins cause, and is perfectly understandable in a society that makes women want to have nice looking legs. Concern about the appearance often leads people to attribute minor symptoms in their legs to varicose veins.

Worry about future problems

Worry about the possible dangers of having varicose veins is common, and I include it among ‘symptoms’ because it is often an important reason for people seeking medical advice. Doctors need to recognise and to be sensitive to these worries, which patients are often reluctant to admit.

Aching and discomfort

Aching and heaviness of the legs are common complaints, particularly after standing up for a long time. Some people with varicose veins get itching, a feeling of heat and tenderness over their veins. All symptoms caused by varicose veins tend to be worse at the end of the day, and relieved (at least to some extent) by ‘putting your feet up’, although a few people find that their varicose veins are tender at night. There are lots of reasons that people get aches and pains in their legs, apart from varicose veins. A recent large study done in Edinburgh has shown a poor association between leg symptoms and the presence of varicose veins, especially in men. Even in women, the only symptoms that correlated strongly with the presence of varicose veins were heaviness/tension, aching and itching. Restless legs, a feeling of swelling, cramps and tingling had no significant relationship with the presence of varicose veins. This means that people with varicose veins need to realise that pains in their legs may have nothing to do with the veins, and doctors need to question patients carefully to try to work out whether their symptoms are caused by varicose veins before advising on treatment. As aching from varicose veins is usually improved by wearing good support stockings, I sometimes advise these for a trial period: this may help in deciding whether veins are the cause. All this is made more difficult because people who hate the look of their varicose veins often blame them for any symptoms in their legs.

Ankle swelling

Varicose veins can cause ankle swelling in a few people, as the pressure in the veins causes fluid to be squeezed out into the tissues as they stand, sit with their feet on the ground or walk about. The swelling goes away after a night in bed. There are many other reasons for leg swelling apart from varicose veins, and even after thorough examination it is often difficult to be certain if varicose veins are the cause. It may become clear only after varicose veins have been treated by an operation, and even then the swelling can take a long time to go away.

Varicose veins can cause more serious chronic problems

In some people abnormally high pressure in the leg veins can cause damage to the skin, and eventually lead to ulcers. This can happen as a result of varicose veins, problems in the deep veins or a combination of the two (any skin damage caused by the veins can be called venous skin problems). We do not fully understand why most people with big varicose veins never get skin trouble, whereas a few people with small varicose veins do. Venous skin damage leads to a number of different appearances.

Venous eczema (‘varicose eczema’)

The first sign of trouble is often mild eczema and itchiness of the skin – usually just above the ankle. This can be just a small patch, or a larger area. It can be settled temporarily by steroid-containing creams, but in the long term they are not a safe or satisfactory treatment, because they can cause the skin to become thin and fragile. If neglected, the eczema can become very severe, with inflamed, red, scaly skin all around the lower leg.
 
Venous eczema

Skin pigmentation

This means darkening of the skin – first to a pale brown colour, and later to a dark, shiny brown appearance (see ‘Lipodermatosclerosis’).

Atrophie blanche

This French phrase is used to describe shiny white areas of skin, which are a sign of quite advanced skin damage.

Lipodermatosclerosis

This is the proper medical term that describes damage both to the skin (‘dermato’ = to do with the skin) and to the fatty layer beneath it (‘lipo’ = to do with fat). ‘Sclerosis’ means hardening and scarring. In chronic venous disease, it is not only the skin that becomes discoloured, shiny and hard; the fat beneath also becomes hard and shrinks, so that the area finishes up ‘dented’. The whole leg just above the ankle may become thinner because of hardening and shrinkage of the fatty layer. Although ‘lipodermatosclerosis’ is the proper medical term, I usually talk about ‘skin changes’, because this is rather easier to say and to understand! (See ‘What is the mechanism of venous skin damage and ulceration?’ below).
 
Lipodermatosclerosis

Ulcers (ulceration)

This means that the skin has become broken and is slow to heal. Ulcers have a raw base which may look pink and clean, or may contain yellowish ‘slough’. Venous ulcers may be small or large: they may be painless or very painful, for reasons we do not understand at all. Although there are other reasons for ulcers around the ankle, venous disease is by far the most common cause in the Western World (see ‘What is the mechanism of venous skin damage and ulceration?’ below).
 
Ulceration

What is the mechanism of venous skin damage and ulceration?

The precise mechanism by which skin changes and ulcers develop is controversial, despite a lot of research over many years. There have been two main theories.

The ‘fibrin cuff theory’

Microscopic examination of damaged skin from the lower leg shows a ‘cuff’ of fibrin (one of the substances involved in blood clotting) around the capillaries. It was believed that this interfered with the passage of oxygen from the blood into the tissues. More recent research has suggested that this is unlikely to be the main cause of damage to the skin and fat.

The ‘white cell trapping’ theory

White blood cells (leucocytes) contain a variety of powerful substances that lead to inflammation, and that they release when stimulated to do so. Studies on the capillaries at the ankle have shown that leucocytes become ‘trapped’ there when the venous pressure is high. They stick to special receptors on the capillary walls, and may then release inflammatory substances that cause tissue damage. Over a long period this may be the cause of damage to the skin and the fatty layer beneath it.

Putting the theories together

It may be that the fibrin cuff seen in chronically damaged skin is a long-term result of the inflammation produced by white cell trapping, rather than the cause of the trouble. Despite considerable research, there is still a lot we do not understand about the mechanisms by which venous disease causes skin changes. Exactly why ulcers develop in the damaged area is not properly understood either, although it is clear that an injury such as knocking the leg may be the start of an ulcer. Once the skin has become chronically damaged, it will never return to normal, and will always be prone to poor healing and the possibility of ulceration. However, treating the underlying venous problems, or using good compression stockings, will help to stop it getting worse and becoming more vulnerable (see page 25).
 

KEY POINTS

  • There are two systems of veins in the legs: the important deep veins and the superficial veins under the skin. It is the superficial veins that become varicose
  • Normally, valves in the veins make blood flow up the leg, and the action of the muscles helps to pump it upwards
  • When veins become varicose the valves often stop working properly: blood can flow the wrong way and cause a head of pressure that makes the veins bulge on standing. This head of pressure can lead to symptoms such as aching, and occasionally to skin damage
  • Varicose veins are associated with increasing age, having
    children and Western society
  • We are still not sure why most varicose veins form: it may be because their valves become incompetent ‘from above
    downwards’, or because their walls become weakened
  • Varicose veins can cause heaviness and aching, but there are many other causes of aches and pains in the legs. The same applies to ankle swelling
  • Raised pressure in the veins as a result of incompetent valves can cause skin damage, with eczema, pigmentation (darkening) and scarring of the fat under the skin; ulcers can then develop
  • Despite a lot of research we cannot predict who will get skin changes and ulcers, and we are not certain how the skin
    damage develops