What are varicose veins?
Varicose veins are dilated (enlarged) sections of veins which are located just under the surface of the skin – usually on the leg. They are often easy to see, as they look thick and 'knobbly'. They may be less obvious if you are overweight, as they are hidden by fatty tissue under the skin.
Other, smaller types of veins which can be noticeable, are: 'reticular veins' - a closely grouped network of small veins; and 'thread veins' or 'spider veins', which look like a kind of starburst pattern on an area of the leg. These are not true varicose veins.
What causes varicose veins?
It is thought that the wall of the vein becomes 'weak' in some sections of one or more veins. This section of the vein then dilates (widens) and become more prominent. If this occurs near a valve then the valve may become 'leaky' and blood may flow backwards.
Once this happens at one valve there is extra pressure of blood on the next valve down. A combination of a slightly weak wall and extra pressure of blood may then cause the lower valve to become leaky too, and so on. This process can take a long time, but may gradually progress along the length of a vein. Blood then 'pools' in the enlarged vein and makes it stand out.
Who develops varicose veins?
About 3 in 10 adults develop varicose veins at some time in their life. Most people with varicose veins do not have an underlying disease and they occur for no apparent reason. However, the chance of them developing is increased with:
- Pregnancy. This is partly due to the baby causing extra pressure on the veins, and partly because hormones you make during pregnancy tend to relax vein walls. The more babies you have, the more the risk of permanent varicose veins developing. Varicose veins tend to appear, or get worse, during pregnancy, but often improve after childbirth when the pressure on the veins eases.
- Age. They are more common with increasing age.
- Being overweight, which appears to increase the chance for women but not men.
- Standing lots. Jobs which involve lots of standing are often said to cause varicose veins. However, there is little scientific evidence to support this theory.
Sometimes an underlying disease may cause varicose veins, for example:
- A previous blood clot (thrombosis) or injury in a deep leg vein.
- Rarely, a swelling or tumour in the pelvis (lower part of the tummy) which blocks flow in the veins at the top of the leg.
- Very rarely, varicose veins are due to abnormal blood vessels - if some of the veins or arteries have not formed in the normal way.
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