Lymphoedema is swelling (oedema) in the tissues beneath the skin which occurs when lymph can't drain away.
Lymphoedema can affect any part of the body including the head, neck and genitals. However, it most commonly affects a limb and sometimes the adjoining area of the trunk and/or breast.
The lymphatic system
The lymphatic system is made up of organs, such as the tonsils, thymus and spleen, and a network, of nodes (glands) and vessels (tubes), which extend throughout the body. The lymphatic vessels contain fluid called lymph.
Lymph is a colourless fluid that forms in the tissues of the body. It normally drains back into the blood circulation through a network of vessels and nodes. Lymph nodes act as filters removing dead or abnormal cells, including cancer cells and bacteria, playing an important part in the body's defence against infection. The number of lymph nodes in the body ranges from 500 to 1500. They are found in clusters in the head and neck region, under-arms (axillae), groin, pelvis and abdomen.
As lymph returns to the circulation, it filters through these nodes draining into larger lymph vessels in the body which then join the main circulation. This constant flow balances the amount of fluid in different parts of the body. The lymphatic system also makes cells called lymphocytes, which help the body fight infections. Lymphocytes also circulate in the blood, but are concentrated in the lymph, which forms part of the body's defence system.
When does lymphoedema occur?
Lymphoedema may be inherited as it can run in families. It can be due to under-development of the lymphatic system that can be evident at birth but may not show up until later in life. Sometimes it may occur without any family history and with no other obvious cause. This is called primary lymphoedema.
More commonly lymphoedema may develop following an operation or radiotherapy to areas of the body where lymph nodes are present to treat cancer. It may occur immediately after treatment or many years later. It can also occur as a result of infection or trauma. This is called secondary lymphoedema.
What causes lymphoedema?
Lymphoedema may appear when lymph vessels or lymph nodes are affected as a result of cancer treatment. Following surgery or radiotherapy to lymph node areas, scar tissue is formed and lymph drainage routes from part of the body may be reduced.
The situation is similar to that of a river, which has been dammed. Water builds up behind the dam, overflows the banks of the river and, if the ground doesn't drain properly, it becomes waterlogged. In lymphoedema, flow of lymph is reduced through the scar tissue and builds up in the surrounding tissues causing the area to become swollen.
Lymphoedema may develop after surgery or radiotherapy to treat cancer. It may affect a limb or any other part of the body.
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