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What is Lymphoedema?
by: J.R. Casley-Smith & Judith R. Casley-Smith (L.A.A., University of Adelaide)

Lymphoedema (lymphedema) occurs when the lymphatic system does not work properly. This results in the long-term swelling of part or parts of the body.
The Lymphatic System
The lymphatic system is similar to the blood system and has just as many vessels - but they contain lymph, which is clear and so cannot be seen (unless a suitable dye is injected). The lymphatics differ from the blood system in that the blood continually circulates through each part of the body while the lymph just drains from each part.

Lymphatics drain away the excess protein and water which continually escape from the blood in small amounts, plus some substances made in the tissues, and any foreign substances which enter them. Lymphatics start, in almost every tissue, as many tiny vessels which gradually join together into bigger ones.

Lymph is pumped into and along these vessels by the movements of adjacent muscles and by the contractions of the walls of the larger lymphatics. This pumping is aided by many valves inside the vessels. Finally the lymphatic system empties into the blood (largely in the lower neck).

On its way along the lymphatics, the lymph is filtered in the lymph nodes (lymph glands). These remove foreign matter (e.g. bacteria) and start any necessary immune reactions.
Oedema (Edema)
The lymphatics help to remove the excess fluid and protein which enters the tissues from damaged blood vessels, in any inflammation (e.g. after a burn, or other injury). If they cannot remove it all, the part swells (oedema, edema). However this swelling is usually only temporary, because the tissues heal and the blood vessels no longer leak excessively.

In an acute injury, e.g. a sprained ankle, the lymphatics are essentially normal. Although there is initial swelling, this is gradually removed over days to weeks. The overload is only temporary although, depending on the severity of the injury, some fibrosis will occur. This may remain for months or even permanently.
Lymphoedema (Lymphedema)
However if the lymphatic system is damaged or blocked, protein continues to enter the tissues from the blood capillaries in the normal way, and a build-up occurs in the tissues the lymphatics should be draining. The accumulation of protein in the tissues causes excess fluid to enter them and the tissues to swell. The swelling decreases the oxygenation of the tissues, interferes with their normal functioning, and makes them heal more slowly than normal.

To some extent, the protein is also removed by some of the cells in the tissues (e.g. the macrophages). These assist the lymphatic system and can partly take over its role if it is blocked. However in lymphoedema, the chronic excess protein causes these cells also to cease to function.

The excess protein also acts as a stimulus for chronic inflammation. One of the results of this is the formation of much excess fibrous tissue. The chronic inflammation causes more blood capillaries to form and to be dilated. This makes the limb feel hot.

This heat, combined with the stagnant protein provides a perfect site for bacterial growth (Secondary Acute Inflammation, S.A.I. or dermato-lymphangio-adenitis, D.L.A.). The patient may be very ill, with constant infections, and need hospitalisation. Fungal infections are also very frequent, and are often difficult to clear up. These infections, themselves, place greater loads on the lymphatics, and so worsen the lymphoedema. Any infection or other inflammation (e.g. after injury, sunburn, etc.) makes the lymphoedema worse.

If the swelling is rapid (e.g. after an operation), it can cause great pain. This is because the tissues are being torn apart. Adjacent areas, which are receiving excess lymph diverted from the blocked region, also often ache (e.g. the shoulder adjacent to a lymphoedema

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