Lymphedema is the swelling of tissues (edema), usually in the feet and legs,due to lymphatic obstruction.

Lymphatic fluid seeps out of the blood circulation into the tissues. It returns to the heart through separate channels called lymphatics, carrying waste products and germs. On its way to the heart, it passes through lymph nodes, where infecting germs (including some cancers) are attacked by the body's defense mechanisms.

If lymphatic channels are obstructed or inadequate, fluid backs up and causesedema. Tissue fluid can also return to the circulation through tissues, without using the lymphatics, but gravity hinders this flow. So lymphedema is usually confined to the feet and legs.

There are several types of congenital abnormalities associated with other birth defects of the lymphatics, which cause this condition. One in 10,000 people have this type of lymphedema.

Lymphatics can be damaged or obstructed by many different agents. Repeated bouts of blood poisoning can scar the vessels. Surgery to remove cancerous lymph nodes or radiation therapy can damage them. Cancer itself, as it invades the lymph system, as well as several other infectious and inflammatory conditions, can result in blockage of lymph flow. The most common worldwide cause oflymphedema is a group of worms known as filaria. Filaria can be found in mostof the developing regions of the world. They enter humans through insect bites, mostly mosquitoes, and take up residence in lymphatic channels, irritating them enough to scar them and impair their ability to carry lymph. Long-standing lymphatic filariasis can cause massive swelling of the legs, earning thename elephantiasis.

Since other types of swelling may look similar to lymphedema, precise diagnostic tools must be used. Ultrasound, computed tomography scans (CT), and magnetic resonance imaging (MRI) scans may help with diagnosis. Lymphangiography may be needed to clarify the cause.

Physical activity can pump some of the fluid out of the tissues. Compressionstockings are of some value, as are devices that actively squeeze fluid out of tissues. Diuretics may alleviate some of the edema. Because the ability ofthe skin to defend itself is hampered by the swelling, infections are more common. It is therefore important to care for wounds and to treat infections early.

When caused by infection, lymphedema can be treated by eliminating the underlying infection with antibiotics.

Reconstructing lymphatic channels using microvascular surgery has recently achieved some success.

If congenital, lymphedema is a progressive and lifelong condition. If secondary or caused by an underlying disease or infection, lymphedema can be treatedby treating the disease.

When traveling in regions known to have filaria, avoidance of insect bites iscrucial. Prompt and effective treatment of the infection will prevent the consequences.

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