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 causes edema. 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...