To understand lymphedema, you need to know a little about the lymphatic system.
The lymphatic system is a series of vessels (similar to veins) that are just under the skin and connect to the lymph nodes in the neck, underarms and groin. The lymph vessels act like a flushing system, throughout the bodyand picking up waste products, bacteria, dead cells and large protein molecules and carrying them to the lymph nodes. The lymph nodes then perform the task of cleaning and recirculating the fluid. (That's why, when you are seriously ill, you may feel a pain or have a swelling in the neck, underarms or groin as the nodes try to fight the cause of the illness.)
However, unlike the blood system, the lymphatic system doesn't have a pump, but relies on the movement of tissue to squeeze lymphatic fluid through the system and around the body.
The lymphatic system plays an integral role in the immune functions of the body. It is the first line of defense against disease. This network of vessels and nodes transports and filters lymph fluid containing antibodies and lymphocytes (good) and bacteria (bad). The body's first contact with these invaders signals the lymphatics, calling upon this system to orchestrate the way the infection-fighting cells prevent illness and diseases from invading micro-organisms. If the lymph nodes are unable to circulate the fluid in an area of the body, that area will swell with the protein rich fluid - this is lymphedema.
Once lymphedema occurs, the swelling is likely to increase, and it's important to get therapy as soon as possible.