Figure 1

The lymphatic system comprises a network of tiny pipes with tinier valves that function to clear the interstitial tissue spaces of excess water, large molecules, and particulate matter (tiny particles). This matter is transported through filters (lymph nodes) from the tissues back into the blood circulation by way of the veins. A large proportion of plasma proteins passes through blood capillary walls from the circulation. The lymphatic system's job is to absorb these proteins and clear them. If the lymphatic system fails to do this, plasma proteins accumulate in the interstitial fluid. This increases pressure there, and more water moves into the interstitial space, resulting in fluid retention, which is lymphedema.

Lymphedema is the accumulation of tissue fluid in interstitial spaces, mainly tissues under the skin. It is the result of an overload of fluid not cleared by the lymphatic system. Unfortunately, lymphedema is a poorly understood, lifelong condition.

There are three forms of lymphedema. The most common (80%) is a slowly progressive swelling in the feet, ankles, and lower legs in women, beginning at puberty. This is primary lymphedema, which means that the cause originates in the lymphatic system. Swelling does not limit activity at first, but later the size and weight of the limb cause disability in addition to disfigurement (Figure 1). There may be a family history of lymphedema. Often there is slight lymphedema in the opposite limb.

Figure 1. Progressive lymphedema is disfiguring and disabling. (From Gloviczki P, Yao, JST, eds. Handbook of Venous Disorders, 2nd ed. London: Arnold, 2001:454, Fig. 45.2.)

The most common form of lymphedema is primary lymphedema (90% of all cases).  A much less common form of primary lymphedema is entirely hereditary. It affects one or more limbs and is seen at birth or at a young age. It is associated with lymph blisters in the skin.

Figure 2

Secondary lymphedema has a direct cause that does not originate in the lymphatic vessels or lymph nodes. Less common than primary lymphedema (10%), secondary lymphedema affects the entire leg or other part quickly, within 6-8 weeks. It may result from an insect bite, an infection, blunt trauma, mastectomy (surgical removal of cancerous breast; Figure 2), parasites, or surgical removal of lymph nodes for cancer treatment.

Figure 2. Lymphedema in a patient's arm after radical mastectomy. (From Gloviczki P, Yao, JST, eds. Handbook of Venous Disorders, 2nd ed. London: Arnold, 2001:454, Fig. 45.3.)