Lymphedema is a chronic, incurable condition that is characterized by an abnormal collection of fluid owing to an anatomical alteration of the lymphatic system.1 Throughout the world, it is estimated that one person in 30 is afflicted with lymphedema.2 Lymphedema can lead to significant impairments in function, integumentary disorders, pain, and psychological issues. Appropriate identification of this disease can allow intervention and improve functional and aesthetic outcomes and patient quality of life. This chapter will describe the function of the lymphatic system and the etiologies of lymphedema. Examination, intervention, and preventive measures will be discussed, as well as impairments associated with lymphedema, including loss and restoration of function and other complications involving the integument.
The lymphatic system has two main functions. The first is to provide significant immune function by protecting the body from disease and infection via production, maintenance, and distribution of lymphocytes. The second function is the facilitation of fluid transport from the interstitial tissues back into the bloodstream. This fluid transport maintains normal blood volume and eliminates chemical imbalances in the interstitial fluid.3 The substances transported by the lymphatic system are called lymphatic loads and consist of protein, water, cellular debris, and fat (from the digestive system). These lymphatic loads are filtered by regional and central lymph nodes prior to reentry into the venous blood system.
The lymphatic capillaries, the beginning of the lymphatic system, abound in the dermis at the dermal-epidermal junction, forming a continuous network over the entire body, with the exception of the central nervous system (CNS) and cornea.3 (Fig. 18.1) Unlike blood capillaries that consist of continuous tubules of endothelial cells, lymphatic capillaries consist of overlapping endothelial cells. A surrounding fiber net of anchoring filaments, arranged around the lymph capillaries, enables these vessels to stay open even under high tissue pressure.4 (Fig. 18.2) The lymphatic loads are collected by the lymph capillaries and flow into bigger lymph vessels called precollectors, which then drain into collectors. Lymph collectors have segments called lymph angions, which are the sections between two valves in a lymph collector. Valves are spaced every 6 to 20 mm, and the frequency of contraction of lymph angions at rest is 6 to 10 contractions per minute.5 The contraction of smooth muscle in each angion (called lymphangiomotoricity) generates the propulsive force of lymph flow along the lymph vessel. This is aided by a large number of valves inside the collectors, which enable the one-way flow of lymph. The propulsion directs the lymph fluid into regional and central lymph nodes to be filtered. (Fig. 18.3) Ultimately, the lymph fluid empties into the venous system through the left and right venous angles. The left and right venous angles are junctions between the subclavian and jugular veins at the level of the clavicles.