High flow failure of the lymph circulation.

The partition of extracellular fluid between plasma and tissue is determined by the balance of hydrostatic and oncotic pressure gradients across capillary membranes, and a filtration coefficient reflecting the surface area and permeability of filtering capillaries. Normally, a small excess of tissue fluid forms, enters lymphatics and returns to the bloodstream. In health, lymph formation and lymph absorption are exactly in balance and tissues are edema free’ (Figure 1). When lymphatic channels, however, are congenitally absent, or become obstructed or obliterated plasma that normally escapes from the bloodstream accumulates in tissues or body cavities as protein-rich edema fluid. This phenomenon is referred to as &dquo;lymphedema&dquo; and is characterized by a decreased rate of lymph absorption or &dquo;low output failure&dquo; of the lymph circulation’ (Figure 2). On the other hand, when lymph formation is increased to the point where it overwhelms the capacity of the lymphatic absorptive apparatus, albeit a nondiseased one, edema and/or effusion also result’ (Figure 3). This other form of &dquo;lymphedema&dquo; characterized by excess lymph formation or &dquo;high output failure&dquo; of the lymph circulation forms the basis of this report.