Edema is an excessive accumulation of fluid in extracellular spaces. It may be manifest, i.e., felt and seen; occult, located in the viscera; or latent, only demonstrable by chemical means. It may be local, as in inflammation or urticaria, or general and part of a systemic disturbance, as in congestive cardiac failure or nephritis.
Edema fluid may accumulate to the point where it interferes mechanically with tissue function or nutrition, so that what is at first an annoying sign of disease may later cause disability and death. Modes of relief of edema have therefore interested clinicians since the beginning of historic time. Since successful treatment depends primarily on identification and correction of the faulty mechanism, it is based largely on an understanding of physiology.
The purpose of the reports of which this is one is to review (I) mechanisms of edema formation, (II) clinical manifestations and consequences of edema, and (III) means of treatment.
The water of a unicellular organism lies within the cell; that of a multicellular organism is partitioned into intracellular and extracellular compartments. During life the membranous cell wall which separates intracellular and extracellular fluids is extraordinarily selective, so that these two fluids, although in constant shift and osmotic equilibrium, are chemically very different. Intracellular water is rich in salts of potassium; extracellular fluid has little potassium and much sodium, approximately 6 Gm. sodium chloride and 2 Gm. sodium bicarbonate per liter. The death of cells, as from burns, destroys membrane selectivity, so that sodium. . .