EDEMA

EDEMA

Approximately 60% of lean body weight is water, two-thirds of which is intracellular and the remainder is in extracellular compartments, mostly as interstitial fluid; only 5% of total body water is in blood plasma. The term edema signifies increased fluid in the interstitial tissue spaces; fluid collections in different body cavities are variously designated hydrothorax, hydropericardium, or hydroperitoneum (the last is more commonly called ascites). Anasarca is a severe and generalized edema with profound subcutaneous tissue swelling.

Edema is extravasation of fluid from vessels into interstitial spaces; the fluid may be protein poor (transudate) or may be protein rich (exudate).Edema results from any of the following conditions:

Increased hydrostatic pressure, caused by a reduction in venous return (as in heart failure)Decreased colloid osmotic pressure, caused by reduced concentration of plasma albumin (due to decreased synthesis, as in liver disease, or increased loss, as in kidney disease)Lymphatic obstruction that impairs interstitial fluid clearance (as in scarring, tumors, or certain infections)Primary renal sodium retention (in renal failure)Increased vascular permeability (in inflammation)