[Systemic edema in kidney diseases].

Extracellular fluid expansion states are characterized by increase total body water. These disorders are usually associated with avid renal sodium and water retention. Some examples of such abnormal sodium retention in renal diseases are acute glomerulonephritis and nephrotic syndrome. Edema formation in case of acute glomerulonephritis is primarily responsible for salt retention. On the other hand, the pathogenesis of edema in nephrotic syndrome involves two different mechanisms those are underfill and overfill hypothesis. According to the underfill hypothesis, nephrotic syndrome results in increase of urinary loss of albumin, which subsequently leads to hypoalbuminemia and decreased plasma osmotic pressure. Overfill theory explains that renal salt and water retention is primary phenomenon that leads to plasma volume expansion and subsequent exudation of fluid to the interstitium.