[Regulation of sodium and water balance by the kidney]

Maintenance of consistent internal environment is essential for mammalians to survive in waterless circumstances. Extracellular fluid (ECF) volume is maintained within a narrow range in normal humans, despite day-to-day variations in the dietary intake of salt and water. In general, kidneys are the major organs that play a predominant role in the control of the fluid and electrolyte balance. Recent advances in the molecular biology have provided significant contribution to the identification of kidney specific channels and transporters for sodium and water, leading to better understandings of the regulation of sodium and water balance. Generalized edema formation, a clinical hallmark of ECF volume expansion, represents the accumulation of excessive fluid volumes in the interstitial compartment and is invariably associated with renal sodium retention. In this article, we review the regulation of sodium and water balance in the kidney to understand the renal mechanisms of edema formation.