Disorders of Water Balance: Physiology
In this chapter, we will discuss how plasma osmolality and water balance are maintained. Like Na+ balance, water balance is determined by the amount of water that is ingested and excreted. Therefore, water intake equals water loss. In a normal individual, the major source of water intake is oral fluids. Water is also derived from other sources such as solid foods and intermediary metabolism. Intravenous fluids form the principal source of water intake in hospitalized patients. Dialysis patients may also gain water during treatments.