What is the pathophysiology of hyponatremia?

Updated: Jun 17, 2019
  • Author: Eric E Simon, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Hypoosmolality (serum osmolality < 280 mOsm/kg) always indicates excess total body water relative to body solutes or excess water relative to solute in the extracellular fluid (ECF), as water moves freely between the intracellular and the extracellular compartments. This imbalance can be due to solute depletion, solute dilution, or a combination of both.

Under normal conditions, renal handling of water is sufficient to excrete as much as 15-20 L of free water per day. Further, the body's response to a decreased osmolality is decreased thirst. Thus, hyponatremia can occur only when some condition impairs normal free water excretion. [3]

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