How does syndrome of inappropriate antidiuretic hormone secretion (SIADH) affect urinary loss of Na+?

Updated: Aug 16, 2019
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

In SIADH, urinary loss of Na+ continues despite significant hyponatremia. In these patients, as in healthy patients, urinary Na+ excretion is a reflection of Na+ intake and, therefore, usually is greater than 20 mmol/L. However, in the setting of Na+ restriction in patients with SIADH or in patients with volume depletion due to extrarenal losses, the urinary Na+ concentration may be very low.


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