What is the diagnostic criteria for syndrome of inappropriate ADH secretion (SIADH)?

Updated: Jun 17, 2019
  • Author: Eric E Simon, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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The diagnostic criteria for SIADH are as follows:

  • Normal hepatic, renal, and cardiac function - clinical euvolemia (absence of intravascular volume depletion)

  • Normal thyroid and adrenal function

  • Hypotonic hyponatremia

  • Urine osmolality greater than 100 mOsm/kg, generally greater than 400-500 mOsm/kg with normal renal function

Urinary sodium concentrations are also typically greater than 20 mEq/L on a normal salt diet as sodium excretion will reflect dietary sodium intake. Serum uric acid levels are generally reduced; this is due to reduced tubular uric acid reabsorption, which parallels the decrease in proximal tubular sodium reabsorption associated with central volume expansion. These findings are also found in a renal salt wasting process. This similarity makes the differentiation between salt wasting and SIADH difficult except that in renal wasting, one would expect to find a hypovolemic state.

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