Hyponatremia is serum sodium concentration <135 mEq/L due to failure of normal water excretion.

Most common causes are medication effects, fluid retention and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Volume status should be assessed to help determine the underlying cause.

Commonly, patients with hyponatremia are asymptomatic and it is only an incidental finding.


Hyponatremia References

  1. Braun MM, Barstow CH, Pyzocha NJ. Diagnosis and management of sodium disorders: hyponatremia and hypernatremia. Am Fam Physician. 2015 Mar;91(5):299-307. PMID: 25822386
  2. Dineen R, Hannon MJ, Thompson CJ. Hyponatremia and hypernatremia. In: Jameson J, De Groot L, de Kretser D, et al. Endocrinology: Adult and Pediatric: Saunders, Elsevier; 2016.
  3. Gross P. Clinical management of SIADH. Ther Adv Endocrinol Metab. 2012 Apr;3(2):61-73. doi: 10.1177/2042018812437561. PMID: 23148195
  4. Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Eur J Endocrinol. 2014 Feb;170(3):G1-G47. doi: 10.1530/EJE-13- 1020. PMID: 24569125
  5. Sterns RH. Diagnostic evaluation of adults with hyponatremia. UpToDate. https://www.uptodate.com. Jan 2019.
  6. Sterns RH. Overview of the treatment of hyponatremia in adults. UpToDate. https://www.uptodate.com. Jan 2019.
  7. Tee K. The suspect – SIADH. Australian Journal of General Practice. 2017 Sep;46(9). https://www.racgp.org.au.
  8. Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013 Oct;126(10)(Suppl 1):S1-S42. doi: 10.1016/j.amjmed.2013.07.006. PMID: 24074529
  9. Myint KS, Tisdale MM, Chetcuti S, et al. Joint trust guideline for inpatient management of hyponatremia. Norfolk and Norwich University Hospitals (NHS) Foundation Trust. http://www.nnuh.nhs.uk/. 12 Oct 2019.
  10. Seay NW, Lehrich RW, Greenberg A. Diagnosis and management of disorders of body tonicity - hyponatremia and hypernatremia: core curriculum 2020. Am J Kidney Dis. 2020 Feb;75(2):272-286. doi: 10.1053/j.ajkd.2019.07.014. PMID: 31606238
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