Hypotonic Water Overload (Water Intoxication)

How to Cite This Chapter: Panju M, Merali Z, Srivaratharajah K, Mathew A, Kokot F, Franek E, Drabczyk R. Hypotonic Water Overload (Water Intoxication). McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. https://empendium.com/mcmtextbook/chapter/B31.II. Accessed April 24, 2024.
Last Updated: January 18, 2022
Last Reviewed: January 18, 2022
Chapter Information

Definition, Etiology, PathogenesisTop

Hypotonic water overload is an increase in body water content relative to body sodium content, which leads to hyponatremia and reduced effective osmolality of body fluids.

The most frequent causes are impaired renal excretion of free water due to renal failure (acute kidney injury or chronic kidney disease) or increased antidiuretic hormone (ADH) secretion caused by nonosmotic factors (this leads to hypotonic hyponatremia with hypervolemia). The most frequent precipitating factor is the administration of electrolyte-free fluids in patients with renal failure. A rare cause of hypotonic water overload is excessive water intake by a person with normal renal function (primary polydipsia).

Clinical FeaturesTop

Manifestations are a result of excess body water (peripheral edema, effusions into body cavities) and possibly cerebral edema (as a consequence of the hypotonicity of the extracellular fluid).

Diagnosis Top

Diagnosis is based on the presence of clinical features of water overload accompanied by hyponatremia and serum hypo-osmolality, which are most frequently present in patients with conditions predisposing to this type of water overload.


The management is similar to hyponatremia with hypervolemia. The rate of correction of chronic hyponatremia must be carefully controlled.Evidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). Low Quality of Evidence (low confidence that we know true effects of the intervention). Quality of Evidence lowered due to the risk of bias from the observational nature of supporting evidence. Verbalis JG, Goldsmith SR, Greenberg A, Schrier RW, Sterns RH. Hyponatremia treatment guidelines 2007: expert panel recommendations. Am J Med. 2007 Nov;120(11 Suppl 1):S1-21. PMID: 17981159.

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