Principal Causes of Hyponatremia
Mechanism | Category | Examples |
|---|---|---|
Hypovolemic hyponatremia | ||
Decreased total body water (TBW) and sodium, with a relatively greater decrease in sodium | Gastrointestinal losses* | Diarrhea Vomiting |
3rd-space losses* | Peritonitis | |
Renal losses | Diuretics (eg, thiazides) Osmotic diuresis (glucose, urea, mannitol) Salt-losing nephropathies (eg, interstitial nephritis, medullary cystic disease, partial urinary tract obstruction, polycystic kidney disease) | |
Euvolemic hyponatremia | ||
Increased TBW with near-normal total body sodium | Medications | 3,4-Methylenedioxymethamphetamine (MDMA [ecstasy]) |
Endocrine disorders | Adrenal insufficiency as in Addison disease Syndrome of inappropriate antidiuretic hormone (ADH) secretion | |
Increased intake of fluids | Primary polydipsia | |
States that increase nonosmotic release of vasopressin(ADH) | Emotional stress Nausea Pain Postoperative states | |
Hypervolemic hyponatremia | ||
Increased total body sodium with a relatively greater increase in TBW | Extrarenal disorders | |
Renal disorders | ||
* Gastrointestinal and 3rd-space losses cause hyponatremia if replacement fluids are hypotonic compared with losses. | ||