Hyponatremia is a topic covered in the Diagnosaurus.

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Isotonic hyponatremia or pseudohyponatremia (normal serum osmolality; artifact corrected in most U.S. labs)

  • Hyperlipidemia
  • Hyperproteinemia
Hypertonic hyponatremia (serum osmolality >295 mosm/kg)
  • Hyperglycemia
  • Mannitol, sorbitol, glycerol, maltose
  • Radiocontrast agents
Hypotonic hyponatremia (serum osmolality < 280 mosm/kg)Hypovolemic
  • Extrarenal salt loss (UNa+ < 10 meq/L): dehydration, diarrhea, vomiting
  • Renal salt loss (UNa+ >20 meq/L): diuretics, ACE inhibitors, nephropathies, mineralocorticoid deficiency, cerebral sodium-wasting syndrome
  • Syndrome of inappropriate secretion of antidiuretic hormone (SIADH)
  • Postoperative hyponatremia
  • Hypothyroidism
  • Psychogenic polydipsia
  • Beer potomania
  • Idiosyncratic drug reaction (thiazides, ACE inhibitors)
  • Endurance exercise
Hypervolemic (edematous states)
  • Congestive heart failure
  • Liver disease
  • Nephrotic syndrome (rare)
  • Advanced renal failure

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Last updated: December 1, 2014