Hypovolemic hyponatremia

Decreased total body water (TBW) and sodium, with a relatively greater decrease in sodium

Gastrointestinal losses*

Diarrhea

Vomiting

3rd-space losses*

Burns

Pancreatitis

Peritonitis

Rhabdomyolysis

Small-bowel obstruction

Renal losses

Diuretics (eg, thiazides)

Mineralocorticoid deficiency

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

Hypothyroidism

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

Cirrhosis

Heart failure

Renal disorders

Acute kidney injury

Chronic kidney disease

Nephrotic syndrome