Causes of Hyponatremia - Differential Diagnosis Algorithm

Hypovolemia, UNa > 20: 

 • Renal losses, Diuretic excess, Mineral corticoid deficiency, Salt-losing deficiency, Bicarbonaturia with renal tubal acidosis and metabolic alkalosis, Ketonuria, Osmotic diuresis, Cerebral salt wasting syndrome

Hypovolemia, UNa < 20: 

 • Extrarenal losses, Vomiting, Diarrhea, Third spacing of fluids, Burns, Pancreatitis, Trauma

Euvolemia, UNa > 20: 

 • Glucocorticoid deficiency, Hypothyroidism, Stress, Drugs, Syndrome of inappropriate antidiuretic hormone secretion

Hypervolemia, UNa > 20:

 • Acute or chronic renal failure

Hypervolemia, UNa < 20

 • Nephrotic syndrome, Cirrhosis, Cardiac failure



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