Hypernatremia - Differential Diagnosis Workup Algorithm



1) Check Urine Osmolality:

 > 600 mOsm/kg - Implies extrarenal mechanism

 ≤ 600 mOsm/kg - Implies renal mechanism



2) Volume Status



Extrarenal Hypernatremia:

 • Hypovolemic (H2O loss): GI loss, Skin loss

 • Euvolemic (Low H2O intake): Impaired thirst, Lack of access to H2O

 • Hypervolemic (Excess salt intake): Iatrogenic, Ingestion



Renal Hypernatremia:

 • Hypovolemic: Diuretics, osmotic (solute) diuresis

 • Euvolemic: Diabetes insipidus (central or nephrogenic)

 • Hypervolemic: Conn syndrome, Cushing syndrome



Matthew Ho, MD PhD @MatthewHoMD



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