Urine chemistry tests for the diagnostic evaluation of a patient with polyuria

UOsm <100 mOsm/Kg (H2O diuresis)

 • Primary polydipsia

 • Diabetes insipidus (central or nephrogenic)

UOsm >300 mOsm/Kg

 • 2 × (Na + K) = UOsm - Salt and water diuresis (intravenous fluids)

 • 2 × (Na + K) << UOsm - Osmotic diuresis

    - Glucose (uncontrolled diabetes mellitus)

    - Urea

    - ↑Protein intake (supplements, parenteral)

    - ↑Catabolism

    - Mannitol



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