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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