Osmolality - urine
Last updated: Monday, 22, March, 2004
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| Item | Process |
|---|---|
| Specimen | Random urine specimen, without preservative. |
| Method | Freezing point depression or vapour pressure depression. |
| Reference Interval | Physiological range: 50-1,200 mmol/kg. |
| Application | Renal disease, SIADH, and polyuric syndromes. |
| Interpretation | The kidneys can normally concentrate urine to an osmolality of >800 mmol/kg within 12 hours of fluid restriction (water deprivation test). Comparison of serum and urine osmolalities may help to determine the cause of polyuria, to diagnose SIADH and to distinguish 'pre-renal' from 'renal' causes of impaired renal function. See Osmolality - serum. |
| Reference | Wong LL and Verbalis JG. Endocrinol Metab Clin North Am 2002; 31(1): 121-140. |