Which water deprivation test findings are diagnostic for central or nephrogenic diabetes insipidus (DI)?

Updated: Mar 18, 2020
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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Answer

In healthy individuals, water deprivation leads to a urinary osmolality that is 2-4 times greater than plasma osmolality. Additionally, in normal, healthy subjects, administration of ADH produces an increase of less than 9% in urinary osmolality. The time required to achieve maximal urinary concentration ranges from 4-18 hours.

In central and nephrogenic DI, urinary osmolality will be less than 300 mOsm/kg after water deprivation. After the administration of ADH, the osmolality will rise to more than 750 mOsm/kg in central DI but will not rise at all in nephrogenic DI. In primary polydipsia, urinary osmolality be above 750 mOsm/kg after water deprivation. A urinary osmolality that is 300-750 mOsm/kg after water deprivation and remains below 750 mOsm/kg after administration of ADH may be seen in partial central DI, partial nephrogenic DI, and primary polydipsia. [31]


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