What is the role of water deprivation testing in the workup of 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

The water deprivation test (ie, the Miller-Moses test), a semiquantitative test to ensure adequate dehydration and maximal stimulation of ADH for diagnosis, is typically performed in patients with more chronic forms of DI. The extent of deprivation is usually limited by the patient’s thirst or by any significant drop in blood pressure or related clinical manifestation of dehydration.

With mild polyuria, water deprivation can begin the night before the test. With severe polyuria, water restriction is carried out during the day to allow close observation.

All water intake is withheld, and urinary osmolality and body weight are measured hourly. When 2 sequential urinary osmolalities vary by less than 30 mOsm/kg or when the weight decreases by more than 3%, 5 U of aqueous ADH or desmopressin are administered subcutaneously. A final urine specimen is obtained 60 minutes later for osmolality measurement.


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