Table 2.

The response of serum and urine osmolality, and urine output to a single dose of desmopressin. Significant polyuria and polydipsia, which accompanied high serum osmolality and inappropriately low urine osmolality, did not respond at all to parenteral desmopressin. This was diagnostic of NDI. The criteria for diagnosing NDI were: urine output >3 l/day; urine osmolality <300 mosmol/kg; failure to concentrate urine when serum osmolarity >295; and inability to concentrate urine after desmopressin.⁷