In a woman with polyuria of6L/day, which are the 2 most impoant investigations to be done -: (A) Water deprivation test, (B) Water loading, (C) Plasma and urine osmolality, (D) Plasma osmolality
Answer is A. fluid deprivation test to differentiate which type of DI. If it is not significant administration of desmopressin required ( Harrison 17 pg 2219)