Fig. 5.18 
The interpretation of results from the water deprivation test. 
Results of many polyuric patients fall into the urine osmolality ranges of 300–750mosmol/kg after dehydration and to less than 750mosmol/kg after administration of desmopressin. The test therefore. often fails to distinguish between partial forms of cranial diabetes insipidus (CDI) and nephrogenic diabetes insipidus (NDI) and primary polydipsia (PP).