Serum and Urine Osmolalities in the Differential Diagnosis of Polyuric States

Abstract

A simple, safe and standardized overnight 8-hr water deprivation test is described for differentiating diabetes insipidus, due to either antidiuretic hormone (ADH) lack or renal tubular disease, from psychogenic polydipsia by means of the measurement of serum and urine osmolalities. The diagnosis in the patients was first made by performing a standard intravenous hypertonic sodium chloride infusion test and measuring its effect on urine flow. No overlap in either urine or serum osmolalities was apparent between normals and those with organic diabetes insipidus in the subjects examined in this series.