Simplifying the diagnosis of diabetes insipidus in children
R. A. Richman, E. M. Post, D. D. Notman, Z. Hochberg and A. M. Moses
We simplified the procedures for identifying children with diabetes
insipidus by using the relationship between urine and plasma osmolality
(Uosm and Posm). We defined the normal Uosm-Posm relationship as the area
within the 95% confidence regions for pairs of osmolality measurements
obtained from normal children during periods of free access to fluids and
after oral hydration. In 13 patients with diabetes insipidus, Uosm-Posm
coordinates were outside these regions in 50 of 64 pairs (one to ten per
patient) during periods of free access to fluids. After three hours of
fluid deprivation, the Uosm-Posm relationship was abnormal in 12 patients;
the 13th was unable to void. For those with a normal Posm, and Uosm less
than Posm, another pair of osmolality measurements after three hours of
fluid restriction should determine the diagnosis.
