Diabetes Insipidus: An Update.

The differential diagnosis of diabetes insipidus involves the distinction between central or nephrogenic diabetes insipidus and primary polydipsia. Differentiation is important because treatment strategies vary; the wrong treatment can be dangerous. Reliable differentiation is difficult especially in patients with primary polydipsia or partial forms of diabetes insipidus. New diagnostic algorithms are based on the measurement of copeptin after osmotic stimulation by hypertonic saline infusion or after nonosmotic stimulation by arginine and have a higher diagnostic accuracy than the water deprivation test. Treatment involves correcting preexisting water deficits, but is different for central diabetes insipidus, nephrogenic diabetes insipidus, and primary polydipsia.