ABSTRACT

Central diabetes insipidus (CDI) is a water homeostasis disorder characterized by an inability to concentrate urine because of insufficient production of antidiuretic hormone. Dehydration with hypernatremia can occur during the neonatal period in preterm neonates in association with insensible water loss, high urine output, and reduced sodium excretion. A high index of suspicion is required to diagnose CDI in preterm neonates. We report two cases, who presented persistent hypernatremia with polyuria despite increased fluid supply and low sodium intake. CDI diagnosis was confirmed by the therapeutic test with oral vasopressin analog. Investigations were all normal; CDI was considered idiopathic. Persistent hypernatremia despite increased fluid intake with polyuria, hyposthenuria, low urine output, and high plasma osmolality is the key point for the diagnosis.