What kind of condition is diabetes insipidus (d.i.)?

Serious dehydration: Congenital and secondary diabetes insipidus is a rare inherited or acquired disease in which patients suffer serious dehydration as the result of an inability of their kidneys to produce a concentrated urine.

Missing ADH (vasopressin): Anti diuretic hormone helps concentrate the urine to keep the body's sodium and water levels balanced. If the brain does not make enough ADH (vasopressin) or of the kidney ignores the adh, (vasopressin) a person can urinate too much dilute urine, becoming hypernatremic (high sodium) and dehydrated. Can be genetic, due to head trauma, brain tumor, infection, anorexia, idiopathic.