DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS — In addition to nephrogenic and central diabetes insipidus (DI), a
variety of conditions may result in the complaint of polyuria, including psychogenic polydipsia, prostatic hypertrophy, or
osmotic diuresis (including postobstructive diuresis). (See "Clinical manifestations and diagnosis of urinary tract
obstruction and hydronephrosis", section on 'Prognosis and recovery of renal function'.)
The cause of polyuria is often suggested from the history (eg, age of onset and eliciting the possible presence of the
different causes of DI), and rarely by the plasma sodium concentration. Specific testing is then performed to establish the
diagnosis.