Water test

The water ban test means that after a certain period of time (usually 1-2 weeks), the water is banned completely the night before the test. Those who cannot tolerate the overnight water ban can start water ban at 4 am. Normal people with increased blood osmotic pressure after water deprivation reduce circulating blood volume, both stimulate AVP release, reduce urine output, increase urine specific gravity, increase urine osmotic pressure, and small changes in blood osmotic pressure. The clinical observation of the water-free test started at 8 am. Observing body weight, heart rate, blood pressure, urine volume, urine specific gravity, urine and osmotic pressure, patients with complete pituitary diabetes insipidus have no decrease in urine volume and specific gravity after water withdrawal If it does not rise, the urine osmotic pressure is not high, or even lower than the blood osmotic pressure level, and weight loss occurs. If the weight loss is greater than 3%, the test should be stopped immediately. Patients with partial pituitary diabetes insipidus may have a partial decrease in urine output during the test. The urine specific gravity or osmotic pressure may increase to a certain extent, but it may not reach the normal level. Renal diabetes insipidus did not change much in urine volume, urine specific gravity and urine osmotic pressure during the test.