Which test best differentiates central DI from nephrogenic DI?

Which test best differentiates central DI from nephrogenic DI?

• A. Water deprivation test only
• B. Desmopressin stimulation test
• C. Serum aldosterone measurement
• D. Urine ketone testing

Answer: (B)

Desmopressin stimulation distinguishes central from nephrogenic diabetes insipidus by testing the kidney’s ability to respond to ADH. Desmopressin is a synthetic ADH analog that acts on the V2 receptors in the collecting ducts to promote water reabsorption. In central DI, where ADH deficiency is the problem, this gives a strong response: urine becomes more concentrated and urine output decreases after administering desmopressin. In nephrogenic DI, the kidneys don’t respond to ADH, so desmopressin produces little or no change in urine osmolality or volume. Because of this direct contrast in renal response, the desmopressin stimulation test is the best way to tell central from nephrogenic DI. Note that a water deprivation test helps distinguish DI from primary polydipsia, but it does not differentiate the two forms of DI on its own.

Desmopressin stimulation distinguishes central from nephrogenic diabetes insipidus by testing the kidney’s ability to respond to ADH. Desmopressin is a synthetic ADH analog that acts on the V2 receptors in the collecting ducts to promote water reabsorption. In central DI, where ADH deficiency is the problem, this gives a strong response: urine becomes more concentrated and urine output decreases after administering desmopressin. In nephrogenic DI, the kidneys don’t respond to ADH, so desmopressin produces little or no change in urine osmolality or volume. Because of this direct contrast in renal response, the desmopressin stimulation test is the best way to tell central from nephrogenic DI. Note that a water deprivation test helps distinguish DI from primary polydipsia, but it does not differentiate the two forms of DI on its own.