In nephrogenic diabetes insipidus, DDAVP administration results in which outcome?

In nephrogenic diabetes insipidus, DDAVP administration results in which outcome?

• A. No concentration of urine
• B. Hyponatremia
• C. Normal concentration with increased urine osmolality
• D. Rapid dehydration correction

Answer: (A)

Nephrogenic diabetes insipidus means the kidney’s collecting ducts don’t respond to vasopressin, so water reabsorption cannot be increased. Desmopressin (DDAVP) acts like vasopressin, but in this condition the renal receptors or aquaporin channels are defective, so the tubules fail to concentrate urine even after DDAVP. The result is persistently dilute, high-volume urine with little to no rise in urine osmolality. This explains why the correct outcome is that urine concentration does not increase after DDAVP, and the patient remains susceptible to dehydration and hypernatremia if fluids aren’t adequately replaced. Hyponatremia is unlikely because DI features water loss, not retention; central DI would show increased urine osmolality after DDAVP, not nephrogenic; rapid dehydration correction is not an expected immediate effect since DDAVP does not enhance water reabsorption in the kidneys here.

Nephrogenic diabetes insipidus means the kidney’s collecting ducts don’t respond to vasopressin, so water reabsorption cannot be increased. Desmopressin (DDAVP) acts like vasopressin, but in this condition the renal receptors or aquaporin channels are defective, so the tubules fail to concentrate urine even after DDAVP. The result is persistently dilute, high-volume urine with little to no rise in urine osmolality. This explains why the correct outcome is that urine concentration does not increase after DDAVP, and the patient remains susceptible to dehydration and hypernatremia if fluids aren’t adequately replaced. Hyponatremia is unlikely because DI features water loss, not retention; central DI would show increased urine osmolality after DDAVP, not nephrogenic; rapid dehydration correction is not an expected immediate effect since DDAVP does not enhance water reabsorption in the kidneys here.