A patient with excessive thirst and polyuria has a urine osmolality that does not increase after desmopressin administration. What is the most likely diagnosis?

✓ Correct Answer: Option B

Nephrogenic diabetes insipidus is characterized by kidney tubules that do not respond to ADH. Since desmopressin is an ADH analog, failure to concentrate urine after its administration indicates a renal resistance, rather than a deficiency of ADH (central DI).