Diabetes Insipidus

A 55-year-old man with a non-functioning pituitary adenoma undergoes transsphenoidal surgery. On postoperative day 3, he develops polyuria (8 L/day), polydipsia, and serum sodium of 148 mEq/L. What is the most likely diagnosis?

A 32-year-old man from Delhi presents to the emergency department with severe polyuria (8–10 L/day) and polydipsia for 3 days. He has a history of head trauma 2 weeks ago following a motor vehicle accident. Vital signs: BP 110/70 mmHg, HR 98/min, temperature 37.2°C. Serum sodium 148 mEq/L, serum osmolality 310 mOsm/kg, urine osmolality 85 mOsm/kg. A desmopressin (DDAVP) challenge test is performed, and urine osmolality rises to 580 mOsm/kg within 2 hours. What is the most likely diagnosis?

A 28-year-old woman from Bangalore presents with a 6-month history of progressive polyuria (7–8 L/day), polydipsia, and nocturia (8–10 times per night). She denies recent head trauma or surgery. Physical examination is unremarkable. Laboratory findings: serum sodium 146 mEq/L, serum osmolality 305 mOsm/kg, urine osmolality 92 mOsm/kg. A water deprivation test is performed: after 8 hours of fluid restriction, urine osmolality remains 110 mOsm/kg and serum sodium rises to 152 mEq/L. Following DDAVP administration (10 μg intranasally), urine osmolality increases to 620 mOsm/kg. MRI brain with pituitary protocol is normal. What is the most likely diagnosis?

A 28-year-old man presents to the emergency department with severe polyuria (8 L/day) and polydipsia for 3 days. He has no prior medical history. Vital signs: BP 100/65 mmHg, HR 102/min. Serum sodium 148 mEq/L, osmolality 310 mOsm/kg. Urine osmolality 95 mOsm/kg. A non-contrast CT head performed for headache shows a sellar mass. After fluid resuscitation, desmopressin 10 µg intranasally is given, and urine output drops to 2 L/day with urine osmolality rising to 280 mOsm/kg. What is the most likely diagnosis?

A 28-year-old man presents to the emergency department with a 3-day history of severe polyuria (8–10 L/day) and polydipsia. He reports a recent head injury from a motor vehicle accident 1 week ago, treated conservatively. On examination, he is alert but appears dehydrated; BP 100/62 mmHg, HR 110/min. Serum sodium is 148 mEq/L, serum osmolality 310 mOsm/kg. Urine osmolality is 120 mOsm/kg. A water deprivation test is performed: after 8 hours of fluid restriction, urine osmolality remains 130 mOsm/kg. He is then given desmopressin 10 µg intramuscularly; 2 hours later, urine osmolality rises to 580 mOsm/kg. What is the most likely diagnosis?