Polyuria and polydipsia — viva

Opening (must-hit)

"This is a water diuresis after pituitary surgery — the normal glucose excludes an osmotic diuresis, and the urine osmolality of 120 with a serum osmolality that is clearly raised confirms a water diuresis. Two weeks after craniopharyngioma surgery this is central diabetes insipidus until proven otherwise, complicated now by hypernatraemia at 152. My immediate priority is the sodium: he needs intravascular volume restoration with isotonic saline, then slow free-water correction at no more than 0.5 mmol per litre per hour, max 10 to 12 over 24 hours, to avoid cerebral oedema. Once the sodium is controlled and his cortisol status is confirmed, I would confirm central disease and start desmopressin, recognising that after pituitary surgery the picture can be complicated by the triphasic response." ^[4][12]