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Central diabetes insipidus — SCE Endocrinology MCQ

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ModeratePituitaryCentral diabetes insipidusSCE Endocrinology

A 46-year-old man is 2 days post-trans-sphenoidal surgery for a non-functioning pituitary macroadenoma. Urine output is 350 ml/hour, sodium is 151 mmol/L and paired osmolality shows serum 309 mOsm/kg with urine 110 mOsm/kg. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Central diabetes insipidus

Central diabetes insipidus is best because post-pituitary surgery hypernatraemia with high-volume dilute urine indicates central diabetes insipidus. The alternatives are less appropriate because SIADH and cerebral salt wasting cause hyponatraemia; osmotic diuresis has high urine osmolality; primary polydipsia usually lowers sodium. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: Society for Endocrinology diabetes insipidus guidance