skip to main content

Post-Surgical Central DI — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

ModerateEndocrinologyPost-Surgical Central DIRACP Adult Medicine

A 40-year-old woman post-pituitary surgery for craniopharyngioma develops polyuria (8 L/day) on day 1 post-op. Na⁺ is 150 mmol/L. Serum osmolality 310 mOsm/kg. Urine osmolality 100 mOsm/kg (dilute). After DDAVP 2 μg IV, urine osmolality rises to 700 mOsm/kg. What is the most likely diagnosis?

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

Reveal the answer and explanation

Correct answer: C — Central diabetes insipidus

Post-pituitary surgery polyuria with hypernatraemia, dilute urine (inappropriately low for serum hypertonicity), and response to DDAVP (urine concentrates) is central DI. ADH deficiency from surgical damage to posterior pituitary/stalk. May follow a triphasic pattern: DI (days 1-5) → transient SIADH (days 5-10, from uncontrolled ADH release from damaged neurons) → permanent DI. DDAVP replacement is required.

Reference: eTG Endocrine – 2024 – Post-Surgical DI; Endocrine Society 2023