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Central DI Diagnosis — RACP Paediatrics MCQ

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ModerateEndocrinologyCentral DI DiagnosisRACP Paediatrics

A 6-year-old boy has polyuria, polydipsia, and is found to have a urine osmolality of 100 mOsm/kg despite being dehydrated (serum osmolality 310 mOsm/kg). Administration of desmopressin results in a concentrated urine (800 mOsm/kg). Where is the abnormality?

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Correct answer: B — Posterior pituitary (central DI)

Central diabetes insipidus: inadequate ADH secretion from the posterior pituitary. Desmopressin responsiveness confirms central (rather than nephrogenic) DI. Causes include craniopharyngioma, Langerhans cell histiocytosis, post-neurosurgery, and idiopathic. MRI pituitary shows absent posterior pituitary bright spot.

Reference: RCH Melbourne – 2024 – Clinical Practice Guidelines: Diabetes Insipidus