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Nephrogenic DI — RACP Paediatrics MCQ

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ModerateNephrologyNephrogenic DIRACP Paediatrics

A 7-year-old presents with polyuria, polydipsia, and nocturia. Serum sodium is 150 mmol/L, serum osmolality is 310 mOsm/kg, and urine osmolality is 150 mOsm/kg. Desmopressin does NOT concentrate the urine. Where is the abnormality?

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Correct answer: D — Kidney (nephrogenic diabetes insipidus)

Nephrogenic DI: kidneys are unresponsive to ADH. Desmopressin fails to concentrate urine (unlike central DI where it does). Causes include X-linked (AVPR2 mutation), autosomal recessive (AQP2), or acquired (lithium, hypercalcaemia, renal disease). Treatment includes adequate hydration, thiazide diuretics, and NSAIDs.

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