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Post-infectious lactose intolerance — RACP Paediatrics MCQ

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ModerateGIPost-infectious lactose intoleranceRACP Paediatrics

An 18-month-old develops watery diarrhoea, abdominal cramping, and bloating 2 weeks after a rotavirus gastroenteritis. Stool reducing substances are positive. Symptoms resolve when lactose is removed from the diet and recur on reintroduction. What is the most likely diagnosis?

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Correct answer: D — Post-infectious lactose intolerance

Post-infectious (secondary) lactose intolerance is common after viral gastroenteritis, particularly rotavirus. Brush border lactase is damaged by the infection and may take 2-6 weeks to recover. Temporary lactose-free diet with gradual reintroduction is appropriate. It is self-limiting.

Reference: RCH Melbourne – 2023 – Chronic Diarrhoea CPG; RACP Paediatric Curriculum – GI