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Distal RTA — RACP Paediatrics MCQ

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ModerateNephrologyDistal RTARACP Paediatrics

A 12-month-old presents with failure to thrive, vomiting, and polyuria. Blood gas shows a normal anion gap metabolic acidosis. Urine pH is persistently >5.5 despite systemic acidosis. Renal ultrasound shows bilateral nephrocalcinosis. What is the most likely diagnosis?

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Correct answer: E — Type 1 (distal) RTA

Normal anion gap metabolic acidosis with inappropriately alkaline urine (pH >5.5) and nephrocalcinosis is characteristic of type 1 (distal) RTA. The distal tubule fails to secrete hydrogen ions. Causes include genetic (autosomal dominant/recessive), autoimmune, or drug-induced. Treatment is oral bicarbonate supplementation. Growth improves with correction of acidosis.

Reference: RCH Melbourne – 2023 – RTA CPG; RACP Paediatric Curriculum – Nephrology