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Distal RTA Type 1 — FRCA Primary MCQ

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HardPhysiology - RenalDistal RTA Type 1FRCA Primary

Which finding best characterises distal (type 1) renal tubular acidosis?

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Correct answer: DImpaired distal hydrogen-ion secretion with metabolic acidosis and inappropriately high urine pH

The best answer is “Impaired distal hydrogen-ion secretion with metabolic acidosis and inappropriately high urine pH”. Type 1 RTA reflects failure of distal acid secretion, typically producing normal-anion-gap metabolic acidosis with urine pH that remains inappropriately high. Hypokalaemia and nephrolithiasis are common associations. Type 2 RTA is a proximal bicarbonate-reabsorption defect, whereas type 4 RTA is linked to hypoaldosteronism or aldosterone resistance and hyperkalaemia.

Reference: Royal College of Anaesthetists, Primary FRCA Syllabus 2021: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf