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Renal Tubular Acidosis — RACP Adult Medicine MCQ

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HardNephrologyRenal Tubular AcidosisRACP Adult Medicine

A 50-year-old woman with Sjögren syndrome presents with progressive renal impairment. Serum creatinine is 180 µmol/L. Urinalysis shows sterile pyuria with a urine pH of 7.0. ABG shows pH 7.30, HCO₃ 15 mmol/L, and serum potassium is 2.8 mmol/L. What is the most likely renal complication?

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Correct answer: A — Distal (type 1) renal tubular acidosis

Sjögren syndrome is a classic cause of distal (type 1) RTA due to autoimmune-mediated tubulointerstitial nephritis affecting the collecting duct. Features include non-anion-gap metabolic acidosis, alkaline urine (pH >5.5 despite acidosis), hypokalaemia, and nephrocalcinosis/nephrolithiasis. Type 4 RTA causes hyperkalaemia. Treatment includes oral sodium bicarbonate and potassium supplementation.

Reference: eTG – 2025 – Nephrology; EULAR – 2020 – Sjögren Syndrome Guidelines