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Distal renal tubular acidosis — RACP Adult Medicine MCQ

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HardNephrologyDistal renal tubular acidosisRACP Adult Medicine

A 29-year-old woman with Sjögren syndrome has recurrent renal stones and muscle weakness. Bicarbonate is 16 mmol/L, chloride is elevated, anion gap is normal and urine pH is 6.5 despite metabolic acidosis. Potassium is 3.0 mmol/L. What is the most likely diagnosis?

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Correct answer: E — Distal renal tubular acidosis

Non-anion-gap metabolic acidosis with inappropriately alkaline urine, hypokalaemia and stones suggests distal RTA, which is associated with Sjögren syndrome. DKA and lactic acidosis produce high anion gap acidosis. Proximal RTA is less associated with alkaline urine during established acidosis, and respiratory alkalosis is a primary respiratory disorder.

Reference: Kidney Health Australia/CARI Guidelines; AMH