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Recurrent calcium oxalate nephrolithiasis with hypocitraturia — MSRA MCQ

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ModerateNephrolithiasisRecurrent calcium oxalate nephrolithiasis with hypocitraturiaMSRA

A 61-year-old man is reviewed in general practice after passing his third stone in 5 years. Stone analysis on two occasions has shown calcium oxalate composition of more than 80%. He drinks 2.5 to 3 litres of water daily, has reduced his salt intake to less than 6 g/day and maintains a normal dietary calcium intake. Specialist metabolic assessment shows hypocitraturia, no hypercalciuria and no hyperuricosuria. His eGFR is stable at 52 mL/min/1.73 m² and serum potassium is 4.5 mmol/L. He has no urinary infection and takes amlodipine only. Which is the most appropriate additional pharmacological management plan to reduce stone recurrence?

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Correct answer: B — Start potassium citrate and monitor serum potassium and renal function

This patient has recurrent predominantly calcium oxalate stones despite appropriate fluid, salt and calcium advice. NICE recommends considering potassium citrate for adults with recurrent stones that are predominantly calcium oxalate; this recommendation does not require documented hypocitraturia, although his hypocitraturia provides an additional mechanistic rationale. His eGFR of 52 mL/min/1.73 m² does not preclude use of the licensed modified-release potassium citrate preparation, but it requires monitoring of renal function and serum potassium because reduced potassium excretion increases the risk of hyperkalaemia. A thiazide is not the best option because NICE limits consideration of thiazides to recurrent predominantly calcium oxalate stones with hypercalciuria after sodium restriction; he does not have hypercalciuria. Allopurinol would be appropriate for a relevant urate abnormality, not isolated hypocitraturia with calcium oxalate stones. An eGFR above 60 mL/min/1.73 m² is not required: the relevant SmPC threshold is contraindication at GFR 44 mL/min/1.73 m² or below, with monitoring advised at GFR 45–59 mL/min/1.73 m². Dietary measures should continue, but recurrence despite adherence supports adding pharmacological prevention.

Reference: Renal and ureteric stones: assessment and management (NG118) — Recommendations (Published January 2019; updated May 2026) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations Renodyra 1080 mg modified-release tablets — Summary of Product Characteristics (2026) — https://www.medicines.org.uk/emc/product/101807/smpc Renal and ureteric stones: assessment and management (NG118) — Update information (May 2026) — https://www.nice.org.uk/guidance/ng118/chapter/update-information