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Recurrent calcium oxalate nephrolithiasis with hypercalciuria — MSRA MCQ

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HardNephrolithiasisRecurrent calcium oxalate nephrolithiasis with hypercalciuriaMSRA

A 59-year-old woman is reviewed after passing her fourth symptomatic ureteric stone in 4 years. Analysis of two retrieved stones showed 80% calcium oxalate. Serum adjusted calcium is normal. A 24-hour urine collection shows hypercalciuria; urinary citrate and urate are normal. Her eGFR is stable at 42 mL/min/1.73 m² and serum potassium is 4.4 mmol/L. She has no active urinary infection or obstruction. She now drinks 2.5–3 litres of water daily, has reduced salt intake to 5 g/day, maintains a normal dietary calcium intake, avoids carbonated drinks and has lost weight. She wishes to reduce further stone recurrence. Which is the most appropriate pharmacological preventive strategy now?

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Correct answer: A — Start a thiazide, with appropriate electrolyte and renal-function monitoring

This patient has recurrent stones that are predominantly calcium oxalate, documented hypercalciuria, and has already achieved the required dietary sodium restriction. NICE therefore recommends considering a thiazide alongside dietary and lifestyle measures. Biochemical monitoring is appropriate because thiazides can affect renal function and electrolytes. Potassium citrate is otherwise a plausible NICE-supported option for recurrent predominantly calcium oxalate stones, irrespective of urinary citrate in adults. However, the available UK potassium citrate SmPC contraindicates its use where GFR is 44 mL/min/1.73 m² or lower; her eGFR is 42 mL/min/1.73 m². Monitoring does not overcome a contraindication. Allopurinol would be more relevant to uric acid stone disease or a demonstrated urate-driven mechanism, neither of which is present. Calcium restriction or supplementation is not indicated: NICE advises maintaining, rather than restricting, normal dietary calcium intake. Lifestyle measures remain essential, but she has recurrent stones despite adherence and meets NICE criteria for additional thiazide therapy.

Reference: Renal and ureteric stones: assessment and management (NG118) — Recommendations (Published 8 January 2019; last reviewed 26 February 2021) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations Renodyra 1080 mg modified-release tablets — Summary of Product Characteristics (Last updated on emc 9 January 2026) — https://www.medicines.org.uk/emc/product/101807/smpc