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Recurrent calcium oxalate nephrolithiasis with hypocitraturia and chronic kidney disease — MSRA MCQ

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HardNephrolithiasisRecurrent calcium oxalate nephrolithiasis with hypocitraturia and chronic kidney diseaseMSRA

A 58-year-old man is reviewed in general practice after his fourth calcium oxalate stone in 6 years. Analysis of two passed stones showed more than 80% calcium oxalate. He drinks 2.5 to 3 litres of water daily, avoids carbonated drinks, maintains normal dietary calcium intake and has reduced salt intake to less than 6 g/day. Specialist metabolic assessment shows hypocitraturia, with normal urinary calcium and uric acid excretion. He has no urinary infection or urinary tract obstruction. His eGFR is 43 mL/min/1.73 m², serum potassium is 4.8 mmol/L, and he takes ramipril for albuminuric chronic kidney disease. What is the most appropriate next management plan to reduce stone recurrence?

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Correct answer: E — Withhold pharmacological prophylaxis and seek specialist stone review while continuing current preventive measures.

NICE recommends considering potassium citrate for adults with recurrent stones that are predominantly calcium oxalate, so the recurrent calcium oxalate composition and hypocitraturia initially make this an attractive option. However, the current UK SmPC for potassium citrate contraindicates its use when GFR is 44 mL/min/1.73 m² or less. This patient’s eGFR is 43 mL/min/1.73 m²; ramipril also increases the potential for potassium retention. Monitoring does not override a formal contraindication. Pharmacological prophylaxis should therefore not be initiated in primary care without specialist reassessment. A thiazide is not indicated because NICE limits this option to recurrent predominantly calcium oxalate stones with hypercalciuria after dietary sodium restriction; his urinary calcium is normal. Sodium bicarbonate is not a NICE-recommended substitute for potassium citrate in this setting and adds sodium despite appropriate salt restriction. Allopurinol is not indicated because hyperuricosuria has not been identified. His established high fluid intake, salt restriction and normal calcium intake should continue while specialist review considers an individualised strategy.

Reference: NICE NG118: Renal and ureteric stones: assessment and management — Preventing recurrence (2019; NICE page current in 2026) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations Renodyra 1080 mg modified-release tablets — Summary of Product Characteristics (Revised 17 December 2025) — https://www.medicines.org.uk/emc/product/101807/smpc