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Enteric hyperoxaluria nephrolithiasis — ABIM Board MCQ

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HardNephrologyEnteric hyperoxaluria nephrolithiasisABIM Board

A 54-year-old man with Crohn disease and prior ileal resection has recurrent calcium oxalate stones. Urine volume is 1.3 L/day, urinary oxalate is markedly elevated, and urinary calcium is normal. Which prevention plan best targets his stone mechanism?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: D — Use calcium with meals plus fluid and dietary oxalate restriction

The best answer is “Use calcium with meals plus fluid and dietary oxalate restriction”. Fat malabsorption leaves luminal calcium bound to fatty acids, increasing free oxalate absorption. Calcium taken with meals binds that oxalate in the gut; low calcium intake can therefore worsen enteric hyperoxaluria. Higher urine volume and targeted oxalate restriction also reduce supersaturation. Allopurinol is not directed at this abnormality, and urine acidification does not correct intestinal oxalate loading.

Reference: AUA Medical Management of Kidney Stones Guideline: https://www.auanet.org/documents/Guidelines/PDF/clinical-guidance/Medical-Management-of-Kidney-Stones.pdf