Nephrology Question 75

A 28-year-old man is evaluated for recurrent nephrolithiasis. Medical history is significant for Crohn disease complicated by multiple small bowel strictures requiring resection. He began developing kidney stones 3 years ago following his last bowel surgery. Analysis of the stones has consistently shown calcium oxalate, and he has been adherent to a low oxalate diet, oral hydration to maintain urine output of at least 2 L/d, and intake of 2 g of calcium carbonate with each meal. However, he has continued to have periodic episodes of kidney stones. Medical history is otherwise unremarkable. Medications are infliximab and calcium carbonate.

On physical examination, temperature is 37.1 °C (98.8 °F), blood pressure is 131/78 mm Hg, pulse rate is 84/min, and respiration rate is 12/min. BMI is 22. The abdominal examination shows healed surgical incisions and is otherwise unremarkable. The remainder of the examination is normal.

Laboratory studies, including complete blood count, electrolytes, and kidney function, are normal. Urinalysis is normal; 24-hour urine chemical analysis shows normal levels of calcium, citrate, and uric acid, but elevated oxalate.

Plain abdominal radiographs show multiple small stones in both kidneys.

Which of the following is the most appropriate additional treatment for this patient?

A  Cholestyramine

B  Hydrochlorothiazide

C  Potassium citrate

D  Pyridoxine

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