Does Calcium Supplementation Reduce the Risk of Urinary Oxalate Calculi after Jejunoileal Bypass for Morbid Obesity?

Twelve patients having received an end-to-side jejunoileal bypass operation for morbid obesity 6-10 years previously were studied over three periods of 2 weeks each. The first period was used for baseline observations without any treatment. For the second period patients were randomly assigned to equimolar (75 mmol/day) oral calcium supplements administered either as a slow release or as a bolus calcium preparation. During the third period these treatments were crossed over. The calcium preparations used caused equal reductions in frequency of bowel movements. Both preparations increased serum calcium and serum phosphate, but significance (p < 0.05) was reached only during supplementation with the slow-release preparation. Despite the Intended raising of serum calcium levels, none of the preparations influenced the 24-hour urine oxalate to creatinine ratio or the urine stone index. There are several other reasons for supplying extra calcium after intestinal bypass procedures, but our data do not support the concept of preventing renal stone formation by means of calcium supplementation.