The effect of jejunoileal bypass on bile composition and the formation of billiary calculi

In our series of 101 patients with small bowel bypass for morbid obesity, nine developed biliary calculi postoperatively during a mean follow-up of 29.6 months. The development of gallstones depends in part on biliary cholesterol saturation and on the zeta potential of bile. In eight consecutive patients, the lithogenicity of bile was assessed by the methods of Small, Swell and Isaksson, which are dependent on cholesterol saturation. Postoperatively, the lithogenic score decreased in six and increased in two patients, one of which developed gallstones. Taurine bile salt conjugation tends to prevent aggregation of micelles by increasing the zeta potential. The biliary glycine/taurine ratio increased (p less than 0.05) from 4.6 to 5.9 postoperatively. These results suggest that the increased incidence of cholelithiasis following small bowel bypass is not only due to a relative change in bile composition but is probably more significantly due to an increase in the biliary glycine/taurine ratio and a consequent decrease in the biliary zeta potential.