Relationship of Bile Acid Pool Size to Biliary Lipid Excretion and the Formation of Litho Genic Bile in Man

Abstract

This study was designed to provide additional information on the relationship between a diminished bile acid pool and cholesterol gallstone formation in man. The total bile acid pool and biliary lipid composition were determined in 10 patients with gallstones and 10 patients without gallstones. Bile was obtained from all patients at the same time of day (8 am to 9 am fasting). From these data the amounts of biliary phospholipid and cholesterol secreted during a single total bile acid pool cycle were calculated. In agreement with our earlier findings, patients with cholesterol gallstones (and a lithogenic bile) were found to have a greatly diminished bile acid pool. The bile acid pool was 50% smaller than in patients without gallstones (and a normal bile). Patients with gallstones also had a greatly decreased phospholipid excretion. There was a slight decrease in the excretion of biliary cholesterol in patients with gallstones, but this difference was not significant. There was a high degree of correlation (r = 0.80) between phospholipid excretion and bile acid pool size. There was a lesser degree of correlation (r = 0.61) between bile acid pool size and cholesterol excretion. Phospholipid excretion was considerably more responsive to bile acid pool size than cholesterol. The results of this study suggest that patients with cholesterol .gallstones have a diminished bile acid pool and, as a consequence, a decreased phospholipid excretion and only a slight decrease in cholesterol excretion. This leads to a relative decrease in bile salts and phospholipid in relation to cholesterol and a bile saturated with cholesterol. The breakpoint in bile acid pool size between male patients with and without gallstones was estimated to be in the vicinity of 1.6 to 1.8 g.