Enhanced gallbladder absorption during gallstone formation: the roles of cholesterol saturated bile and gallbladder stasis.

Cholesterol saturated bile and gallbladder stasis are important factors in the pathogenesis of cholesterol gallstones. The degree to which either or both of these factors affect gallbladder transport of fluid remains obscure. The authors tested the hypothesis that both cholesterol saturated bile and gallbladder stasis, and not stasis alone, promotes gallbladder fluid absorption. Prairie dogs were maintained for 2 weeks on either a control chow, total parenteral nutrition (TPN), or a 1.2% cholesterol enriched chow. The bile acid pool was labeled with 14C-cholic acid and indexes for cholesterol saturation (CSI) and gallbladder stasis (Rsa) were determined. Fluid transport was indirectly measured by calculating the ratio of gallbladder to hepatic bile concentrations of individual and total biliary lipids. Despite evidence of stasis in prairie dogs maintained on TPN, bile was unsaturated, and gallbladder absorption was not appreciably changed. In contrast, cholesterol-fed animals had cholesterol supersaturated bile, gallbladder stasis, and altered gallbladder absorption, as manifested by a significant change in the ratio of gallbladder to hepatic bile concentrations of individual and total biliary lipids. These data suggest that both cholesterol saturated bile and gallbladder stasis, and not stasis alone, are essential in promoting the enhanced gallbladder absorption, which has previously been observed during early cholesterol gallstone formation.