A hydrophilic bile acid effects partial dissolution of cholesterol gallstones in the prairie dog

Gallstone formation and dissolution were studied in a prairie dog model of cholesterol (CH) cholelithiasis. Gallstones were induced in 49 prairie dogs by feeding 1.2% CH in a nutritionally adequate semisynthetic diet for 6 wk (period 1). At 6 wk, gallstones had developed in all animals examined. The diets were modified by reducing the amounts of CH to 0.4, 0.2, 0.1 and 0.0% (diets 1-4); hyodeoxycholic acid (HDA; 30 mg/kg/day) was added to these diets (diets 5-8). All animals were fed the modified experimental diets for an additional 8 wk (period 2). At week 14, spontaneous gallstone dissolution had not occurred, even in the groups given no added dietary CH during period 2 (group 4). Addition of HDA to the diet tended to reduce the incidence of biliary CH crystals and the size and number of CH gallstones. Biliary CH remained elevated and the lithogenic indices in all groups were found to be greater than 1.0 at the end of the experiment. Liver and plasma CH levels tended to be lower in the groups fed HDA. In these groups, HDA and 6 beta HDA became the major biliary bile acids. This study demonstrates that HDA achieved partial dissolution of gallstones in bile supersaturated with CH.