Gallbladder filling and post-ceruletide emptying in prairie dogs and rabbits

The filling and emptying characteristics of the gallbladder in prairie dogs and rabbits were studied to assess the importance of the residual bile in the pathogenesis of gallstones. In prairie dogs under ketamine/xylazine anesthesia, a significantly larger fraction (p = 0.001) of hepatic bile entered the gallbladder (87 +/- 8%) than the intestine during fasting and very little bile emptied (0-3% ejection fraction) following ceruletide infusion. In rabbits under similar anesthesia, only a small fraction of hepatic bile entered the gallbladder (4 +/- 2%) during fasting, and the gallbladder emptied almost completely (85% ejection fraction) following ceruletide infusion. The resultant higher residual bile in the prairie dog gallbladder and lower residual bile in the rabbit gallbladder may explain why gallstones form so readily in prairie dogs but not in rabbits when fed a lithogenic diet. These similarities and differences in gallbladder function must be taken into account when considering any animal as a model for gallstone formation.