Does level of ligation influence results in a murine biliary obstruction model?

Background: Despite advances in perioperative management, patients with extrahepatic biliary obstruction still experience a high rate of complications and death after surgery. The rat is commonly used as an experimental animal for research in obstructive jaundice. Ligation of the rat bile duct high in the liver hilum is assumed to produce a more severe model of biliary obstruction than low ligation. The differences are attributed to the ability of the rat bile duct to dilate. Differences in level of ligation may, thus, explain some discrepancies between studies. Materials and Methods: To test this hypothesis, female Lewis rats underwent high ligation (HL), low ligation (LL), and sham celiotomy. Colloidal carbon clearance, bilirubin, total serum bile acids, and hematocrit were measured 12 days later. Liver and spleen weight, presence or absence of ascites, infection, and adequacy of ligation were noted and the liver was processed for routine histology and electron microscopy. Results: Although bilirubin levels were higher after HL than after LL, liver and spleen weight, total serum bile salts, and phagocytic constants K and α were not different between these two groups. Gross, histologic, and ultrastructural appearance did not differ between HL and LL groups. Conclusion: High ligation causes greater hyperbilirubinemia than low ligation, but does not alter other parameters including phagocytic constants. The present study does not confirm the hypothesis that HL creates a more severe model than LL; therefore, it is unlikely that differences in level of ligation explain variability in results between studies.