Experimental detachment of the canine bile duct to evaluate mechanisms of the dilated bile duct.

The factors inducing biliary dilatation were studied morphologically and functionally by cholangiography and cholangiomanometry in experimental models of chronic biliary dilatation. These models were produced by four methods: Constriction of the lower bile duct (Group 1), formalin infusion into the duodenal papilla (Group 2), detachment of the extrahepatic bile duct (Group 3), and sphincterotomy (Group 4). Biliary dilatation was observed in the first three groups but not in the fourth group. An increase in the intraductal pressure due to blockage of the biliary outflow tract was considered to be the cause of biliary dilatation in Group 1 and 2. In Group 3, the function of the lower bile duct, including the papilla was intact, and reduced resistance of the bile duct wall and due to the loss of the support from the surrounding connective tissue was considered to have induced biliary dilatation. These results suggest that experimental chronic biliary dilatation can be produced by two approaches: 1) Blockage of bile flow in the papilla or the bile duct, and 2) detachment of the bile duct without disturbing bile flow.