The mucosal lining of the intramural common bile duct as a determinant of ductal opening pressure.

Microanatomical evidence is presented which shows that the lumen of the intraduodenal portion of the common bile duct is almost completely filled by folds of a highly vascularized mucosa in the dog, cat, rabbit, and human. These folds are most apparent near the intraduodenal ductal orifice, where they almost completely occlude the lumen. Physiological data are presented which indicate that changes in systemic arterial blood pressure are associated with changes in the opening pressures of the choledochoduodenal junction of the cat and dog, which vary in the same direction. Experimental results indicate that bile duct opening pressures of these two species are increased by the intraductal administration of histamine and reduced by the intraductal administration of norepinephrine. A histological examination of the intraductal mucosal folds in this area, subsequent to the administration of the elevating agent, revealed a marked presence of vascular engorgement. It is concluded that the most significant determinant of changes in ductal opening pressures in the cat and dog is probably the state of the mucosal vasculature of the terminal portion of the common bile duct.