A STUDY ON BILIARY DUCTAL SYSTEM AND BILE FISTULA IN THE AMERICAN ALLIGATOR, ALLIGATOR-MISSISSIPPIENSIS

The anomalous arrangement of bile ducts in the Crocodylia has not been fully appreciated. A clear understanding of biliary anatomy is necess ary in order to create complete bile drainage in these reptiles. The o bject of this study was to clarify the anatomy of the bile ductal syst em and to establish total bile fistulas in the American alligator, All igator mississippiensis. Bile duct anatomy was studied in 104 juvenile alligators, and bile fistulas were constructed in seven alligators. I n 93 out of 104 (89%) of the juveniles dissected there was an intercon nection between the right and left hepatic duct before the right hepat ic duct emptied into the gallbladder. The left hepatic duct then enter ed the duodenum independently of the cystic duct which drained the gal lbladder directly into the duodenum. In 8% of the animals, the left he patic duct did not enter the duodenum but joined with the right duct, forming a common hepatic duct that emptied into the gallbladder. In 3% of the cases, the right hepatic duct emptied into the gallbladder, wh ile the left duct had no communication with the right hepatic duct and drained separately into the duodenum. This arrangement of bile ducts is similar to that seen in birds and reflects the common ancestry of c rocodiles and birds. In other reptiles, the biliary system shows much more variability and is different from the alligator. In five of seven alligators In which total biliary diversion was attempted, the biliar y catheter remained in place and stayed patent from 2-7 weeks. Bile fl ow was extremely low (1.5-2.5 ml/24 h) when compared to that of mammal s (80-100 ml/24 h). This study demonstrates the variable nature of the biliary ductal system in Alligator mississippiensis and suggest a met hod for constructing an effective total bile fistula in these animals. (C) 1997 Wiley-Liss, Inc.