Experimental study of the pathogenesis of choledochal cyst and pancreatitis, with special reference to the role of bile acids and pancreatic enzymes in the anomalous choledocho-pancreatico ductal junction.

To investigate the mechanisms initiating pancreatic enzyme activation followed by the development of a choledochal cyst and/or pancreatitis under anomalous choledocho-pancreatic ductal junction (ACPDJ), choledocho-pancreatic end-to-side ductal anastomosis was successfully performed in 40 puppies as an experimental model of ACPDJ. As a result, reflux of pancreatic juice into the common bile duct readily and continuously occurred, and all pancreatic enzymes in bile obtained from the common bile duct were activated. Total bile acids increased about 2 months after surgery, and the ratio of taurodeoxycholic acid to total bile acids increased within the first months after surgery. Various degrees of common bile duct dilatation developed in all puppies within 7 to 10 days after the surgery, and no further dilatation occurred in the subsequent period. Histological change in the pancreatic duct was less prominent than that in the common bile duct, but histologically proved chronic pancreatitis was found in three of 23 sacrificed dogs, in which there was strong evidence of free and massive regurgitation of the bile-pancreatic juice mixture between the bile and the pancreatic duct systems. These findings in this experimental study constitute the first step to prove that ACPDJ, which is often found in patients with choledochal cyst, is an important etiologic factor not only for choledochal cyst but also for pancreatitis, and bile acids play an important role in the mechanism of pancreatic enzyme activation under the condition of ACPDJ.