How great is the incidence of truly congenital common bile duct dilatation?

In an attempt to investigate the causes of common bile duct dilatation (CBDD), activity of the pancreatic enzymes in bile aspirated from the dilated duct during laparotomy was measured in 24 children with CBDD. The reasoning behind this is the fact that the existence of activated pancreatic enzymes, namely raised activity of all enzymes accompanied by trypsin activation, can be regarded as an acquired result of an anomalous choledochopancreaticoductal junction (ACP-DJ). All of the pancreatic enzymes measured were activated in 14 cases (58.3%) but no evidence of activation of enzymes, such as trypsin or others except for amylase and lipase, was observed in the remaining 10 cases (41.7%), whether an ACPDJ was present or absent. Eight of the 10 patients with no enzyme activation (33.3% of the total) were less than 2 months old. The findings in these eight infants, which included cystic dilation or hypoplasia of the intrahepatic duct, provide strong suggestive evidence of the congenital nature of these cases. These results suggest that at least one third of CBDD cases are congenital and the remaining cases are either acquired or a combination of congenital and acquired, or both.