[Mechanism of the bile duct dilatation in congenital dilatation of the common bile duct].

Radiographic studies including operative cholangiography, endoscopic retrograde cholangiopancreaticography and percutaneous transhepatic cholangiography were performed in 44 patients with congenital dilatation of the common bile duct. The relation between the maximum transverse diameter of the common bile duct (CBD) as an indicator of the degree of dilatation and various possible factors causing dilatation of CBD was studied. Among these factors, the length of the narrow segment (X) was closely related with the maximum transverse diameter (Y). The relation of these two was expressed by a simple equation; log Y = 0.068X + 1.06 (r = 0.934, p less than 0.001, n = 19) Dilatation of CBD has been successfully produced by narrowing the ductal lumen with a small plastic tube encirculating the distal common bile duct in dogs. Experimental dilatation was quite similar with congenital dilatation. In addition, the relation between the maximum transverse diameter (Y') and the length of the narrow segment (X') was also expressed in the following simple equation; log Y' = 0.060X' + 0.88 (r = 0.972, p less than 0.001, n = 18) The present studies did not support the hypothesis that abnormal junction of the pancreatico-biliary system might be the primary cause of congenital dilatation of CBD. They suggest that the stenosis of the distal CBD in the fetal life may determine dilatation of CBD.