The high incidence of anomalous pancreatobiliary duct union (APBDU) in
children who have a choledochal cyst has been well documented. Additi
onally, cylindrical dilatation of the bile duct has been reproduced in
animal models by anastomosing the pancreatic duct to the bile duel. I
n recent years, APBDU has been considered a possible etiologic factor
in the formation of a choledochal cyst. The authors observed a progres
sive cylindrical dilatation of the common bile duct in a 6-year-old bo
y over an 18-month period, An operative cholangiogram showed a type I,
choledochal cyst and a type B APBDU (Todani classification). This cli
nical experience suggests that a normal common bile duct in children c
an be progressively dilated and become an acquired choledochal cyst ar
ising as a complication of the preexisting APBDU.