Regarding the etiology of congenital choledochal cysts, since 1969, when Babitt first proposed the concept of “abnormal pancreaticobiliary ductal conjunction” by means of cholangiopancreatography, the majority of scholars have agreed with this theory through empirical summarization. That is to say, anatomically, the bile duct and pancreatic duct converge early outside the duodenal wall, and the common channel is too long for the Oddi’s sphincter of the duodenal papilla to effectively control the merging, so that bile and pancreatic juice converge prematurely to produce biliopancreatic reflux. Some rare diverticular and prolapsed congenital choledochal cysts may be caused by other factors, such as abnormal development of the primitive bile ducts, proliferation of a certain segment and over-vacuolization of a certain segment during the process of embryonic vacuolization; abnormal development of the biliary nerves, and the reduction and lack of ganglion cells on the wall of the choledochal ducts.