Etiological relationships between choledochal cyst and anomalous junction of the pancreaticobiliary ductal system

The etiology of choledochal cyst has been investigated by clinicians and pathologists primarily of Germany, Austria, United States, United Kingdom, and Japan from the end of the last century, but Japanese investigators contributed greatly to the study of the relationship between choledochal cyst and anomalous junction of the pancreaticobiliary ductal system. Heid (1893) is considered to be the first to document choledochal cyst associated with anomalous pancreaticobiliary junction, but it was probably Kozumi et al. (1916) that first evaluated anomalous junction in relation to the etiology of choledochal cyst. Yotsuyanagi (1936), who is noted for his work on the etiological studies of choledochal cyst, attached particular importance to anomalous junction and attempted to establish a relationship between dysplasia of the primordial common bile duct and its anomalous junction with the pancreatic duct. It is no exaggeration to say that this area was led by Japanese investigators even after the introduction of Babbitt's anomalous junction theory (1968). In this review, etiological theories of choledochal cyst and their changes with time were discussed separately for those before and after the advent of Babbitt's anomalous junction theory (1968) with particular reference to the causative relationship between anomalous junction and choledochal cyst. Although there is as yet no definite answer to this problem, the theories advanced to date are considered to be summarized as the following three major lines of thought: 1) bile duct dilatation and anomalous junction are both congenital dysplasia occurring simultaneously during the embryonic development, 2) bile duct dilatation is a secondary change induced by influx of pancreatic juice into the biliary tract due to anomalous pancreaticobiliary junction, and 3) bile duct dilatation is induced secondarily by stenosis of the distal bile duct, which is a part of complex anomaly of the pancreaticobility system. Which of these etiological mechanisms is more important than others must still be clarified, but these three factors are considered to be interrelated with one another in the etiology of choledochal cyst.