Pathophysiology Underlying Manifestation of Pancreaticobiliary Maljunction Throughout Life.

Pancreaticobiliary maljunction (PBM) is an anomaly in which the bile and pancreatic ducts join outside the area of action of the sphincter. PBM is typically accompanied by choledochal cysts (dilated PBM); however, cases of PBM without biliary dilatation (nondilated PBM) have also been reported. PBM manifests throughout life. The presentation remains unclear due to age-dependent differences in its pathophysiology. PBM symptoms may be attributed to biliary obstruction caused by substances that differ with age: calcium bilirubinate debris in neonates, protein plugs in children, and gallstones in adults. Each substance is associated with PBM types. Debris occurs in dilated PBM with a narrow segment. Plugs are produced by pancreatobiliary reflux in dilated PBM but rarely in nondilated PBM. Bile duct gallstones have been implicated in dilated PBM with a narrow segment, while gallbladder gallstones may be coincident. Pancreatobiliary reflux appears to induce carcinogenesis silently and cause symptoms in the elderly. A large number of adults with PBM are reported to be asymptomatic. In summary, PBM on its own appears to cause no symptoms. However, associated biliary stricture and pancreatobiliary regurgitation produce obstructive substances or cancers, which may lead to symptoms. The substances may vary with the patient's age and PBM types.