Glands of bile duct

The glands of the bile duct (Peribiliary glands; PBGs) are minute tubuloalveolar glands located within and around the walls of the extrahepatic bile ducts, intrahepatic large bile ducts, and cystic duct. They are lined by biliary epithelial cells and connected to the bile duct lumen via small glandular canals.

Anatomical Classification

Peribiliary glands are divided into two types based on their location relative to the duct wall:

• Intramural glands simple tubular glands situated within the bile duct wall that drain directly into the ductal lumen. They are sparsely and irregularly distributed and contain predominantly mucinsecreting cells.

• Extramural glands located in the periductal connective tissue outside the duct wall. They are composed of multiple lobules of seromucinous acini with a conducting system that drains into the ductal lumen via their own conduits. Pancreatic exocrine acini are occasionally admixed with these glands.

Peribiliary glands are most numerous at branch points of the biliary tree, including the cystic duct junction, perihilar region, and periampullary region. They are particularly abundant at the ampulla of Vater.

Functions

• Secretory function PBGs secrete both neutral and acid mucin into the bile duct lumen, contributing to bile modification and mucosal protection. The extramural glands also produce digestive enzymes including alphaamylase, trypsin, and pancreatic lipase.

• Stem/progenitor cell niche PBGs harbor multipotent stem/progenitor cells capable of selfrenewal and differentiation into hepatocytes, cholangiocytes, or pancreatic islet cells, playing a critical role in biliary epithelial turnover and regeneration.

• Immune function Specific and nonspecific immune responses within the glandular system may contribute to maintaining the sterility of bile.

Clinical Significance

PBG dysfunction or pathology is implicated in several conditions, including IgG4related sclerosing cholangitis, primary sclerosing cholangitis, hepatolithiasis (via mucin hypersecretion), and biliary neoplasms such as intraductal papillary neoplasm and cholangiocarcinoma.

PBGs develop during the late fetal period and complete maturation approximately 15 years after birth.