Longitudinal fold of duodenum

The longitudinal fold of duodenum is a vertical fold of mucosa produced primarily by the intramural course of the common bile duct.

As the common bile duct traverses the wall of the second part of the duodenum, it elevates the overlying mucosa to form the longitudinal fold. Near the lower end of this fold, the main pancreatic duct (duct of Wirsung) joins the common bile duct to form the hepatopancreatic ampulla (ampulla of Vater). This ampulla opens at the major duodenal papilla, which is situated at the inferior end of the longitudinal fold.