Gallstones enter the common bile duct and lodge at the ampulla of Vater.The gallstones obstruct the flow of the pancreatic juice or causing a reflux of bile from the common bile duct into the pancreatic duct. The powerful enzymes within the pancreas are activated. Normally, these enzymes remain in an inactive form until the pancreatic secretions reach the lumen of the duodenum.. Activation of enzymes can lead to vasodilation, increased vascular permeability, necrosis, erosion, and hemorrhage. These enzymes enter the bile duct,