ampulla of Vater

The ampulla of Vater (hepatopancreatic ampulla) is formed by the confluence of the common bile duct and the main pancreatic duct just before they enter the duodenum. It opens into the descending duodenum at the major duodenal papilla, typically located along the posteromedial wall. The sphincter of Oddi, a smooth muscle sphincter complex, surrounds the ampulla and separately controls the terminal common bile duct, pancreatic duct, and the ampulla itself, regulating the release of bile and pancreatic enzymes in response to hormonal (CCK) and neural signals during digestion.

Clinical significance: Obstruction at the ampulla (e.g., by gallstones, tumors, or strictures) causes simultaneous biliary and pancreatic outflow obstruction, leading to obstructive jaundice, elevated conjugated bilirubin, and potentially acute pancreatitis (gallstone pancreatitis). Ampullary carcinoma, though rare, often presents earlier than pancreatic head cancer due to early biliary obstruction, causing painless jaundice, and may cause a positive "Courvoisier sign" (palpable, non-tender gallbladder). Tumors here can sometimes cause silver-colored stools (combination of acholic stool and GI bleeding) - a classic but rare finding. Endoscopic retrograde cholangiopancreatography (ERCP) is used to visualize and access the ampulla for diagnosis and treatment (e.g., sphincterotomy, stone extraction, stent placement). Sphincter of Oddi dysfunction can cause biliary-type pain and recurrent pancreatitis without obstruction.

Embryologically, the ventral pancreatic bud rotates to fuse with the dorsal pancreatic bud, and their duct systems join near the ampulla; anomalies like pancreas divisum result when this fusion fails, with the minor papilla (Santorini duct) becoming the dominant pancreatic drainage site.