Location and Topography
The major duodenal papilla is located on the posteromedial wall of the descending part of the duodenum (second part of the duodenum). Topographically, this corresponds to the midpoint of the descending duodenum or the junction of its middle and lower thirds.
The mucosa in this region forms permanent circular folds (plicae circulares), which span about ½ to ⅔ of the intestinal circumference. However, along the medial wall (in the lower, or less frequently upper, half of the descending segment), a prominent longitudinal fold of the duodenum (plica longitudinalis duodeni) is formed. It measures about 11 mm in length, and the major duodenal papilla sits at its distal end.
Approximately 3–4 cm superiorly, the minor duodenal papilla (papilla duodeni minor) may be found, which marks the opening of the accessory pancreatic duct (present in over 30% of individuals).
Morphology and Structure
Grossly, the structure appears as a mucosal elevation ranging from 0.2 to 2 cm in height, with an orifice diameter at its apex varying between 2.0 and 4.5 mm.
The papilla is frequently shielded superiorly by a proximal transverse mucosal fold measuring 1–2 cm in length.
Surrounding the terminal opening is the sphincter of the hepatopancreatic ampulla (m. sphincter ampullae hepatopancreaticae), commonly known as the sphincter of Oddi. This functional ring surrounds the terminal parts of both the common bile duct and the main pancreatic duct.
Duct Openings
The common bile duct and the main pancreatic duct open at the apex of the papilla:
- Common bile duct (ductus choledochus) — its intramural (interstitial) segment is about 1.6 cm long and pierces the posterior duodenal wall obliquely.
- Pancreatic duct (ductus pancreaticus) — courses through the entire pancreas from the tail to the head before reaching the papilla. Just prior to its termination, its circular muscle layer thickens to form its own sphincter (m. sphincter ductus pancreatici).
Two primary anatomical variations of duct termination exist:
- Common ampulla formation (80% of cases): The ducts unite near the right margin of the pancreatic head to form the hepatopancreatic ampulla (ampulla hepatopancreatica or biliopancreatica), which opens via a single common orifice.
- Separate openings (20% of cases): The ducts do not fuse and instead open onto the apex of the papilla via two distinct, separate orifices, one located superior to the other.
Clinical Significance
- Gastrointestinal Surgery: During the management of bleeding posterior duodenal ulcers, surgeons must be acutely aware of regional topography to avoid iatrogenic injury to the major duodenal papilla, the common bile duct, and adjacent pancreatic tissue.
- Oncology: According to standardized oncological guidelines (e.g., NCCN Guidelines), the small intestine, including the duodenum and the ampulla of Vater, has dedicated TNM staging systems for neuroendocrine and periampullary tumors.