Browse the corpus

The duodenum comprises the initial C-shaped segment of the small intestine, coursing from the pylorus to the jejunum and measuring approximately 25 to 30 cm. Positioned inferior to the stomach, this segment represents the shortest and widest portion of the small intestine. Four parts are recognized: the duodenal bulb, descending, horizontal, and ascending segments, which closely relate to the liver, pancreas, aorta, inferior vena cava (IVC), and superior mesenteric vessels. Except for the 1st segment, the duodenum occupies a retroperitoneal position, anchored against the posterior abdominal wall. The duodenal wall consists of mucosa, submucosa, muscularis, and serosa, enabling digestion, mixing of chyme, and regulated transit while receiving biliary and pancreatic secretions. Duodenal anatomy carries major medical and surgical significance due to the proximity of this gut segment to crucial vascular and biliary structures. The major duodenal papilla serves as a critical landmark during endoscopic retrograde cholangiopancreatography and biliary interventions (see Image. Anatomy of the Pancreaticobiliary Junction). Congenital and acquired disorders, including duodenal atresia, superior mesenteric artery (SMA) syndrome, and peptic ulcer disease, reflect the importance of regional relationships and vascular supply. Precise understanding of duodenal structure and physiology supports timely diagnosis, procedural safety, and prevention of life-threatening complications.