The duodenum is the first and shortest part of the small intestine, about 25 cm long, curving in a C shape around the head of the pancreas. It has four parts: superior, descending, horizontal and ascending. Apart from its first couple of centimetres, it is fixed to the posterior abdominal wall behind the peritoneum.
| Location | Upper abdomen, curving around the head of the pancreas from the pylorus (L1) to the duodenojejunal flexure (L2), lying over L1-L3 |
|---|---|
| Parts |
|
| Nerve Supply | Vagus nerve (parasympathetic); Coeliac and superior mesenteric plexuses (sympathetic) |
| Blood Supply | Gastroduodenal artery; Anterior and posterior superior pancreaticoduodenal arteries; Anterior and posterior inferior pancreaticoduodenal arteries; Supraduodenal artery |
| Venous drainage |
|
| Lymphatic drainage |
|
Neutralises acid chyme with alkaline secretions, mixes food with bile and pancreatic enzymes, releases secretin and cholecystokinin, and absorbs iron and calcium.
The duodenum receives bile and pancreatic juice through the major duodenal papilla, where the foregut meets the midgut, so its blood supply comes from both the coeliac trunk and the superior mesenteric artery. Most duodenal ulcers occur in the first part. Because it is retroperitoneal, duodenal injuries in blunt trauma may give few early signs and can be missed.
Peptic ulcer, usually in the first part, linked to H. pylori and NSAIDs; causes epigastric pain relieved by food and may bleed or perforate.
Congenital blockage of the duodenum causing bilious vomiting in newborns and a double bubble on X-ray, associated with Down syndrome.
Bleeding into the duodenal wall after blunt trauma, such as a bicycle handlebar injury, causing obstruction.
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