Anatomical segments
The duodenum is divided into four anatomical segments:
- First (superior) part: includes the duodenal bulb (duodenal cap / bulb). It courses superiorly, then turns posteriorly and laterally, transitioning into the second part.
- Second (descending) part: descends anterior to the right kidney. A key feature is the presence of the major duodenal papilla (ampulla of Vater / ampulla of Vater), where the pancreatic and biliary ducts open. This part is partially covered by peritoneum.
- Third (horizontal) part: turns sharply medially, passing horizontally anterior to the vertebral column.
- Fourth (ascending) part: ascends to the left of the aorta and terminates at the duodenojejunal flexure (duodenojejunal flexure) — the attachment site of the suspensory muscle of the duodenum (ligament of Treitz) (ligament of Treitz).
Normal structure and imaging features
The intestinal mucosa features characteristic circular folds (valvulae conniventes) that begin in the second part and continue throughout the rest of the small intestine. When the bowel is significantly distended, these folds may flatten on imaging.
The major duodenal papilla is located on the posteromedial wall of the descending part. On normal CT scans, it may protrude into the lumen by up to 1 cm (protrusion) and enhance with contrast similarly to the bowel wall. The sphincter of Oddi (sphincter of Oddi) is located inside the papilla, regulating the flow of bile and pancreatic juice.
Diseases of the duodenum
Pathologies of the organ are diverse and require the appropriate use of imaging modalities:
- Peptic ulcer (peptic ulceration): 95% are detected endoscopically. Radiologically, an ulcer crater appears as a barium collection, sometimes surrounded by a halo of edema and converging mucosal folds. Complications (bleeding, perforation) are diagnosed using contrast-enhanced CT (the modality of choice).
- Diverticula (diverticula): Found in 22% of individuals, most commonly in the descending part. These are saccular outpouchings of the wall that may contain gas, fluid, or oral contrast.
- Neoplasms (neoplasms):
- Benign tumors (adenomas, lipomas) are rare.
- Malignant tumors (ampullary carcinoma, adenocarcinomas) frequently cause obstruction. Characteristic CT/MRI findings include asymmetric wall thickening and luminal narrowing.
- Crohn's disease (Crohn disease): Manifests as fold thickening and, in late stages, strictures. A specific radiological sign is the pseudo-Billroth I sign.
Diagnostic imaging methods
The choice of method depends on the clinical objective:
- Endoscopy: Has largely replaced barium fluoroscopy (now considered a historical method) and remains the gold standard for detecting intraluminal pathology.
- Contrast-enhanced CT (CECT): The modality of choice in emergency settings (perforation, hemorrhage). It allows assessment of the bowel wall, surrounding adipose tissue, and the presence of pneumoperitoneum.
- Angiography: Indispensable in acute hemorrhage when the bleeding source cannot be identified endoscopically.
Briefly: answers to topical questions
Which ligaments anchor the duodenum to adjacent structures?
Sources mention the hepatoduodenal ligament and the ligament of Treitz. The hepatoduodenal ligament contains the supraduodenal segment of the common bile duct in its right margin. The fourth, ascending part of the duodenum terminates at the duodenojejunal flexure, which is associated with the ligament of Treitz.
Which arteries supply blood to the duodenum?
The blood supply to the duodenum is derived from anterior and posterior arterial arcades, as well as branches of other arteries.
- Pancreaticoduodenal arteries — the superior and inferior posterior arteries supply the posterior wall; the anterior and inferior posterior arteries contribute to the blood supply of the flexura duodenojejunalis.
- Branches of other arteries — gastroduodenal, right gastroepiploic, right gastric, and proper hepatic arteries.
- First jejunal artery — also contributes to the blood supply of the flexura duodenojejunalis.
Which organs are related to the descending part of the duodenum?
The descending part of the duodenum is located anterior to the right kidney and posterior to the transverse colon. It is also associated with the C-loop of the duodenum and the pancreas.
To which lymph nodes does lymphatic drainage from the duodenum occur?
Lymphatic drainage from the duodenum occurs into several groups of regional and collecting lymph nodes.
- Regional nodes — located in the porta hepatis, along the margins of the pancreas, and at the root of the small bowel mesentery.
- Celiac lymph nodes (nodi lymphoidei coeliaci) — serve as secondary lymphatic collectors for the superior part of the duodenum and are located near the celiac trunk.
Duodenal segments: S-D-H-A — Superior (bulb), Descending (major duodenal papilla), Horizontal (anterior to the spine), Ascending (ligament of Treitz).
Class and exam questions
In which part of the duodenum is the major duodenal papilla located?
The major duodenal papilla is located on the posteromedial surface of the second (descending) part of the duodenum.
What is the primary diagnostic imaging method when a perforated ulcer is suspected?
The modality of choice in an emergency setting is contrast-enhanced CT (CECT).
What is the "double-duct" sign?
This refers to the simultaneous dilatation of the common bile and pancreatic ducts, frequently observed on CT or MRI in ampullary or periampullary neoplasms.
What else to study on this topic
- Radiological semiotics of ulcers
- Complications of peptic ulcer disease and CT angiography protocol
- Secondary malignant lesions of the duodenum
- Trauma and intramural hematoma of the duodenum
- Vascular diseases: aortic aneurysms and fistulas
- Pancreatitis: impact on the duodenum
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