Duodenum- Duodenal Relations-The first part of the duodenum-second part of the duodenum-The third part of the duodenum-The fourth part of the duodenum-Trauma to the Duodenum-Duodenal Ulcer

Duodenum

Description

The duodenum is a C-shaped tube, about25 cm (10 in.) long, which joins the stomach to the jejunum. It receives the openings of the bile and pancreatic ducts. The duodenum curves around the head of the pancreas

 Duodenal Relations

The duodenum is situated in the epigastric and umbilical regions and, for purposes of description, is divided into four parts.

 

The first part of the duodenum

it begins at the pylorus and runs upward and backward on the transpyloric plane at the level of the 1st lumbar vertebra

The relations of this part are as follows:

■■ Anteriorly: The quadrate lobe of the liver and the gallbladder

■■ Posteriorly: The lesser sac (first inch only), the gastroduodenal artery, the bile duct and the portal vein, and the inferior vena cava

■■ Superiorly: The entrance into the lesser sac (the epiploic foramen)

■■ Inferiorly: The head of the pancreas


The second part of the duodenum

runs vertically downward in front of the hilum of the right kidney on the right side of the 2nd and 3rd lumbar vertebrae. About halfway down its medial border, the bile duct and the main pancreatic duct pierce the duodenal wall. They unite to form the ampulla that opens on the summit of the major duodenal papilla. The accessory pancreatic duct, if present, opens into the duodenum a little higher up on the minor duodenal papilla.

The relations of this part are as follows:

■■ Anteriorly: The fundus of the gallbladder and the right lobe of the liver, the transverse colon, and the coils of the small intestine

■■ Posteriorly: The hilum of the right kidney and the right ureter

■■ Laterally: The ascending colon, the right colic flexure, and the right lobe of the liver

■■ Medially: The head of the pancreas, the bile duct, and the main pancreatic duct


The third part of the duodenum

it runs horizontally to the left on the subcostal plane, passing in front of the vertebral column and following the lower margin of the head of the pancreas

The relations of this part are as follows:

■■ Anteriorly: The root of the mesentery of the small intestine, the superior mesenteric vessels contained within it, and coils of jejunum

■■ Posteriorly: The right ureter, the right psoas muscle, the inferior vena cava, and the aorta

■■ Superiorly: The head of the pancreas

■■ Inferiorly: Coils of jejunum Fourth Part of the Duodenum

The fourth part of the duodenum

it runs upward and to the left to the duodenojejunal flexure .The flexure is held in position by a peritoneal fold, the ligament of Treitz, which is attached to the right crus of the diaphragm. The relations of this part are as follows:

■■ Anteriorly: The beginning of the root of the mesentery and coils of jejunum

■■ Posteriorly: The left margin of the aorta and the medial border of the left psoas muscle

Trauma to the Duodenum

Apart from the first inch, the duodenum is rigidly fixed to the posterior abdominal wall by peritoneum and therefore cannot move away from crush injuries. In severe crush injuries to the anterior abdominal wall, the third part of the duodenum may be severely crushed or torn against the third lumbar vertebra.

 

Duodenal Ulcer

As the stomach empties its contents into the duodenum, the acid chyme is squirted against the anterolateral wall of the first part of the duodenum. This is thought to be an important factor in the production of a duodenal ulcer at this site. An ulcer of the anterior wall of the first inch of the duodenum may perforate into the upper part of the greater sac, above the transverse colon. The transverse colon directs the escaping fluid into the right lateral paracolic gutter and thus down to the right iliac fossa. The differential diagnosis between a perforated duodenal ulcer and a perforated appendix may be difficult. An ulcer of the posterior wall of the first part of the duodenum may penetrate the wall and erode the relatively large gastroduodenal artery, causing a severe hemorrhage. The gastroduodenal artery is a branch of the hepatic artery, a branch of the celiac trunk.