Demonstration of the third and fourth parts of the duodenum# using the upper digestive endoscopy#

Structure of the duodenum#: The duodenum is a 25–38 cm (12-15 inch) C-shaped structure lying adjacent to the stomach. Divisions: It is divided anatomically into four sections. The first part of the duodenum lies within the peritoneum The other parts are retroperitoneal. The first part (superior part or duodenal bulb or duodenal cap), 5 cm Course: continuation from the pylorus to trans pyloric plane. It is superior to the rest of the segments, at the vertebral level of L1 It is slightly dilated. The duodenal bulb is a remnant of the mesoduodenum, a mesentery which suspends the organ from the posterior abdominal wall in fetal life. It is mobile and connected to the liver by the hepatoduodenal ligament of the lesser omentum. It ends at the superior duodenal flexure. The second part (descending part) (10cm) course: it begins at the superior duodenal flexure. It goes inferior to the lower border of vertebral body L3, before making a sharp turn medially into the inferior duodenal flexure. The pancreatic duct and common bile duct enter the descending duodenum, through the major duodenal papilla. The second part of the duodenum also contains the minor duodenal papilla, the entrance for the accessory pancreatic duct. It has upper and lower genu (flexure). the transverse mesocolon and transverse colon are in front, and the right kidney and inferior vena cava (IVC) are behind it. The junction between the embryological foregut and midgut lies just below the major duodenal papilla. The third part (horizontal part or inferior part), 7.5cm It begins at the inferior duodenal flexure and passes transversely to the left, passing in front of the inferior vena cava, abdominal aorta, and the vertebral column. The superior mesenteric artery and vein are anterior to the third part of the duodenum. This part may be compressed between the aorta and SMA causing superior mesenteric artery syndrome. The fourth part (ascending part), 2.5 cm it passes upward, joining with the jejunum at the duodenojejunal flexure. it is at the vertebral level L3 and may pass directly on top, or slightly to the left, of the aorta. N.B: (1) The duodenojejunal (DJ) junction Abrupt turn at the level of the L2 vertebra. Identified during surgery by the inferior mesenteric vein, which lies to its immediate left. Attached to the posterior abdominal wall by the suspensory muscle of the duodenum or the ligament of Treitz. (2) The villi in the first part of the duodenum are only three-quarters of the height of the villi below the papilla, so duodenal biopsies should be taken in the distal duodenum below the ampulla of Vater. (3) A pediatric colonoscope is typically used to examine the entire duodenum as it measures about 133 to 168 cm in length, compared to an upper endoscope’s 103 cm.