Duodenojejunal Flexure Presented, Anterior View

Description

Arising in the left upper quadrant, the fourth (ascending) part of the duodenum runs superiorly and leftward to the duodenojejunal flexure, where it turns abruptly into the proximal jejunum. The flexure sits left of the midline at about the level of L2, posterior to the transverse colon and its mesentery, and just inferior to the body of the pancreas. A frontal (anterior) view typically allows the junction to be appreciated as a fixed, sharp angle compared with the more mobile jejunal loops distal to it. Short. Identification of the duodenojejunal junction matters because it marks the transition from retroperitoneal duodenum to intraperitoneal jejunum, a change that defines mobility, peritoneal relationships, and the pattern of spread for hemorrhage or perforation. The suspensory ligament of the duodenum (ligament of Treitz) inserts at the flexure, tethering it to the right crus of the diaphragm and adjacent connective tissue, so this point becomes a dependable surgical and radiologic landmark when orienting bowel in malrotation, internal hernia near the ligament, or when defining the upper border of the jejunum during a Roux-en-Y reconstruction. A long glance at this angle clarifies why a proximal small-bowel obstruction can localize here and why the left paraduodenal fossa is a known trap for herniation. Educators will find this image well suited for gross anatomy teaching on peritoneal reflections and mesenteric root orientation, and for GI modules that introduce the ligament of Treitz as a landmark separating upper from lower gastrointestinal bleeding. It also fits surgical atlases and radiology teaching files that correlate frontal anatomy with fluoroscopy or CT when confirming the position of the duodenojejunal flexure in suspected malrotation. Anatomical accuracy verified by SciePro's Medical Advisory Board.