Ascending Part of the Duodenum, Posterior View

Description

Arising from the horizontal (third) part, the ascending (fourth) part of the duodenum is shown coursing superiorly and slightly to the left to reach the duodenojejunal flexure. From a posterior perspective, the retroperitoneal surface sits directly anterior to the abdominal aorta, with the inferior vena cava positioned to the right of midline and posterior to the duodenum. The left psoas major forms a muscular bed laterally, while the root of the mesentery begins at the duodenojejunal junction and passes obliquely toward the right iliac fossa. Ligament of Treitz. A key landmark. This posterior anatomy matters because the fourth part of the duodenum is fixed by the suspensory muscle of the duodenum (ligament of Treitz), making it an anchor point when teaching peritoneal reflections and the transition from retroperitoneal to intraperitoneal small bowel. Radiologists and surgeons both use the duodenojejunal flexure as a positional reference on CT and upper GI series, and malrotation is often suspected when the junction fails to lie left of the spine at approximately the level of the duodenal bulb. In trauma and pancreatic surgery discussions, the proximity to the aorta and adjacent retroperitoneal planes clarifies why duodenal injuries can track posteriorly and why mobilization maneuvers must respect these vessels. Ideal for GI anatomy teaching in medical and PA curricula, and for surgical atlases covering duodenal mobilization, malrotation workup, or interpretation of cross-sectional imaging landmarks around the duodenojejunal junction. It also supports patient-education graphics that explain why upper small-bowel obstruction symptoms may relate to fixed segments near the ligament of Treitz. Anatomical accuracy verified by SciePro's Medical Advisory Board.