Duodenojejunal

Duodenojejunal refers to the junction between the duodenum and jejunum of the small intestine, most often described as the duodenojejunal flexure. This bend marks the transition from the fixed retroperitoneal portion of the duodenum to the relatively mobile proximal jejunum. The flexure is located in the upper abdomen, near the left of the midline at about the level of the second lumbar vertebra, though position can vary among individuals.

Support: The duodenojejunal flexure is held in position by the suspensory muscle of the duodenum, also called the ligament of Treitz. The ligament extends from the right crus of the diaphragm and surrounding connective tissue to the duodenojejunal flexure, contributing to the angle of the duodenum and helping maintain the retroperitoneal position of the second part of the duodenum.

Development: During embryology, the gut rotates and becomes fixed in the abdomen, producing the duodenojejunal junction. The attachments at the duodenojejunal flexure contribute to the proper alignment and fixation of the proximal small intestine.

Clinical relevance: The duodenojejunal flexure is a landmark in imaging and surgery. Volvulus and malrotation can involve abnormal positioning or fixation of this junction, potentially causing obstruction. In radiology, the ligament of Treitz defines the upper boundary of the small intestine and is used as a reference point in locating sources of gastrointestinal bleeding and in interpreting upper GI studies.