Duodenojejunal junction

The duodenojejunal junction is the border between the duodenum and the jejunum.

The ascending portion of the duodenum ascends on the left side of the aorta, as far as the level of the upper border of the second lumbar vertebra, where it turns abruptly forward to become the jejunum, forming the duodenojejunal junction. The duodenojejunal junction is surrounded by the suspensory muscle of the duodenum. It lies in front of the left Psoas major and left renal vessels, and is covered in front, and partly at the sides, by peritoneum continuous with the left portion of the mesentery.

The ligament of Treitz, a peritoneal fold, from the right crus of diaphragm, is an identification point for the duodenojejunal flexure.