At this point, it turns abruptly forward to merge with the jejunum, forming the duodenojejunal flexure.

[3] The duodenojejunal flexure is surrounded by the suspensory muscle of the duodenum.

It 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 during abdominal surgery.

[6]: 85 This article incorporates text in the public domain from page 1170 of the 20th edition of Gray's Anatomy (1918)