Answer:
The duodenojejunal flexure is located anterolateral to the aorta at the level of the upper border of the second lumbar vertebra. It makes a sharp turn anteroinferiorly to become the jejunum.
The duodenojejunal flexure is suspended from the ligament of Treitz, which serves as its surgical landmark and gives it its unique shape. It also marks the small bowel's transition from the retroperitoneum, which invests the duodenum, into the peritoneal cavity.
