Third part of duodenum

A 70-year-old man is undergoing an elective open repair of an infrarenal abdominal aortic aneurysm.
Which one of the following structures is most adherent to the aneurysm neck?

1.Left renal vein
2.Neck of pancreas
3.Third part of duodenum
4.Portal vein
5.Pylorus of stomach

While dissecting the neck of the aneurysm to put on a clamp, the third part of the duodenum is the most vulnerable. It is particularly in danger in an inflammatory aneurysm, where the duodenum is extremely adherent to the neck.

The abdominal aorta is a retroperitoneal structure. It enters the abdomen at the level of T12 through the aortic hiatus of the diaphragm and terminates at the level of L4 when it bifurcates into paired common iliac arteries. It courses just to the left of the midline and descends anterior to the bodies of the L1 to L4 vertebrae and the anterior longitudinal ligament.

Anteriorly, the abdominal aorta is closely related to a number of upper abdominal structures. Intra-operatively, these structures usually have to be retracted or dissected to allow access to the aorta. During aortic aneurysm surgery, after division of the ligament of Treitz, the 3rd part of the duodenum is dissected off the neck of the aneurysm and the duodenum retracted to the right to allow adequate exposure. The left renal vein and pancreas may also need to be retracted superiorly to expose the aneurysm neck. The left ureter may be dangerously adherent to the aneurysmal sac making it liable to iatrogenic damage.