The left lobe of the liver is located anterior to the proximal abdominal aorta and can be used to help delineate this portion of the aorta.

The first large branch of the abdominal aorta is the celiac trunk, which divides into the common hepatic artery, left gastric artery, and splenic artery. The superior mesenteric artery is the next branch, followed by the left and right renal arteries, which branch off laterally.

The inferior mesenteric artery is the final branch of the abdominal aorta, a few centimeters proximal to the iliac bifurcation.

Scanning the aorta. A low frequency probe (e.g., 3.5–5 MHz) should be used to scan the aorta. Either a curvilinear or small phased-array probe is appropriate to use.

With the patient supine and the knees flexed, the scan should begin in the epigastric region and end near the umbilicus.

The aorta should be scanned in its entirety in both short and long axis for evaluation of an AAA.

When the aorta is scanned in the long axis or longitudinal plane, the probe marker should point toward the patient’s head.

When the aorta is scanned in the short axis or transverse plane, the marker should point toward the patient’s right side.

A five-point measurement of the aorta should be performed:

1. The proximal aorta (see image 1);
2. The mid-aorta (see image 2);
3. The distal aorta proximal to the aortic bifurcation (see image 3); and
4. The common iliac arteries (see image 3).

Measure the lumen of the aorta in the anterior to posterior dimension, from the outer wall to the outer wall. Measurement of the lumen (inner wall to inner wall) can lead to a false negative result because of an intraluminal clot (see image 5 and image 6).

A fifth view of the aorta in a longitudinal plane should be demonstrated including the distal aorta (see image 4), because the majority of abdominal aortic aneurysms are infra-renal in location (see image 7).