Clinical suspicion of abdominal aortic aneurysm (AAA)
Unexplained abdominal, back, or flank pain, particularly in the older patient
Unexplained hypotension
Syncope in the setting of abdominal pain
Palpable and/or pulsatile abdominal mass
CONTRAINDICATIONS
None: No contrast or radiation involved
LANDMARKS
The proximal aorta is located in the subxiphoid area
The aorta bifurcates into the iliac vessels at the level of the umbilicus
On the ultrasound display (FIGURE 12.1), first locate the vertebral body. The transverse proximal aorta is located above (anterior to) the vertebral body, to the right of the inferior vena cava (IVC), and below (posterior to) the superior mesenteric artery
TECHNIQUE
Apply ultrasond gel on the patient’s abdomen, from the xiphoid process to just distal to the umbilicus
Using a standard 3.5- to 5.0-MHz probe with the selection marker to the patient’s right, identify the proximal aorta in the epigastric area (FIGURE 12.2)
Once the aorta is identified, scan the entire length of the vessel to the iliac bifurcation at the umbilicus
Measure the vessel diameter from outer wall to outer wall to avoid underestimation
Vessel measurement in the following views permits adequate screening for AAA (FIGURE 12.3):
Transverse proximal aorta
Transverse middle aorta
Transverse distal aorta
Transverse view of iliac arteries at the bifurcation
Longitudinal aorta
If an aneurysm is detected (TABLE 12.1), its relation to the renal arteries and aortic bifurcation should be documented if possible (i.e., proximal, distal)
If the aorta is not readily identified, try the following techniques:
Apply gentle downward pressure with the probe to displace bowel gas
Increase the depth of penetration on the ultrasound display
Reimaging after several minutes may permit improved visualization as intestinal peristalsis displaces bowel
Place the patient in the right or left lateral decubitus position
Approach para-midline by directing the probe toward the spine to avoid bowel gas
Image coronally through the liver
Image inferiorly to the umbilicus and direct the probe cephalad
COMPLICATIONS
Delay in definitive surgical treatment in order to perform study. Computed tomography (CT) evaluation typically poses a greater time delay.