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.

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