Focused questions for aorta ultrasound the questions

Focused questions for aorta ultrasound
The questions for aorta ultrasound are as follows:
1. Is the abdominal aorta > 3 cm in diameter?
2. Are the iliac arteries > 1.5 cm in diameter?
If the answers to these questions are no, then the aorta ultrasound evalu-
ation is normal. However, one must be careful to examine the entire length
of the abdominal aorta and to evaluate in two planes, as described in this
chapter.
If the answer to either of these questions is yes, then an aneurysm has been
diagnosed, and the physician’s next step depends on the clinical picture of
the patient. A vascular surgeon should be called immediately for unstable
patients and operative repair expedited. For stable but symptomatic patients,
further evaluation with a CT scan can be arranged to better define anatomy
and facilitate operative repair. Outpatient referral for vascular surgery evalu-
ation can be arranged if the aneurysm is asymptomatic and the diameter
is < 5 cm [ 3 –5].
Diagnostic ultrasound 115
Abdominal aorta ultrasound

Anatomy
The normal abdominal aorta ( Figure 5.1 ) has a proximal-to-distal taper, and
a loss of that taper with a diameter > 3 cm indicates the presence of an AAA.
An iliac diameter > 1.5 cm is indicative of an iliac aneurysm. All measure-
ments are from outer wall to outer wall (it is better to overestimate in this
case than underestimate!). Significant abdominal aneurysms (i.e., high risk of
rupture) are ordinarily ± 5 cm in diameter, with a fusiform shape [ 5 ]. Much
research has been done to correlate diameter with risk of rupture: AAAs
< 4 cm have a 2% per year risk of rupture, AAAs 4–5 cm have a 3–12% per
year risk of rupture, and AAAs > 5 cm have a 25–41% risk of rupture [ 2 ].
Technique
Probe selection
Using a standard 3.5 MHz transducer, the abdominal aorta can usually be
visualized in its entirety – down to the iliacs. A curvilinear-array probe will
often give the best penetration, especially in patients with a larger body habitus.
Views
We recommend that the entire length of the aorta should be imaged in real
time for a complete exam. In order to document these findings, it is helpful to
specifically image the following five areas:
Diaphragm
Left gastric a.
Splenic a.
Superior mesenteric a.
Testicular a. (spermatic)
or Ovarian a.
Interior mesenteric a.
Common iliac a.
Internal iliac a.
External iliac a.
Celiac trunk
Hepatic a.
Renal a.
Lumbar a.
Median sacral a.
Figure 5.1
Normal anatomy of the abdominal aorta.
116 Diagnostic ultrasound
Abdominal aorta ultrasound

1. Transverse view of the proximal aorta
2. Transverse view of the mid aorta
3. Transverse view of the distal aorta
4. Transverse view of the distal aorta showing the bifurcation into both
iliac arteries
5. Longitudinal/sagittal view of the aorta
The most helpful landmark for aorta scanning is the vertebral body shadow –
remember that both the aorta and the vena cava will be just anterior to
the vertebrae. The aorta will be a bright white circle filled with black located
right on top of the vertebral body. One common mistake is to set the depth on
the ultrasound machine too shallow to find the vertebrae. It is recommended