Ultrasound of Abdominal Aorta ACR Practice Parameters 2015

An abdominal ultrasound is performed to evaluate abdominal structures, including the abdominal aorta. It may be used to check for a number of conditions. It's often the screening method of choice for detecting an abdominal aortic aneurysm, a weakened, bulging spot in the abdominal aorta, the artery that runs through the middle of your abdomen and supplies blood to the lower half of your body.An abdominal ultrasound to screen for an abdominal aortic aneurysm is recommended for men ages 65 to 75 who are current or former cigarette smokers. Having an abdominal ultrasound to screen for an abdominal aortic aneurysm isn't specifically recommended for men who have never smoked, nor women, unless your doctor suspects you may have an aneurysm.

The American College of Radiology (ACR), in its revised resolution of 2015, came out with practice parameter for the performance of diagnostic and screening ultrasound of the abdominal aorta in adults.

Following are the indication/contradictions and specific recommendations:-

INDICATIONS/ CONTRADICTIONS

Indications for ultrasound of the abdominal aorta include, but are not limited to, the following:

A. Diagnostic Evaluation for Abdominal Aortic Aneurysm

1. Palpable or pulsatile abdominal mass or abdominal bruit

2. Unexplained lower back pain, flank pain, or abdominal pain

3. Follow-up of a previously demonstrated abdominal aortic aneurysm

4. Follow-up of patients with an abdominal aortic and/or iliac endoluminal stent graft

B. Screening Evaluation for Abdominal Aortic Aneurysm

1. Men age 65 or older

2. Women age 65 or older with cardiovascular risk factors

3. Patients age 50 or older with a family history of aortic and/or peripheral vascular aneurysmal disease

4. Patients with a personal history of peripheral vascular aneurysmal disease

Groups with additional risk include patients with a history of smoking, hypertension, or certain connective tissue diseases (eg, Marfan syndrome). There are no absolute contraindications to ultrasound of the aorta. If aortic rupture or dissection is clinically suspected, ultrasound is usually not the examination of choice

SPECIFICATIONS OF THE EXAMINATION

A. Diagnostic Examination

The examination includes the following, when feasible:

1. Abdominal aorta

a. Longitudinal images (along the long axis of the vessel)

i. Proximal (below diaphragm, near the celiac artery) ii. Mid (near the level of the renal arteries) iii. Distal (above the iliac bifurcation) iv. The aorta should be imaged in the plane that is parallel to the long axis of the lumen (for measurement of the AP dimension) and perpendicular to the long axis of the lumen (for measurement of the transverse dimension). The transverse measurement may also be obtained in the coronal plane [5].

b. Transverse images (perpendicular to the long axis of the vessel)

i. Proximal (below diaphragm, near the celiac artery) ii. Mid (near the level of the renal arteries) iii. Distal (above the iliac bifurcation)

c. Measurements

i. Measurements of the proximal, mid, and distal aorta should be obtained using predominantly the long axis view to measure the AP dimension. Transverse or coronal views should also be obtained to measure the width. Measurements are taken at the greatest diameter of the aorta, from outer edge to outer edge. ii. If an aneurysm is present, the maximal size and location of the aneurysm should be documented and recorded. The relationship of the dilated segment to the renal arteries and to the aortic bifurcation should be determined if possible. iii. At a minimum, the largest measurement should be recorded and reported. A measurement of the length of the aneurysm is not necessary.

2. Common iliac arteries

a. Longitudinal images of the proximal right and left common iliac arteries (along the long axis of the vessel) 4 / Abdominal Aorta Ultrasound PRACTICE PARAMETER

b. Transverse images (perpendicular to the long axis of the vessel) of the proximal common iliac arteries, just below the bifurcation

c. Measurement of the widest visualized portion of each common iliac artery, from outer edge to outer edge

Color Doppler imaging and/or spectral Doppler with waveform analysis of the aorta and iliac arteries may be helpful to demonstrate patency and the presence of intraluminal thrombus.

After endoluminal graft placement, color (or power) and spectral Doppler are required to document the presence or absence of endoleaks.

Inter observer measurements of an aortic aneurysm can vary by as much as 5 mm. Visual comparison with prior studies is recommended to ensure measurements are obtained at similar locations and to assess for interval change in aneurysm size. Consistent measurements of aneurysm diameter are recommended following endograft repair to check for interval enlargement in sac size [6].

B. Screening Examination for Abdominal Aortic Aneurysm

1. Abdominal aorta

a. Longitudinal images (along the long axis of the vessel) i. Proximal (below diaphragm, near the celiac artery) ii. Mid (near the level of the renal arteries) iii. Distal (above the iliac bifurcation)

b. Transverse images (perpendicular to the long axis of the vessel) i. Proximal (below diaphragm, near the celiac artery) ii. Mid (near the level of the renal arteries) iii. Distal (above the iliac bifurcation)

c. Measurements

AP measurements of the aorta sufficient to determine if an aortic aneurysm exists according to the criteria in section V.A. above should be obtained. If an aneurysm is present, its greatest dimension should be reported. However, if no aneurysm is identified, the largest diameter of the abdominal aorta should be reported.

C. Interpretation of the Screening Examination Should Include at Least 3 Categories

1. Positive – Infrarenal abdominal aortic aneurysm greater than or equal to 3 cm in diameter or greater than or equal to 1.5 times the diameter of the more proximal infrarenal aorta [7]. The latter definition is particularly important in women and small adults [8].

2. Negative – No infrarenal abdominal aortic aneurysm

3. Indeterminate – Aneurysmal status not defined because of nonvisualization or partial visualization of the infrarenal abdominal aorta

4. The report should also state whether or not the suprarenal aorta was seen and, if seen, should reflect whether or not it is normal. The report should also state whether dilation of the aorta above the celiac artery is noted. For the area above the celiac artery, an aneurysm may be reported if the diameter is greater than 3.9 cm for males or 3.1 cm for females.

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