GREAT RESOURCES FOR RESIDENCY
ABDOMINAL AORTIC ANEURYSM SCREENING
AAA SCREENING
Definition
AAA is defined as a dilated aorta with a diameter at least 1.5 times the diameter measured at the level of the renal arteries.
In most individuals, the diameter of the normal abdominal aorta is approximately 2.0 cm (range 1.4 to 3.0 cm).
For practical purposes, an AAA is diagnosed when the aortic diameter exceeds 3.0 cm.
Indications for screening according to USPSTF
Men aged 65-75 years who have ever smoked (smoking defined as >100 cigarettes in lifetime).
Men aged 65-75 years who have never smoked can selectively be offered screening based on the patient's medical history, family history, other risk factors, and personal values.
What test to perform?
One-time abdominal ultrasound. US is considered the screening modality of choice for AAAs because of its high sensitivity and specificity, as well as its safety and relatively low cost.
If, for whatever reason, your patient had a CT abdomen and pelvis with or without contrast between ages 65-75 years that showed no AAA, you probably do not need to obtain an ultrasound (of note, this observation is based on this study). This also applies for MRI.
Follow-up algorithm
Aortic diameter <2.6 cm: Re-screening is not recommended
Aortic diameter 2.6-2.9 cm: Follow-up imaging at 5-year intervals is recommended
Aortic diameter 3.0-3.4 cm: Follow-up imaging at 3-year intervals is recommended
Aortic diameter 3.5-4.4 cm: Follow-up imaging at 12-month intervals is recommended
Aortic diameter 4.5-5.4 cm: Follow-up imaging at 6-month intervals is recommended
Aortic diameter ≥5.5 cm: Surgical repair is recommended
What are the benefits?
One-time screening with US for AAA has been shown to be effective in reducing AAA-related mortality and AAA rupture in men 65 years and older. It is also associated with increased elective AAA operations and decreased emergency AAA operations.
What are the harms?
Psychological distress, particularly for patients with small AAAs that do not require immediate intervention and will likely never cause harm.
Adverse outcomes from management of the AAA. The perioperative (30-day) mortality rate with elective AAA repair in major randomized trials varied from 2.7 to 5.8 percent, depending upon comorbidity factors and the type of procedure.
Medicare Coverage
Males between 65 and 75 years of age who smoked at least 100 cigarettes.
Males or females with a family history of AAA.
Bibliography
USPSTF Guidelines 2014
Surveillance intervals for small AAAs JAMA 2013
Check Uptodate, has a good and relatively brief article on this topic.