How should I assess and screen for abdominal aortic aneurysm in at‑risk patients?

Assessment and Screening for Abdominal Aortic Aneurysm

Screening Recommendations by Population

Men aged 65-75 who have ever smoked (≥100 cigarettes lifetime) should receive one-time ultrasound screening for AAA, as this reduces AAA-specific mortality by approximately 42-50%. 1, 2

Men 65-75 Years Who Have Ever Smoked

• Offer one-time screening with abdominal ultrasonography (Grade B recommendation) 1, 2
• This is the highest-yield population, with absolute AAA-related mortality reduction of 0.14% (from 0.33% to 0.19%) 1
• "Ever smoking" is defined as having smoked at least 100 cigarettes in one's lifetime 1

Men 65-75 Years Who Have Never Smoked

• Screening may be selectively offered, particularly if strong first-degree family history of AAA requiring surgery exists 2
• Number needed to screen is approximately 1,783 never-smokers to prevent one AAA-related death over 5 years 2
• The benefit is substantially lower than in smokers, affecting only a small proportion of this group 1

Women 65-75 Years Who Smoke or Have Ever Smoked

• Current evidence is insufficient to make a firm recommendation for or against routine screening 1
• Consider screening in healthy female smokers with first-degree family history of AAA requiring surgery 2
• AAA prevalence in women is one-sixth that of men 1, 2

Women Who Have Never Smoked

• Do not perform routine screening - AAA is extremely rare in this population and harms outweigh benefits 1, 2

Additional High-Risk Populations

• Men aged ≥60 years who are siblings or offspring of AAA patients should undergo physical examination and ultrasound screening 3
• First-degree relatives of AAA patients aged ≥50 years warrant screening consideration 4

Screening Methodology

Primary Screening Modality

• Abdominal ultrasonography is the gold standard screening method with 95% sensitivity and near 100% specificity 1, 2, 4
• Non-invasive, cost-effective, no radiation exposure, and widely available 2
• Must be performed in an accredited facility with credentialed technologists 4

Frequency of Screening

• One-time screening is sufficient - rescreening those with normal initial results provides negligible benefit 2, 4
• Death from AAA rupture after negative ultrasound at age 65 is rare, with 10-year incidence of new AAAs ranging only 0-4%, none exceeding 4.0 cm diameter 1, 2

Upper Age Limit

• Age 75 years is generally considered the upper limit for screening 2
• Beyond age 75, comorbid conditions decrease the likelihood of benefit from subsequent surgery 2

Diagnostic Criteria

AAA Definition

• Infrarenal aortic diameter ≥3.0 cm or >1.5 times the adjacent normal segment 3, 5
• Maximum diameter should be measured perpendicular to the longitudinal axis using multiplanar reformatted images to avoid overestimation in tortuous vessels 3

Management Based on Initial Screening Results

Normal Result (Aorta <3.0 cm)

• No further AAA-specific surveillance needed 1, 2

Small AAA (3.0-3.9 cm)

• Surveillance with ultrasound every 3 years 3, 4
• No evidence supports intervention at this size 1

Intermediate AAA (4.0-4.9 cm in men; 4.0-4.4 cm in women)

• Ultrasound surveillance annually 3
• Surveillance preferred over immediate surgery - randomized trials showed no mortality benefit from early repair 4

Large AAA (≥5.0 cm in women; ≥5.5 cm in men)

• Ultrasound every 6 months 3
• Refer to vascular surgery for intervention consideration 3

Critical Quality Assurance Considerations

• Ultrasound accuracy depends on adequate quality control measures - absence of quality assurance lowers test accuracy 2
• Regular quality checks are essential for maintaining screening program effectiveness 2

Common Pitfalls to Avoid

• Do not screen women who have never smoked - this represents inappropriate resource utilization with no demonstrated benefit 1, 2
• Do not perform repeat screening in patients with normal initial ultrasound results 1, 2
• Do not screen patients over age 75 with significant comorbidities limiting surgical candidacy 2
• Ensure proper ultrasound technique with perpendicular measurement to avoid overestimating diameter in tortuous aortas 3