What are the current recommendations for screening, surveillance, and management of abdominal aortic aneurysm, including age and risk criteria, preferred imaging modality, size thresholds for repair, and medical therapy?

Abdominal Aortic Aneurysm: Screening, Surveillance, and Management

All men aged 65-75 who have ever smoked should receive one-time ultrasound screening for AAA, as this reduces AAA-specific mortality by approximately 50%. 1, 2

Screening Recommendations by Population

Men aged 65-75 who have ever smoked (≥100 cigarettes lifetime)

• Perform one-time ultrasound screening (Grade B recommendation) 1
• This is the highest-yield screening population, with number needed to screen of 500 to prevent one AAA-related death over 5 years 1
• Ultrasound should be performed in an accredited facility with credentialed technologists 1, 2

Men aged 65-75 who have never smoked

• Selectively offer screening rather than routine screening for all (Grade C recommendation) 1
• Consider screening if additional risk factors present: family history of AAA, coronary artery disease, peripheral artery disease, or hypertension 3
• Number needed to screen is 1,783 to prevent one death, making universal screening less beneficial 1

Women aged 65-75 who have ever smoked

• Insufficient evidence to recommend for or against screening (I Statement) 1, 2
• Women have four-fold higher rupture risk than men at similar aneurysm sizes, but lower overall AAA prevalence 4

Women who have never smoked

• Do not screen routinely (Grade D recommendation) 1
• AAA is extremely rare in this population (prevalence 2-6.2%), and harms outweigh benefits 1

Special populations requiring screening

• First-degree relatives of AAA patients aged ≥50 years should undergo screening 2
• Men aged ≥60 who are siblings or offspring of AAA patients should receive physical examination and ultrasound 4

Imaging Modality

Primary screening tool

• Ultrasound is the screening modality of choice with 95-100% sensitivity and specificity 2, 5
• Non-invasive, safe, cost-effective, and requires no contrast or radiation 5
• Fails to visualize the aorta adequately in only 1-2% of cases due to bowel gas or obesity 2

Alternative imaging

• Non-contrast CT can be considered when ultrasound is inadequate (obesity, poor sonographic window), with 83-89% sensitivity 1
• CT angiography is the gold standard for preoperative planning when repair thresholds are reached 4

Surveillance Protocol Based on Size

AAA definition

• Infrarenal aortic diameter ≥3.0 cm or >1.5 times the adjacent normal segment 1, 4

Size-based surveillance intervals (using duplex ultrasound)

For men: 4

• 3.0-3.9 cm: Every 3 years
• 4.0-4.9 cm: Annually
• 5.0-5.4 cm: Every 6 months

For women: 4

• 3.0-3.9 cm: Every 3 years
• 4.0-4.4 cm: Annually
• 4.5-5.0 cm: Every 6 months

Accelerated surveillance

• Shorten surveillance intervals if rapid growth occurs: ≥10 mm per year or ≥5 mm per 6 months 4
• Use CT or MRI if ultrasound does not allow adequate measurement 4

Surgical Repair Thresholds

Size-based thresholds for elective repair

• Men: ≥5.5 cm diameter 1, 4
• Women: ≥5.0 cm diameter 4
• These thresholds are based on when rupture risk exceeds operative risk (annual rupture risk <5 cm is only 0.5-5%) 4

Additional indications for repair regardless of size

• Symptomatic AAA (abdominal or back pain attributable to aneurysm) 4
• Rapid expansion: ≥0.5 cm in 6 months or ≥1 cm per year 4
• Saccular morphology (higher rupture risk at smaller sizes) 4

Contraindication to repair

• Do not repair AAA in patients with limited life expectancy (<2 years) 4

Medical Management

Cardiovascular risk modification (primary focus)

• The 10-year risk of death from cardiovascular causes is up to 15 times higher than aorta-related death in AAA patients 4
• Medical management focuses on reducing major adverse cardiovascular events, not preventing aneurysm growth 4

Specific interventions

Smoking cessation (most critical modifiable risk factor): 4

• Behavior modification, nicotine replacement, or bupropion
• Smoking is associated with aneurysm growth and rupture risk 6

Blood pressure control: 4

• Target aggressive hypertension management
• Hypertension is associated with AAA expansion and rupture 6

Lipid management: 4

• Intensive lipid management to LDL-C target <55 mg/dL (<1.4 mmol/L)

Antiplatelet therapy: 4

• Consider low-dose aspirin if concomitant coronary artery disease present
• Aspirin is not associated with higher AAA rupture risk 4

Medications to avoid

• Fluoroquinolones should be generally discouraged for patients with aortic aneurysms, used only if compelling indication with no reasonable alternative 4

Repair Technique Selection

Endovascular repair (EVAR)

• EVAR reduces peri-operative mortality to <1% compared to open repair 4
• Preferred for ruptured AAA with suitable anatomy to reduce peri-operative morbidity and mortality 4

Post-EVAR surveillance

• Imaging at 1 month and 12 months post-operatively 4
• Duplex ultrasound is 95% accurate for measuring sac diameter and 100% specific for detecting type I and III endoleaks 4
• Consider CT or MRI every 5 years when duplex ultrasound used for routine surveillance 4

Common Pitfalls to Avoid

Screening underutilization

• Screening rates in eligible populations are only 13-26% despite clear mortality benefit 2
• Actively identify and screen all men aged 65-75 with smoking history

Ignoring family history

• Not considering family history as important risk factor that may warrant screening outside standard guidelines 2
• Screen first-degree relatives aged ≥50 years 2

Misunderstanding surveillance priorities

• Focus is on cardiovascular risk reduction, not aneurysm growth prevention 4
• Patients are more likely to die from cardiovascular disease than aneurysm rupture 4

Premature intervention

• Multiple randomized trials (UKSAT, ADAM, CAESAR, PIVOTAL) showed no survival benefit from early repair of AAAs measuring 4.0-5.4 cm compared to surveillance 4
• Adhere to size thresholds unless rapid growth or symptoms develop