What is the management and treatment for an abdominal (abdominal aortic) aneurysm?

Management and Treatment of Abdominal Aortic Aneurysm

For small AAAs (<5.5 cm in men, <5.0 cm in women), surveillance with ultrasound at size-based intervals is the standard approach, while surgical repair (preferably endovascular) is indicated when diameter reaches ≥5.5 cm in men or ≥5.0 cm in women, as the rupture risk at smaller sizes does not justify operative mortality. 1, 2

Surveillance Strategy for Small Aneurysms

The management algorithm is driven entirely by aneurysm diameter, with sex-specific thresholds:

Size-Based Surveillance Intervals:

• 3.0-3.9 cm: Ultrasound every 3 years 3, 1
• 4.0-4.4 cm (women) or 4.0-4.9 cm (men): Annual ultrasound 1, 2
• 4.5-5.0 cm (women) or 5.0-5.5 cm (men): Ultrasound every 6 months 1, 2

Duplex ultrasound is the recommended surveillance modality due to 100% specificity and positive predictive value, though CT angiography becomes mandatory when repair thresholds are approached for surgical planning 1. If ultrasound cannot adequately measure the aneurysm, cardiovascular CT or MRI should be used 1.

Critical point: Women have four-fold higher rupture risk than men at similar aneurysm sizes, justifying the lower 5.0 cm repair threshold 1. Multiple randomized trials (UKSAT, ADAM, CAESAR, PIVOTAL) demonstrated no survival benefit from early repair of AAAs measuring 4.0-5.4 cm compared to surveillance 2.

Triggers for Immediate Surgical Referral

Refer to vascular surgery when any of these conditions are met:

• Diameter threshold: ≥5.5 cm (men) or ≥5.0 cm (women) 1, 2
• Rapid expansion: ≥10 mm per year or ≥5 mm in 6 months 1, 2
• Symptomatic AAA: Any abdominal or back pain attributable to the aneurysm, regardless of size 2
• Saccular morphology: ≥4.5 cm due to higher rupture risk 1, 2

The annual rupture risk for aneurysms <5 cm is only 0.5-5%, making operative risk exceed rupture risk below these thresholds 2.

Choice of Repair Technique

Endovascular aneurysm repair (EVAR) is the preferred approach for patients with suitable anatomy and life expectancy >2 years, reducing perioperative mortality to <1% compared to open repair. 2, 4

EVAR is appropriate when:

• Suitable anatomy exists (adequate proximal neck, acceptable iliac access) 2
• Patient can comply with mandatory lifelong post-EVAR surveillance 2
• Life expectancy exceeds 2 years 2

Open surgical repair is indicated when:

• Anatomy is unsuitable for EVAR (extensive mural thrombus >90% of proximal neck circumference increases endoleak/migration risk) 4
• Patient cannot comply with post-EVAR surveillance requirements 2
• Young patients with long life expectancy where durability is paramount 2
• Failed prior EVAR 4

For ruptured AAA with suitable anatomy, endovascular repair is preferred over open repair to reduce perioperative morbidity and mortality 2, 4.

Essential Medical Management

All AAA patients require aggressive cardiovascular risk factor modification, as the 10-year risk of death from cardiovascular causes is up to 15 times higher than the risk of aorta-related death. 1

Mandatory interventions:

• Smoking cessation: The single most important modifiable risk factor for aneurysm growth and rupture 2
• Blood pressure control: Target systolic BP <120 mmHg 2
• Antiplatelet therapy: Consider low-dose aspirin if concomitant coronary artery disease is present (odds ratio 2.99) 1
• Avoid fluoroquinolones: Generally discouraged unless compelling indication with no reasonable alternative 1, 2

Low-dose aspirin is not associated with higher AAA rupture risk but could worsen prognosis if rupture occurs 1.

Post-EVAR Surveillance Protocol

Surveillance at 1 month and 12 months post-EVAR is mandatory, with the 6-month interval eliminated if 1-month imaging shows no concerning findings. 1

• 30-day imaging: Contrast-enhanced CT plus duplex ultrasound to assess intervention success 2, 4
• Follow-up schedule: 1 month, 12 months, then yearly until fifth post-operative year 2, 4
• Duplex ultrasound accuracy: 95% for measuring sac diameter and 100% specific for detecting type I and III endoleaks 1
• Long-term surveillance: CT or MRI every 5 years is reasonable when duplex ultrasound is used for routine surveillance 1

Immediate re-intervention is required for Type I or Type III endoleaks to achieve seal and prevent rupture. 2, 4

Management of Ruptured AAA

For hemodynamically unstable patients with suspected rupture:

• Permissive hypotension strategy: Target systolic BP <120 mmHg to decrease bleeding rate until definitive treatment 2
• Anti-impulse therapy: Intravenous beta-blockers as first-line agents, targeting heart rate 60-80 bpm 2
• Immediate surgical intervention: Endovascular repair preferred if anatomy suitable 2

For hemodynamically stable patients, obtain CT imaging to evaluate suitability for endovascular repair before proceeding 2.

Screening Recommendations

Men ages 65-75 who smoke or have ever smoked should receive one-time AAA screening with ultrasound, which reduces risk of dying from ruptured AAA by approximately 50%. 3, 2

• Consider screening: Men ages 65-75 who have never smoked (limited benefit) 3
• Insufficient evidence: Women ages 65-75 who smoke or have ever smoked 3
• Do not screen: Women who have never smoked 3

An "ever smoker" is defined as someone who has smoked at least 100 cigarettes in their lifetime 3.

Common Pitfalls to Avoid

Do not delay referral for symptomatic AAAs regardless of size - any abdominal or back pain attributable to the aneurysm warrants immediate vascular surgery consultation, as symptoms indicate impending rupture 2.

Do not use diameter alone in tortuous aneurysms - measure diameter perpendicular to the longitudinal axis using 3D multiplanar reformatted images to avoid overestimation 1.

Do not forget to screen for concomitant aneurysms - up to 27% of AAA patients have thoracic aneurysms, and up to 14% have femoral or popliteal aneurysms 1. Duplex ultrasound of the femoro-popliteal segment is recommended 2, 4.