What are the symptoms and management of abdominal aortic aneurysm (AAA)?

Abdominal Aortic Aneurysm Symptoms and Management

Clinical Presentation

Most AAAs remain completely asymptomatic until rupture occurs, which is why they are typically discovered incidentally on imaging performed for unrelated reasons. 1, 2

Asymptomatic AAAs

• The majority (approximately two-thirds) of AAAs produce no symptoms and are detected as incidental findings on ultrasound, CT, or other abdominal imaging studies 1, 3
• Patients may have a palpable pulsatile abdominal mass on physical examination, though clinical examination sensitivity is generally poor 1

Symptomatic AAAs (High-Risk for Rupture)

When symptoms develop, they indicate impending or actual rupture and require immediate emergency department evaluation:

• Acute abdominal pain, back pain, or flank pain attributable to the AAA indicates impending rupture and necessitates ICU admission within 24-48 hours 4, 3
• Classic presentation includes acute back pain with a pulsatile abdominal mass, often associated with retroperitoneal hemorrhage 1
• Pain may be described as "sharp" or "stabbing" rather than the classic "tearing" or "ripping" quality 1
• Hypovolemic shock may occur with frank rupture 1

Uncommon Presentations

• Unilateral lower limb swelling from inferior vena cava compression with associated caval thrombosis 5
• Thromboembolization or atheroembolization to lower extremities 3
• Aortoenteric or arteriovenous fistula formation 3
• Vertebral body erosion causing neurologic deficits in chronic contained ruptures 1

Diagnostic Evaluation

Initial Screening and Surveillance

Duplex ultrasound is the standard imaging technique for AAA screening and surveillance, measuring the leading-edge to leading-edge anteroposterior diameter 1

• Ultrasound is 95% accurate for measuring aneurysm diameter and should include measurements at proximal, mid, and distal infrarenal aorta 1
• CT without contrast is diagnostically equivalent to ultrasound for AAA detection when ultrasound is not suitable 1

Pre-Intervention Imaging

When AAAs reach 5.5 cm or become symptomatic, CT angiography (CTA) is the optimal imaging modality for surgical planning due to its wide availability, accuracy, speed, and anatomic detail 1

• MR angiography is a reasonable alternative if CT cannot be performed (iodinated contrast allergy) 1
• CTA provides superior visualization of the aorta and branch vessels, especially for pre-operative planning 1

Management Strategy

Surveillance Protocol for Asymptomatic AAAs

The European Society of Cardiology provides specific surveillance intervals based on aneurysm size and sex 1:

For Men:

• 25-29 mm: Repeat imaging every 4 years 1
• 30-39 mm: Repeat imaging every 3 years 1
• 40-44 mm: Repeat imaging every 12 months 1
• 45-49 mm: Repeat imaging every 6 months 1
• ≥50 mm: Consider intervention 1

For Women:

• Same intervals as men for 25-44 mm 1
• ≥50 mm: Consider intervention (lower threshold than men due to 4-fold higher rupture risk at same diameter) 6

Medical Management

All patients with AAAs require aggressive risk factor modification 2, 3:

• Smoking cessation is critical, as tobacco use accelerates aneurysm growth 2, 3
• Blood pressure optimization with antihypertensive therapy 2, 3
• Treatment of dyslipidemia 2

Indications for Urgent Intervention

Immediate ICU admission and surgical evaluation within 24-48 hours is required for 4:

1. Symptomatic AAA (abdominal, back, or flank pain attributable to the aneurysm) 4, 3
2. Rapid expansion: ≥7 mm in 6 months or ≥10 mm in 12 months 4, 6
3. Rupture (frank or contained) 3

Indications for Elective Intervention

Surgery is generally recommended when 1, 6, 3:

• Men: AAA diameter ≥5.5 cm 1, 6
• Women: AAA diameter ≥5.0 cm (due to higher rupture risk) 6
• Saccular morphology at smaller diameters, as 25% of acute presentations occur at <5.5 cm 4

Surgical Options

Two primary repair techniques are available 1:

1. Open surgical repair: Removal of aneurysmal segment with graft replacement 1
2. Endovascular aneurysm repair (EVAR): Stent graft placement without aneurysm removal 1, 5

Emergency Management Protocol

For symptomatic or rapidly expanding AAAs 4:

• ICU admission for continuous arterial blood pressure monitoring 4
• Blood pressure control: Target normotensive BP, reducing SBP by no more than 25% within first hour, then to 160/100 mmHg within 2-6 hours if stable 4
• Urgent CTA to characterize anatomy and plan repair 4
• Surgical repair within 24-48 hours to prevent free rupture 4

Critical Pitfalls

Do not delay emergency evaluation based on aneurysm size alone, as rapid growth rate is an independent high-risk feature that supersedes size thresholds for elective repair 4

Untreated symptomatic AAAs have a 79% one-year mortality rate with median survival of only 10.4 months, emphasizing the urgency of intervention 4

Female patients rupture at smaller mean diameters (5.0 cm vs 6.0 cm in men), requiring lower intervention thresholds 4, 6

Saccular aneurysms are more likely to rupture at smaller diameters than fusiform AAAs and warrant closer surveillance or earlier intervention 4