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

Symptoms and Management of Abdominal Aortic Aneurysm (AAA)

Most abdominal aortic aneurysms (AAAs) are asymptomatic until they rupture, with the most common symptoms of rupture being abdominal or back pain, pulsatile abdominal mass, and hypotension. 1, 2

Symptoms of AAA

Asymptomatic Presentation

• Approximately two-thirds of AAAs are asymptomatic and often represent incidental findings on imaging studies 1
• Most AAAs are not detectable on physical examination, especially in obese patients 2, 3

Symptomatic Presentation

• Back, abdominal, or flank pain, sometimes radiating to the groin 1, 4
• Tenderness to palpation overlying the AAA 1
• Pulsatile abdominal mass (when large enough to be palpable) 2, 3
• Signs of embolism (e.g., blue toe syndrome) 1
• Compressive symptoms (e.g., obstructive uropathy) 1

Ruptured AAA (Surgical Emergency)

• Classic triad: abdominal/back pain, pulsatile abdominal mass, and hypotension 2
• Contained rupture may present with atypical low flank or abdominal pain 1
• Hypovolemic shock 5
• Mortality rate approaches 90% if rupture occurs outside the hospital 4

Diagnostic Approach

Screening Recommendations

• One-time ultrasound screening for men aged 65-75 who have ever smoked 1, 2
• Selective screening for men aged 65-75 who have never smoked 1, 2
• Targeted screening for first-degree relatives of patients with AAA 2

Imaging Modalities

1. Ultrasound (US)

   • Preferred method for screening and surveillance 1, 3
   • Should measure AP diameter in proximal, mid, and distal infrarenal aorta 1
   • Tends to underestimate size by approximately 4mm compared to CTA 1

2. CT/CTA

   • Gold standard for pre-intervention planning 1
   • Essential for evaluating juxtarenal or suprarenal aneurysms 1
   • Provides detailed information about aneurysm morphology 1

3. MRA

   • Alternative when CT cannot be performed (e.g., contrast allergy) 1
   • Not suitable for patients with severe renal insufficiency unless non-contrast protocols are available 1

Management of AAA

Surveillance Recommendations

Based on aneurysm size 1, 2:

• 25-29 mm: Every 4 years
• 30-39 mm: Every 3 years
• 40-44 mm: Every 12 months
• 45-49 mm (men)/40-45 mm (women): Every 12 months
• 50-55 mm (men)/45-50 mm (women): Every 6 months

Medical Management

• Aggressive blood pressure control (target SBP 120-129 mmHg if tolerated) 2
• Lipid management (LDL-C <1.4 mmol/L or 55 mg/dL) 2
• Smoking cessation (essential to reduce growth rate) 1, 2, 3
• Beta-blockers may be considered to reduce aneurysm expansion rate 2

Indications for Intervention

1. Size-based criteria:

   • ≥5.5 cm in men 1, 2
   • ≥5.0 cm in women 2
   • Rapid growth (≥5 mm in 6 months or ≥10 mm in 12 months) 1

2. Symptom-based criteria:

   • Any symptomatic AAA regardless of size 2, 4
   • Pain attributable to the AAA 1

3. Morphology-based criteria:

   • Saccular aneurysms (may warrant intervention at smaller sizes) 1, 2

Intervention Options

1. Endovascular Aneurysm Repair (EVAR):

   • Preferred when anatomically suitable 2
   • Lower perioperative mortality and morbidity compared to open repair 2
   • Requires lifelong surveillance imaging 2

2. Open Surgical Repair:

   • Indicated when endovascular repair is not anatomically suitable 2
   • May be preferred for younger, lower-risk patients 2
   • Less intensive follow-up required compared to EVAR 2

Post-Intervention Surveillance

• After EVAR: Initial imaging at 1 month and 12 months, then annually for at least 5 years 2
• After open repair: Less intensive follow-up but still requires periodic assessment 2

Common Pitfalls and Caveats

• Underestimating rupture risk in women, who may rupture at smaller diameters than men 1, 2
• Assuming thrombus reduces rupture risk (evidence shows it does not reduce pressure on the aneurysm wall) 2
• Relying solely on physical examination for diagnosis (most AAAs are not palpable) 2
• Delaying intervention for symptomatic aneurysms (should be repaired within 24-48 hours) 1
• Inadequate surveillance leading to unexpected rupture 2
• Failing to recognize that small aneurysms can occasionally rupture (though rare) 6

By following these evidence-based guidelines for diagnosis and management, clinicians can effectively identify and treat AAAs to reduce the risk of rupture and associated mortality.