Abdominal Aortic Aneurysm

Overview

The aorta is the largest blood vessel in the human body, carrying oxygen-rich blood from the heart to the rest of the body. An abdominal aortic aneurysm occurs when a section of the aorta below the diaphragm weakens and bulges outward, forming a balloon-like sac. This weakening typically develops in the infrarenal region, below where the renal arteries branch off to supply the kidneys.

AAAs are classified by size: small (3.0-4.4 cm), medium (4.5-5.4 cm), and large (≥5.5 cm). The normal diameter of the abdominal aorta is approximately 2.0 cm, so an aneurysm represents a 50% or greater increase in diameter. The risk of rupture increases exponentially with size, making monitoring and timely intervention critical. Approximately 200,000 people in the United States are diagnosed with AAA annually, and ruptured AAAs cause about 15,000 deaths each year.

The condition predominantly affects older adults, particularly men over 65 who have a history of smoking. The mortality rate from a ruptured AAA is extremely high, with only about 20% of patients surviving even with emergency treatment. However, when detected early and managed appropriately, the prognosis is excellent, with elective repair having a success rate of over 95%.

Symptoms

Most abdominal aortic aneurysms develop silently without causing symptoms until they become large or rupture. This asymptomatic nature makes AAAs particularly dangerous, as many people are unaware they have the condition until a life-threatening event occurs.

Common Symptoms of Intact AAA

• Back pain - often described as deep, constant pain in the lower back
• Burning abdominal pain - persistent discomfort in the abdomen
• Pulsating sensation near the navel - feeling of heartbeat in the abdomen
• Feeling of fullness after eating small amounts
• Nausea or vomiting from compression of nearby structures

Symptoms of Expanding or Leaking AAA

• Sharp abdominal pain - sudden, severe pain indicating expansion
• Pain radiating to the back, groin, buttocks, or legs
• Palpitations - awareness of rapid or irregular heartbeat
• Clammy, sweaty skin
• Rapid pulse rate
• Feeling of impending doom

Emergency Symptoms of Ruptured AAA

• Sudden, intense abdominal or back pain (often described as "tearing" or "ripping")
• Shortness of breath - from blood loss and shock
• Lightheadedness or loss of consciousness
• Rapid, weak pulse
• Cold, clammy skin with profuse sweating
• Confusion or altered mental state
• Blue discoloration of skin (cyanosis)

Complications-Related Symptoms

• Arm swelling - rare, may indicate compression of venous return
• Leg pain or numbness from decreased blood flow
• Erectile dysfunction in men from compromised pelvic blood flow
• Blood clots causing embolic symptoms

Causes

The development of abdominal aortic aneurysms is multifactorial, involving a complex interplay of genetic predisposition, environmental factors, and degenerative processes that weaken the aortic wall. Understanding these causes helps identify at-risk individuals and implement preventive strategies.

Atherosclerosis

The primary cause of AAA is atherosclerosis, a condition where fatty deposits (plaques) build up in arterial walls. This process:

• Weakens the aortic wall by damaging elastic fibers
• Causes chronic inflammation that degrades structural proteins
• Reduces blood flow to the aortic wall itself
• Creates areas of weakness prone to dilation

Genetic and Familial Factors

• Family history: 15-20% of AAA patients have a first-degree relative with the condition
• Genetic syndromes: Marfan syndrome, Ehlers-Danlos syndrome type IV
• Genetic variations: Polymorphisms affecting elastin and collagen production
• Male predominance: Suggests X-linked or hormonal factors

Inflammatory and Infectious Causes

• Vasculitis: Takayasu arteritis, giant cell arteritis
• Infectious aortitis: Syphilis, salmonella, tuberculosis (rare)
• Inflammatory AAA: Characterized by thick inflammatory tissue
• Autoimmune processes: Contributing to wall degradation

Biomechanical Factors

• High blood pressure increasing wall stress
• Turbulent blood flow patterns
• Loss of elastin and collagen with aging
• Proteolytic enzyme imbalance

Risk Factors

Several factors significantly increase the risk of developing an abdominal aortic aneurysm. Understanding these risks helps identify candidates for screening and preventive measures.

Major Risk Factors

• Smoking: The most important modifiable risk factor
  • Increases risk 3-5 fold
  • Duration and intensity correlate with risk
  • Former smokers remain at elevated risk
• Age: Risk increases significantly after age 65
• Male gender: Men are 4-6 times more likely to develop AAA
• Family history: First-degree relatives have 20% risk

Cardiovascular Risk Factors

• Hypertension - especially uncontrolled
• Atherosclerosis in other vessels
• High cholesterol levels
• Coronary artery disease
• Peripheral artery disease

Other Contributing Factors

• Ethnicity: Higher in Caucasians than African Americans or Asians
• Height: Taller individuals at increased risk
• COPD: Associated with increased AAA risk
• Previous aneurysms: In other locations

Protective Factors

• Female gender (estrogen may be protective)
• Diabetes mellitus (paradoxically protective)
• African American ethnicity
• Regular physical activity

Diagnosis

Early detection of abdominal aortic aneurysms is crucial for preventing rupture. Most AAAs are discovered incidentally during imaging for other conditions or through targeted screening programs for at-risk populations.

Physical Examination

Physical findings may include:

• Palpable pulsatile mass: Felt above the umbilicus
• Abdominal bruit: Audible turbulent blood flow
• Sensitivity: Only 30-40% for detecting AAA
• Limitations: Difficult in obese patients

Imaging Studies

Ultrasound (Primary Screening Tool)

• Nearly 100% sensitive and specific for AAA detection
• Non-invasive, no radiation exposure
• Can measure aneurysm diameter accurately
• Limited by bowel gas and obesity

CT Angiography (Gold Standard)

• Provides detailed anatomy for surgical planning
• Evaluates extent, shape, and relationship to branch vessels
• Can detect rupture or impending rupture
• Requires contrast and radiation exposure

MRI/MRA

• Alternative when CT contrast is contraindicated
• Excellent soft tissue visualization
• No radiation exposure
• Time-consuming and expensive

Screening Recommendations

• USPSTF Guidelines: One-time ultrasound screening for men aged 65-75 who have ever smoked
• Consider screening: Men 65-75 who never smoked, women 65-75 who smoked or have family history
• Family history: Screen at age 65 or 10 years before youngest affected relative
• Follow-up: Based on initial aneurysm size

Treatment Options

Treatment of abdominal aortic aneurysms depends on the size, growth rate, location, and patient's overall health. The goal is to prevent rupture while minimizing procedural risks. Management strategies range from watchful waiting to emergency surgery.

Surveillance (Small Aneurysms <5.5 cm)

Most small AAAs are managed conservatively with regular monitoring:

• 3.0-3.9 cm: Ultrasound every 2-3 years
• 4.0-4.9 cm: Ultrasound every 6-12 months
• 5.0-5.4 cm: Ultrasound every 3-6 months or consider repair
• Growth >0.5 cm/year: Consider earlier intervention

Medical Management

• Smoking cessation: Critical to slow growth and reduce rupture risk
• Blood pressure control: Target <130/80 mmHg with beta-blockers preferred
• Statin therapy: May slow aneurysm growth
• Antiplatelet therapy: For cardiovascular protection
• Exercise restrictions: Avoid heavy lifting and straining

Surgical Repair Indications

• Aneurysm diameter ≥5.5 cm in men, ≥5.0 cm in women
• Rapid growth (>0.5 cm in 6 months)
• Symptomatic aneurysm regardless of size
• Saccular or eccentric morphology
• Patient preference with acceptable surgical risk

Endovascular Aneurysm Repair (EVAR)

Minimally invasive approach using stent grafts:

• Advantages:
  • Lower perioperative mortality (1-2%)
  • Shorter hospital stay (1-3 days)
  • Faster recovery time
  • Less invasive procedure
• Disadvantages:
  • Requires lifelong surveillance
  • Higher reintervention rate
  • Not suitable for all anatomies
  • Endoleak complications

Open Surgical Repair

Traditional approach with direct aneurysm replacement:

• Advantages:
  • Durable, definitive repair
  • No need for frequent follow-up imaging
  • Lower long-term reintervention rate
  • Suitable for complex anatomy
• Disadvantages:
  • Higher perioperative mortality (3-5%)
  • Longer hospital stay (5-10 days)
  • Longer recovery (6-12 weeks)
  • Major abdominal surgery risks

Emergency Treatment for Rupture

• Immediate surgical intervention required
• Massive blood transfusion protocols
• Permissive hypotension until surgical control
• EVAR preferred if anatomy suitable and expertise available
• Mortality remains 40-50% even with treatment

Prevention

While some risk factors for AAA like age and genetics cannot be modified, many preventive measures can significantly reduce the risk of developing or progression of an aneurysm.

Primary Prevention

• Never start smoking: Most effective prevention strategy
• Maintain healthy blood pressure: Regular monitoring and treatment
• Cholesterol management: Diet and statins as indicated
• Regular exercise: Moderate aerobic activity
• Healthy diet: Mediterranean diet may be protective
• Weight management: Maintain healthy BMI

Secondary Prevention (Existing AAA)

• Smoking cessation programs: Counseling and pharmacotherapy
• Regular surveillance: Adherence to monitoring schedule
• Activity modification: Avoid heavy lifting, straining
• Blood pressure control: Beta-blockers may slow growth
• Treat infections promptly: To avoid inflammatory stress

Screening as Prevention

• Participate in recommended screening programs
• Know your family history
• Discuss screening with doctor if risk factors present
• Consider screening for other aneurysms if AAA found

When to See a Doctor

Call 911 immediately for:

• Sudden, severe abdominal or back pain
• Pain described as "tearing" or "ripping"
• Signs of shock: rapid pulse, clammy skin, confusion
• Fainting or loss of consciousness
• Severe shortness of breath with abdominal pain

Schedule urgent appointment for:

• New or worsening back pain in someone over 60
• Pulsating sensation in abdomen
• Persistent burning abdominal pain
• Family history of AAA and reaching age 65

Routine screening indicated for:

• Men 65-75 who have ever smoked
• Men or women over 65 with family history of AAA
• Anyone with peripheral artery disease
• Follow-up for known small aneurysm

Related Conditions

• Thoracic Aortic Aneurysm
• Aortic Dissection
• Peripheral Artery Disease
• Atherosclerosis
• Hypertension
• Marfan Syndrome

References

1. Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2-77.
2. US Preventive Services Task Force. Screening for Abdominal Aortic Aneurysm: US Preventive Services Task Force Recommendation Statement. JAMA. 2019;322(22):2211-2218.
3. Wanhainen A, Verzini F, Van Herzeele I, et al. Editor's Choice - European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the Management of Abdominal Aorto-iliac Artery Aneurysms. Eur J Vasc Endovasc Surg. 2019;57(1):8-93.
4. Kent KC. Clinical practice. Abdominal aortic aneurysms. N Engl J Med. 2014;371(22):2101-2108.
5. Golledge J. Abdominal aortic aneurysm: update on pathogenesis and medical treatments. Nat Rev Cardiol. 2019;16(4):225-242.