Abdominal Aortic Aneurysm: Symptoms, Causes & Treatment

An abdominal aortic aneurysm (AAA) is a permanent focal dilation of the abdominal aorta exceeding 3 cm in diameter or ≥150% of the normal aortic diameter. AAA predominantly affects men over 60 and is strongly associated with cigarette smoking (the dominant risk factor), hypertension, hyperlipidemia, and atherosclerosis. Prevalence in Western populations is 3–9% in men over 60; 1–2% in women. The aorta is most commonly affected infrarenally (below the renal arteries) in 95% of cases.

AAA expansion is typically silent — most patients are asymptomatic and discovered only on imaging for unrelated conditions or during screening. Mean expansion rate is 2–3 mm/year for small aneurysms, accelerating with size; aneurysms >5.5 cm expand fastest and carry the highest rupture risk. Rupture is catastrophic: blood floods the retroperitoneum or peritoneal cavity; pre-hospital mortality exceeds 80%. Even in-hospital mortality of ruptured AAA is 40–60%. By contrast, elective repair of large unruptured AAA carries <5% operative mortality at experienced centers.

The dramatic difference in outcomes between ruptured and elective repair drives the rationale for surveillance and timely elective surgery. US Preventive Services Task Force (USPSTF) recommends one-time abdominal ultrasound screening for men aged 65–75 who have ever smoked (≥100 lifetime cigarettes). UK NHS offers similar AAA screening at age 65 for men.

• Most AAAs are asymptomatic — discovered incidentally on imaging (CT, ultrasound) or at screening
• Vague abdominal, back, or flank discomfort from large aneurysm pressing on adjacent structures
• Visible or palpable pulsatile abdominal mass in thin individuals (unreliable sign)
• Symptomatic unruptured AAA: new onset back/abdominal pain signals rapid expansion or impending rupture — treat as emergency
• Ruptured AAA: sudden severe tearing abdominal or back pain + hemodynamic collapse (hypotension, pallor, tachycardia) = catastrophic emergency with minutes to hours to death without surgery

• Cigarette smoking: the strongest modifiable risk factor — increases AAA risk 3–5 fold; current smokers have ~8× risk of non-smokers
• Atherosclerosis: aortic wall degeneration with loss of elastin and smooth muscle
• Hypertension: increases wall stress (LaPlace's law) accelerating expansion
• Positive family history: first-degree relative with AAA increases risk 4-fold
• Male sex: 6× higher risk than women; women develop AAA at older age but with worse outcomes after rupture
• Connective tissue diseases: Marfan syndrome, Ehlers-Danlos type IV (connective tissue weakness)

Abdominal ultrasound: gold standard for screening and size surveillance — non-invasive, no radiation, accurate diameter measurement. CT angiography (CTA): definitive pre-operative planning — characterizes aneurysm morphology, neck length and angulation, renal artery involvement, iliac extension, thrombus, and access vessels for EVAR planning. In suspected ruptured AAA with hemodynamic instability: do not delay for CT — proceed directly to operating room. In stable suspected rupture: emergent CTA. MRI: alternative to CT when contrast contraindicated.

Surveillance: small AAA (men <5.5 cm, women <5.0 cm) — interval ultrasound monitoring every 6–12 months for 4–5.4 cm, annually for <4 cm. Elective repair: indicated when AAA ≥5.5 cm in men (≥5.0 cm in women), rapid expansion (>1 cm/year or >0.5 cm/6 months), or symptomatic. Endovascular aneurysm repair (EVAR): catheter-delivered stent-graft; minimally invasive; preferred when anatomy suitable (infrarenal neck length ≥1.5 cm, adequate access vessels) — lower 30-day mortality but higher late reintervention rate than open surgery. Open surgical repair: direct aortic reconstruction; preferred for younger fit patients and unfavorable anatomy for EVAR. Ruptured AAA: immediate emergency surgery (EVAR or open); activate massive transfusion protocol; permissive hypotension until aortic control achieved.

• Rupture: catastrophic retroperitoneal or intraperitoneal hemorrhage — 80%+ mortality without immediate surgery
• Distal embolization from mural thrombus: blue toe syndrome, mesenteric or renal ischemia
• Post-repair: spinal cord ischemia (paraplegia — especially with juxtarenal repair), graft infection, endoleak (EVAR-specific), renal failure

• Smoking cessation: the single most important intervention — reduces expansion rate and rupture risk
• Blood pressure control (target <130/80 mmHg); antiplatelet and statin therapy for cardiovascular risk reduction
• Screening: one-time abdominal ultrasound for men 65–75 who have ever smoked (USPSTF Grade B)
• Family screening: first-degree male relatives of AAA patients should be screened from age 60