Abdominal Aortic Aneurysm (AAA)

Definition:
  • An abdominal aortic aneurysm (AAA) is a permanent pathological dilation of the abdominal aorta with a diameter over 1.5 times the expected anteroposterior diameter of that segment given the person’s sex and body size
    • Normally the diameter of the abdominal aorta ranges from 1.2ā€“2.4 cm
    • The threshold for diagnosis of AAA is an abdominal aortic diameter of 3.0 cm or greater
Epidemiology:
  • More common in males and those over the age of 65.
  • Associated with other vascular aneurysms, particularly popliteal artery aneurysms.
Risk Factors:
  • Smoking: Single most important risk factor.
  • Age
  • Family history of AAA
  • Hypertension
  • Hypercholesterolaemia
  • Atherosclerosis
Pathophysiology:
  • Debate on the exact cause but atherosclerosis is considered a major contributor.
  • Inflammatory processes weaken the aortic wall, leading to dilatation.
Clinical Features:
  • Most are asymptomatic and found incidentally on imaging or examination.
  • Symptoms, if present, include:
    • Abdominal pain or back pain.
    • Pulsatile mass in the abdomen.
  • If ruptured:
    • Severe abdominal pain
    • Shock
    • Collapse
Investigations:
  • Abdominal ultrasound: First-line investigation and used for screening.
  • CT angiography: Provides detailed imaging, particularly if surgery is being considered.
Management:
  • Small AAAs (<5.5cm in men, <5cm in women):
    • Managed conservatively with regular monitoring and ultrasound scans.
  • Larger or rapidly expanding AAAs:
    • May require surgical intervention either by open repair or endovascular aneurysm repair (EVAR).
  • Other management considerations:
    • Optimise blood pressure control.
    • Stop smoking.
    • Statins and aspirin if indicated.
Complications:
  • Rupture: Life-threatening emergency with high mortality.
  • Thrombosis or embolisation from the aneurysm.
Prognosis:
  • With early detection and appropriate management, prognosis can be good.
  • Ruptured AAA has a high mortality rate, with many patients dying before reaching the hospital.
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