Introduction

Prevalence of abdominal aortic aneurysm (AAA) is 3% in those >50 years. The frequency increases steadily in men >55 yrs, reaching a peak of 5.9% at 80–85 yrs. In women, the peak is 4.5% at age > 90 years. Male: female ratio is 4:1. Abdominal aortic aneurysms are 3–7 times more common than thoracic aneurysms. Other aneurysms coexisting with abdominal are iliac (20–30%) and femoropopliteal (15%). Popliteal aneurysms are a marker of AAA. AAAs are present in 8% of patients with unilateral and in 50% with bilateral popliteal aneurysms. Cigarette smoking is associated with an increased incidence of AAA, 8:1 as compared with non-smokers. Popliteal aneurysms are the most common peripheral arterial aneurysms. Atherosclerotic in 95%, M:F 30:1, sixth to seventh decade, bilateral in 50%. Rare causes are entrapment syndrome or trauma.

Definition

An aneurysm is a permanent localized dilation of an artery with an increase in diameter of greater than 50% (1.5 times) its normal diameter. Ectasia refers to dilation of an artery that does not reach the above threshold.

Classification

True (contains all components of the arterial wall – intima, media and adventitia) or false (only adventitia). Congenital or acquired (atherosclerosis, trauma, infection, or medial cystic necrosis). Saccular (arising from one part of the arterial wall) or fusiform (generalized dilation of the arterial wall) (Figures 103 and 104). The aneurysms can also be divided into: aneurysms of the aortoiliac area, peripheral aneurysms and splanchnic aneurysms. They may present electively or in an emergency.