Abdominal Aortic Aneurysm

Question 1

What is an aneurysm?

Answer 1

• True aneurysm - segmental, full-thickness (all three layers) dilation of a blood vessel that is 50 percent greater than the normal aortic diameter. In most adults, an aortic diameter >3.0 cm is generally considered aneurysmal.
• • False aneurysms - bound only by the tunica adventitia. Are much less common and are usually due to a traumatic or infectious etiology.

Question 2

How can you define an aneurysm?

Answer 2

• Site
• Size
• Shape
• True or false
• Aetiology
• Congenital or acquired

Question 3

What are the risk factors for AAA?

Answer 3

• Older age
• Male sex
• Cigarette smoking
• Positive family history of AAA
• Other large artery aneurysms (eg, iliac, femoral, popliteal)
• Atherosclerosis
• Hypertension

Question 4

What is the pathophysiology of AAA?

Answer 4

Multifactorial - Alterations in vascular wall biology leading to a loss of vascular structural proteins and wall strength

• Inflammation (eg tobacco) encourages smooth muscle apoptosis
• Extracellular matrix degradation - metalloproteinases (MMPs) and elastases
• Haemodynamic pressures upregulate degradation proteins
• Atherosclerosis/stenosis causes flow-related shear stress

Question 5

What are the risk factors for rupture of AAA?

Answer 5

• Large initial aneurysm diameter (>5.5 cm)
• Current smoking
• Elevated blood pressure
• Greater aortic expansion rate (>0.5 cm/year)
• Female sex
• Symptoms

Question 6

What are the symptoms of AAA?

Answer 6

• Asymptomatic AAA - found incidentally or via screening
• Symptomatic (nonruptured) AAA - abdominal pain, unexplained thrombus/embolisation/limb ischaemia, fever/weightloss (infective), sudden hernia (increased abdo pressure), heart failure (fistula), disseminated intravascular coagulation
• Ruptured AAA — sudden death, shock (acute blood loss), pain

Question 7

What are the signs of AAA?

Answer 7

• Sinus tachycardia
• Moderate-to-severe hypotension
• Pulsatile mass
• Bruits
• Grey Turner sign
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Question 8

How would you investigate a symptomatic AAA?

Answer 8

Risk factors, examination, radiology

Imaging asymptomatic patients — USS

Imaging symptomatic patients - Stable -USS, unstable - CT

Question 9

What CT scan findings are in keeping with a ruptured AAA?

Answer 9

Retroperitoneal hematoma

Indistinct aortic wall

Retroperitoneal stranding

Loss of the fat plane between the aorta and surrounding tissue

Extravasation of intravenous contrast outside the aorta