Abdominal aortic aneurysm

Question 1

Define abdominal aortic aneurysm

Answer 1

a permanent pathological dilation of the aorta with a diameter >1.5 times the expected anteroposterior (AP) diameter of that segment

• given the patient’s sex and body size
• usually 3cm in size

Question 2

Below which arteries do 90% of aneurysms originate?

Answer 2

renal arteries (infra-renal)

Question 3

What are the risk factors of AAA?

Answer 3

• smoking
• family history
• increased age
• sex (male = incidence; female = rupture)
• congenital disorders e.g. bicuspid aortic valves (Aortic degeneration is accelerated)
• connective tissue disorders e.g. Marfan’s
• pregnancy (Aortic degeneration is accelerated)

Question 4

How does Marfan’s syndrome cause predisposition to AAA?

Answer 4

autosomal dominant anomaly in fibrillin type 1

–> cystic medial necrosis of the aorta

–> aorta = abnormal elasticity

–> progressive stiffening + dilation

Question 5

What is the epidemiology of AAA?

Answer 5

male prevalence = 4x female white smokers increasing age

Question 6

What are the presenting symptoms of an intact AAA?

Answer 6

most patients are asymptomatic; AAA is detected incidentally

uncommon:

• abdominal pain
• back pain
• groin pain

Question 7

What are the presenting symptoms of a ruptured AAA?

Answer 7

Triad of:

• abdominal and/or back pain
• pulsatile abdominal mass,
• hypotension

Question 8

What are the signs of an intact AAA on examination?

Answer 8

• usually asymptomatic
• pulsatile, expantile abdominal mass
• ~’trash feet’ - discolouration of toes 2° to emboli from aortic thrombus
• severely obese patients: unlikely for signs to be present (aorta is retroperitoneal)

Question 9

What are the primary investigations to be ordered if an AAA is suspected?

Answer 9

Abdominal US

Question 10

What are the secondary investigations to be considered if an AAA is suspected?

Answer 10

• ESR/CRP (–> inflammatory AAA)
• FBC (Leukocytosis + ~anaemia –> infectious AAA)
• blood cultures (+ ^^ –> infectious AAA)
• CT angiography (–> signs of rupture)
• MR(I) angiography (useful from pre-op strategy if patient has iodine contrast allergy)

Question 11

What

a) type of radiography is used to detect a ruptured AAA?
b) are the signs of a ruptured AAA?

Answer 11

a) CT angiography:

b)

• retroperitoneal haematoma
• discontinuity of aortic wall
• extravasation of contrast into peritoneal cavity