Abdominal Aortic Aneurysm

Question 1

Define

Answer 1

DEFINITION: a localised enlargement of the abdominal aorta such that the diameter is > 3 cm or > 50% larger than normal diameter.

NOTE: normal diameter of the aorta = 2 cm

True aneurysms are abnormal dilatations that involve all layers of the arterial wall

False aneurysms (pseudoaneurysm) involve a collection of blood in the outer layer only (adventitia) which communicates with the lumen (e.g. after trauma)

Question 2

Causes

Answer 2

degradation of the elastic lamellae
a leukocytic infiltrate - infections endocarditis + tertiary syphilis causing mycotic AAA
enhanced proteolysis
smooth muscle cell loss
connective tissue disorder 
atheroma 
inflammation trauma

Question 3

Risk factors

Answer 3

Severe atherosclerotic damage to aortic wall

Family history

Smoking

Male

Age

Hypertension

Hyperlipidaemia

Connective tissue disorders: Marfan’s syndrome, Ehlers-Danlos syndrome

Inflammatory disorders: Behcet’s disease, Takayasu’s arteritis

Question 4

Epidemiology

Answer 4

More common in MEN
Symptomatic AAA in men has an incidence of 25 per 100,000 at age 50, which increases markedly to 78 per 100,000 in those over the age of 70

Question 5

Symptoms

Answer 5

Unruptured:
Usually no symptoms
- Pain in back/abdomen/groin
- ±Limb ischemia due to distal embolism

Ruptured
Sudden and severe intermittent or continuous abdominal pain – radiates to back, iliac foassae or groin
- Cold, sweaty, faint, ±vomiting
- Collapse, syncope, shock

Question 6

Signs

Answer 6

• An expansile abdominal mass Expands and contracts
• ±Abdominal bruit
• Shock - tachycardia, pallor, hypotension

Question 7

Investigations

Answer 7

1. Abdominal ultrasound
2. ESR/ CRP - elevated - inflammatory AAA
3. FBC - leukocytosis and anaemia - infectious AAA
4. blood cultures - positive -
5. CT
6. MRI