Vascular

Question 1

AAA causes

Answer 1

Cause

•atherosclerosis

• 90%of cases
• action of matrix metalloproteinases in degradation of extracellular matrix important

•connective tissue disorders

• 5% of cases
• Marfan’s syndrome
• Ehler Danlos syndrome

•inflammatory

• < 5%
• younger age group
• marked thickening of aneurysm wall
• fibrosis of adjacent retroperitoneum
• adherence of adjacent structures to anterior aneurysm wall

•mycotic

• < 1% of all aortic aneurysms
• atypical location
• younger age group
• usually saccular
• common causative organisms are Salmonella and Staph aureus

Question 2

Bedside US in AAA

Answer 2

Ultrasound

• reliable in diagnosis of the presence of an aneurysm
• portable to resuscitation room
• AP diameter size more important than transverse diameter
• accurate in the hands of emergency physicians
• 90 - 100% sensitive for aneurysms > 3 cm
• > 95% specific

•features of rupture

• seen in left posterior wall in 67% involves inferior portion in 61%
• retroperitoneal haematoma (echogenic retroperitoneal fluid collection)
• hypoechoic areas within the thrombus
• abrupt interruption of the thrombus
• floating thrombus
• break in the aortic wall

•limitations

• adequate quality images may not be able to obtained in approximately 10% of patients
• usually due to overlying bowel gas
• a left lateral approach may allow aortic visualisation
• can’t reliably diagnose rupture
• aneurysm may be incidental finding and not the cause of the patient’s symptoms
• difficult to assess branch involvement