Arterial Aneurysms - Abdominal Aortic Aneurysms

Question 1

What is an abdominal aortic aneurysm?

Answer 1

Dilated abdominal aorta (increased circumference above 3cm).

Question 2

Why are AAAs associated with high mortality?

Answer 2

Rupture of AAA causes bleeding into the abdominal cavity and is often the first time the patient becomes aware of the aneurysm.

Question 3

What is the single most important risk factor for developing an AAA?

Answer 3

Atherosclerosis (so all associated risk factors of peripheral arterial disease).

Question 4

Screening of AAAs (3).

Answer 4

1. Commonest in elderly men - so perform an aortic US measurement in all men aged above 65.
2. Consider in women above age of 70 with existing risk factors.
3. Refer those with a large abdominal aorta to vascular surgery.

Question 5

Clinical Features of AAAs (2).

Answer 5

1. Asymptomatic until a complication e.g. rupture - retroperitoneal leak.
2. Non-Specific Abdominal Pain, Palpable Expansile Pulsation in Abdomen.

Question 6

Clinical Presentation of Ruptured AAA (5).

Answer 6

1. Severe Abdominal Pain that may radiate to the back/groin.
2. Haemodynamic Instability.
3. Pulsatile and Expansile Mass in Abdomen.
4. Collapse.
5. Loss of Consciousness.

Question 7

Commonest sites of AAAs (2).

Answer 7

1. Between renal and inferior mesenteric arteries.

2. 5% involve renal or visceral arteries.

Question 8

Pathophysiology of AAA (6).

Answer 8

1. Atherosclerosis.
2. Tunica Media of aorta gives vessel strength.
3. An enlarging atherosclerotic plaque causes pressure atrophy or Ischaemia atrophy of the tunica media and loss of elastic tissue.
4. Weakening of aortic wall - extracellular matrix is disrupted with a change in balance of Collagen and Elastin fibres.
5. Loss of Intima, Loss of Elastin Fibres from Media, Increased Proteolytic Activity and Lymphocyte Infiltration.
6. Dilation to form an aneurysm.

Question 9

Normal vs Abnormal Abdominal Aorta.

Answer 9

1. Normal Diameter of Infrarenal Aorta is 1.5cm in females and 1.7cm in males (after age of 50).
2. Diameters of above 3cm are considered aneurysmal.

Question 10

Rupture of AAAs (3).

Answer 10

1. 20% rupture anteriorly into peritoneal cavity - poor prognosis.
2. 80% rupture posteriorly into the retroperitoneal space.
3. Risk of rupture increases with diameter (5% for 5cm; 40% for 8cm) = Laplace’s Law (Radius increases, Tension Increases, Risk of Rupture).

Question 11

Investigations of AAAs (4).

Answer 11

1. Incidental Finding on AXR.
2. Diagnosis - US or CT/MR Angiography.
3. Normal <3cm, Small 3-4.4cm, Medium 4.5-5.4cm; Large - >5.5cm.
4. Do not investigate if ruptured.

Question 12

Management of Different Size AAAs.

Answer 12

Small - Rescan every 12 months.
Medium - Rescan every 3 months.
Large - Referral within 2 weeks to vascular surgery for probable intervention.

Question 13

DVLA and AAAs (3).

Answer 13

1. Inform DVLA if aneurysm is more than 6cm.
2. Stop driving if larger than 6.5cm.
3. Stricter with HGV licences.

Question 14

Complications of AAAs (2).

Answer 14

1. Rupture.

2. Thromboembolism (Stasis and Endothelial Injury).

Question 15

Emergency Management of Ruptured AAA (3).

Answer 15

1. Transfer directly to theatre from A&E Rhesus.
2. Do not investigate.
3. Permissive Hypotension (Aim for a lower-than-normal BP when performing fluid resuscitation since increasing BP can increase blood loss).

Question 16

Indications of AAAs Surgical Management (3).

Answer 16

1. Greater than 5.5cm.
2. Ruptured.
3. Diameter is growing by more than 1cm per year.

Question 17

Elective Surgical Repair of AAAs.

Answer 17

Insert artificial ‘graft’ into section of the aorta affected by aneurysm (Open repair via a laparotomy or endovascular aneurysm repair (EVAR).

Question 18

EVAR in AAAs (3).

Answer 18

1. Place stent into abdominal aorta via femoral artery.
2. Prevents blood from collecting in aneurysm.
3. Complication : Endo-Leak (where the stent fails to exclude blood from the aneurysm).