AAA

Question 1

What is AAA?

Answer 1

A permament and irreversible localised dilatation of the abdominal aorta by more than 50% of its normal diameter.

Question 2

What size is it normally? And what does it increase to?

Answer 2

The abdominal aorta is normally 2cm so an AAA is classed as >3cm.

Question 3

Where (else) can aortic aneurysms occur?

Answer 3

Majority of aortic aneurysms are abdominal but some can be thoracic and can also extend to affect the iliac, femoral and popliteal arteries

Question 4

Where do 90% of AAA occur?

Answer 4

Infrarenally - below level of kidneys

Question 5

What different types of aneurysm can you have?

Answer 5

fusiform (most AAAs) or sac-like (e.g. Berry aneurysms).

Question 6

What is a true aneurysm?

Answer 6

A true aneurysm involves all layers of the arterial wall.

Question 7

What is false aneurysm?

Answer 7

False aneurysms (pseudoaneurysms) involve a collection of blood in the outer layer only (adventitia) which communicates with the lumen.

Question 8

What does incidence increase with?

Answer 8

Incidence increases with age.

Question 9

How common is?

Answer 9

Present in 3% of population >50y

Question 10

More in male or female?

Answer 10

M 3x>F and in 1/4 of male children of an affected individual

Question 11

What ethnicity is more common in?

Answer 11

Rarely affects African/Hispanic, low prevalence in Asians, mainly affects Caucasians

Question 12

Who is it most common in?

Answer 12

8:1 smokers

Question 13

Who is it less common in?

Answer 13

Less common in diabetics

Question 14

Aetiology

Answer 14

• Atherosclerosis - new evidence suggests this is not the only factor and that there is also a distinct arterial pathology
• Trauma
• Infection e.g. mycotic aneurysm in endocarditis, tertiary syphilis
• Connective tissue disorders (e.g. Marfan’s, Ehlers-Danlos)
• Inflammatory e.g. Takayasu’s aortitis

Question 15

What is the pathophysiology?

Answer 15

AAA results from a failure of the major structural proteins of the aorta – elastin and collagen. The mechanism is not fully understood but it is to do with proteolysis or degradation of the proteins. The elimination of elastin from the tunica media means the aortic wall is more susceptible to the influence of blood pressure. The diameter of the aorta gradually decreases distally and infrarenally it contains less elastin which means the mechanical tension is higher. This is why abdominal aneurysms are more common than thoracic.

Question 16

What are the risk factors?

Answer 16

•	Smoking – 8x more likely
•	Male
•	Family history – 15% of first degree releatives will also develop an AAA; probably strong genetic links
•	Age
•	HTN
•	Hyperlipidaemia
•	COPD
DM seems to decrease the risk

Question 17

What are the symptoms?

Answer 17

• Most are asymptomatic and found on routine abdo exam
• As it expands it may cause:
• Epigastric pain radiating to back
• Pulsating sensations in abdomen
• Pain in chest, lower back or scrotum – due to pressure on nearby structures; back pain may be due to erosion of vertebral bodies

Question 18

What are the signs?

Answer 18

•	Pulsatile abdominal swelling
•	Aortic bruits
Ruptured AAA may present with:
•	Pain in abdomen, back or loin – may be sudden and severe
•	Hypotension
•	Pulsatile and expansile abdominal mass
•	Syncope, shock or collapse
Sudden death

Question 19

What investigations?

Answer 19

Blood tests
ECG
Imaging – USS/ CT/ MRI angiography

Question 20

What would you look for on blood tests?

Answer 20

• FBC, clotting, renal function, liver function
• Cross-match if surgery planned
• ESR/CRP if inflammatory cause suspected

Question 21

What do you see on USS/ CT/ MRI angiography?

Answer 21

1.	USS
•	Used for initial assessment and follow-up
•	Can assess to accuracy of 3mm
2.	CT
•	Assesses in more anatomical detail
•	If with contrast then can show rupture
3.	MRI angiography
Put in two cannulas; call a vascular surgeon and anaesthetist; treat with ORh –ve blood; keep systolic BP <100mmHg; take blood for amylase, Hb, crossmatch

Question 22

What conservative management?

Answer 22

• For asymptomatic AAAs where risk of repair is higher than risk of not treating
• Modify and treat risk factors
• Treat underlying causes e.g. infection
• Regular monitoring
• DVLA must be notified of aneurysms >6cm. >6.5cm disqualifies person from driving.

Question 23

What medical treatments?

Answer 23

• To treat risk factors and underlying causes
• Some evidence that some drugs may reduce diameter of small aneurysms e.g. doxycycline, roxithromycin, ACE-I, losartan, statins, low-dose aspirin

Question 24

What surgical managements?

Answer 24

• Indicated for all aneurysms >5.5cm, rupture, rapid expansion or onset of sinister symptoms
Open repair. EVAR (Endovascular aneurysm repair)
• Stent-graft system through femoral arteries
Less invasive but failure of graft can occur

Question 25

What differentials?

Answer 25

Acute abdomen e.g. cholecystitis, appendicitis, bowel obstruction, pancreatitis, pyelonephritis. If TAA then other causes of chest pain e.g. MI, PE

Question 26

What is the prognosis?

Answer 26

Overall mortality for elective surgery repair is 2.4%.
Increasing size = increasing risk of rupture.
1 in 3 patients with rupture reach hospital alive and 20% of those that do don’t reach theatre.

Question 27

What are the complications?

Answer 27

Aortic dissection
Rupture
Ureterohydronephrosis – due to compression of the ureters
Distal embolization leading to limb ischaemia – mirco-embolic lower limb infarcts with palpable pedal pulses suggest popliteal or abdominal aneurysm
Retroperitoneal fibrosis or inflammation

Question 28

How do you manage aortic dissection?

Answer 28

• Tear in inner wall of aorta allows blood to flow between layers of aorta forcing the layers apart
• Severe characteristic chest/abdominal pain (depending on location of dissection described as ‘tearing’)
• Type A (70%) in ascending aorta and Type B elsewhere
• Associated with other symptoms of decreased blood supply to organs
• Medical emergency – can lead to aortic rupture and death
• Usually in patients with hypertension, aortic aneurysm or disorders which affect blood vessel wall integrity
• Diagnosis made using medical imaging
• Surgery is used to treat Type A dissections
• Emergency blood pressure lowering medication given for descending/abdominal aorta dissections