Abdominal Aortic Aneurysm

Question 1

Define aneurysm

Answer 1

Permanent localised dilatation of artery with increase in diameter more than 1,5 times the expected size or adjacent normal artery. 3 cm for AAA

Question 2

Define arteriomegaly

Answer 2

Diffuse arterial enlargement with an increase in diameter more than 50% above normal or expected

Question 3

Define ectasia

Answer 3

Permanent localized dilatation of an artery <50% of normal diameter

Question 4

Define pseudo aneurysm

Answer 4

Contained extravasated blood from a disruption in the arterial wall, doesn’t contain all 3 layers of the vessel.

Question 5

Name and describe 2 morphological types of aneurysms

Answer 5

• Saccular: only part of the vessel circumference
• fusiform: entire circumference

Question 6

Name 7 causes aneurysm.

Answer 6

• Degenerative (used to be called atherosclerotic): most common
• Infection: HIV, bacterial eg S aureus, syphilis
• pseudo-aneurysm: trauma and anastomotic breakdown
• connective tissue disorders: marfan, ehlers-danlos syndrome
• inflammation: Takayasu’s disease
• post stenotic: thoracic outlet obstruction, coarctation
• aortic dissection
• intimal medial mucoid degeneration

Question 7

Name 6 risk factors degenerative aneurysms

Answer 7

Host
• Male
• Caucasian
• family history, especially if the relative is female

Lifestyle
• smoking

Medical conditions
•Hypertension
• hypercholesterolaemia

Question 8

Pathogenesis aneurysms? (4)

Answer 8

Multifactorial:
• proteolytic degradation of aortic wall connective tissue (elastin and collagen through matrix metalloproteinase mmp)
• inflammation and immune response: macrophages and neutrophils → cytokine release → protease activation
• biochemical wall stress (berry aneurysms more common in infra-renal segment because less elastin (dilatation) and collagen (rupture))
• molecular genetics: less type 3 collagen

Question 9

Symptoms AAA? (10)

Answer 9

• 75% asymptomatic!
• Local compression:
- d3 d4 duodenal compression → early satiety, nausea, vomiting
- left ureter compression → obstructive uropathy, recurrent UTI
- erode vertebral bodies → back pain
• Acute rupture 20%, triad in 50%:
- acute abdominal pain
- haemodynamic instability
-Pulsatile abdominal mass
• emboli
- distal macroembolism → acutely threatened limb
- distal microembolism → blue toe syndrome
• fistula (rare): aorto-duodenal, aorto-caval

Question 10

Clinical examination AAA? (4)

Answer 10

• bimanual abdominal palpation
• size. Expands laterally
• bruit on auscultation
• palpable thrill

Question 11

Investigations for AAA? (3)

Answer 11

• Duplex ultrasound: first line to confirm clinically suspected AAA, and best for screening and surveillance
• multidetector CTA: most accurate to get details.. Demonstrates extent, calibre, size, degree of calcification, neck characteristics, mural thrombus presence, vascular anomalies eg horseshoe kidney, relationship to renal arteries and left renal vein.
• MRA: similar results CT, only do if kidney failure so can’t handle contrast, pregnant ( less radiation) or risk distal embolisation.

Catheter directed angiography reserved for endovascular procedures

Question 12

Name 4 reasons that screening for AAA is important, and how and when to do it

Answer 12

From age 65 with duplex ultrasound
• most AAA asymptomatic
• primary aim in managing AAA is to prevent rupture
• morbidity and mortality of repair of ruptured AAA is 50-70 % compared to 1-5% for elective repair
• patients who survive repair have similar life expectancy as general population

Question 13

Indications to repair AAA? ( 5)

Answer 13

If risk of rupture outweigh operative risk! These risks include:
• size: male 5,5 cm, 5,0 cm female
• expansion rate > 1cm/year (0,5cm/6 months)
• factors associated with increased expansion rate: smoking, COPD
• symptomatic eg compression, embolism, fistula

Question 14

Preoperative assessment of elective AAA repair? (3)

Answer 14

• ECG and echo (cardiac function )
• 24 hour creatinine clearance (renal function)
• lung function tests.
Patients must be fit for open surgery, high risk can be offered endovascalar EVAR if meet requirements

Question 15

Management AAA? (5)

Answer 15

Non-operative: prevent small aneurysms from enlarging or decrease expansion rate of large
• Best medical therapy: ace-inhibitors, statins, aspirin, stop smoking, exercise, control diabetes
. Best medical therapy must reduce rate of expansion by > 50% to keep a 4.0cm aneurysm from reaching the 5.5cm threshold within 5 years.
• ultrasound surveillance
- 3 monthly for 4.5-5,5cm
-6 monthly for 3-4.5 cm
• no benefit in early surgery over surveillance for small aneurysms

Only operate when meet 1 or more of the 3 risks of rupture. Options include open surgery or evar

Question 16

How is elective open repair of AAA done?

Answer 16

Transperitoneal (preferred) or retroperitoneal.

Question 17

Name 5 indications for retroperitoneal instead of transperitoneal elective open repair of AAA

Answer 17

• Hostile abdomen: urinary or enteric stoma, previous abdominal or pelvic irradiation, ascites, morbid obesity, prior abdominal surgery.
• inflammatory aneurysms
• aneurysms associated with horseshoe kidneys
• suprarenal aneurysms
• renal ectopy

Question 18

Name 6 early complications of elective open repair of AAA

Answer 18

• Cardiorespiratory failure
• Haemorrhage
• renal failure
• limb ischaemia
• colonic ischaemia
• venous thromboembolism

Question 19

Name 3 late complications of elective open repair of AAA

Answer 19

• Graft sepsis
•Pseudo aneurysms
• aorto-enteric fistula

Question 20

How is endovascular AAA repair (evar) done?

Answer 20

Exclusion of AAA from ischaemic circulation by means of pre-op sized deployment stent graft, preventing further aneurysm expansion and elimination of rupture risk
Lower mortality than open but less durable

Question 21

Name 6 patient selection requirements for endovascular AAA repair (evar)

Answer 21

Aneurysm neck morphology
• straight neck, minimal length of 1 cm
• minimum of 15 mm for 60° angulation
• max diameter 3cm
Funnel shaped neck, thrombus extending to neck, excessive calcifications = contraindications!

Iliac vessels
• iliac arteries of sufficient calibre > 7 mm to tolerate passage of graft

Aortic bifurcation
• diameter must be wide enough to accept both graft limbs without their compressing each other (2cm)

Question 22

Name 8 complications EVAR

Answer 22

• iatrogenic vessel injury
• endoleak: arterial flow of blood into excluded aneurysm sac but outside lumen of the deployed stent graft
• embolisation
• graft migration, dislocation and displacement
• post-implant syndrome: early back pain and fever without leucocytosis
• contrast nephropathy
• graft sepsis
• Graft limb thrombosis

Question 23

How often should post-op surveillance for complications be performed after AAA repair?

Answer 23

CTA and duplex ultrasound before discharge, at 1 month, month 6, year 1 then yearly

Question 24

Clinical presentation ruptured AAA?

Answer 24

50% present with classic triad:
• acute abdominal pain
• hypotension
• pulsatile abdominal mass

Question 25

Initial management ruptured AAA?

Answer 25

Resuscitation with permissive hypotension to maintain organ perfusion. Get ready for theatre.

Question 26

Patient selection for ruptured AAA surgical repair? (5)

Answer 26

Hardman criteria.
• age >70
• creatinine >190 mmol/l
• hb <9 g/dL
• ECG evidence of ischaemia
• loss consciousness
≥ 3 factors predict a mortality of 100% and shouldn’t be repaired

Question 27

How is surgical repair of ruptured AAA achieved?

Answer 27

Open repair: supraceliac aorta exposure and clamping
• midline laparotomy
• retract left lobe of liver to right and open gastro hepatic ligament to allow into lesser sac
• NGT used to identify esophagus and stomach. Retract to left.
• Aorta identified between crura of diaphragm. L crus may be split with cautery to allow clamp placement

EVAR: preferred
Rapid control haemorrhage by inflation aortic balloon in suprarenal aorta