JC03 (Surgery) - Aortic Aneurysm

Question 1

Define aneurysm

Answer 1

□ Definition: permanent localized dilatation of an artery

with 50% increase in diameter

Question 2

Classify 4 main types of aneurysms by form

Answer 2

□ Fusiform: circumferential dilatation (more common)
□ Saccular: bulging only involves part of circumference
□ Dissecting: Blood enters space within media (false lumen)
□ Varicose aneurys: tortuous dilatation

Question 3

Classify true and false aneurysms

Answer 3

True:
Lined by intact attenuated vessel wall formed by all 3 layers (intima, media, adventitia)

False/ pseudo:
Lined by laminated thrombus and compressed fibrous tissue

Question 4

Classify aneurysms by etiologies

Answer 4

□ Atheromatous: commonly affects abdominal aorta, popliteal and femoral arteries

□ Mycotic: aneurysm resulting from microbial arteritis
(subacute bacterial endocarditis, bacteremia)

□ Traumatic (a/w false aneurysms)

□ Connective tissue diseases, eg. Marfan’s syndrome

□ Others: syphilitic, congenital, anastomotic (at AV fistulas)

Question 5

Most common form of aneurysm

Answer 5

true fusiform atherosclerotic aneurysms

Question 6

Complications of aneurysms

Answer 6

→ Compression, eg. RLN compression by thoracic aortic aneurysm
→ Thrombosis and embolism
→ Infection
→ Rupture

Question 7

Most common location of abdominal aortic aneurysm

Answer 7

Area between infra-renal artery area and the bifurcation of aorta
95% with associated atherosclerosis (strong association but not pathogenic)

Question 8

Etiology of AAA

Answer 8

Multifactorial, loss of vascular structural proteins leading to loss of wall strength

□ Mechanical: degeneration (old) , hypertension

□ Smoking: Enhanced proteolytic activity of matrix metalloproteinase (MMP) → dissolution of arterial wall ECM

□ Connective tissue disease e.g. Marfan’s syndrome

□ Cystic medial necrosis

□ Postsurgical anastomotic disruption

□ Vasculitis

□ Mycotic aneurysm (Staph aureus, Syphillis, Salmonella, fungal infections)

Question 9

Symptoms of AAA

Answer 9

Due to local compression:

• Pain at abdominal, back due to stretching of aneurysm sac
• Radicular pain in thigh and groin (esp in distal aneurysms, due to nerve compression)
• GI, urinary, venous obstruction

Due to distal embolization → acute ischaemic limb

Question 10

Classical Triad of symptoms for AAA rupture

Answer 10

→ Severe abdominal and/or back pain
→ Hypotension
→ Pulsatile abdominal mass

Question 11

How to define location of AAA in PE

Answer 11

Confirm AAA:
→ Mass above umbilicus
→ Expansile pulsation

Upper and lower border

• Can get above → infrarenal
• Can get below → does not involve iliac artery

Question 12

Modalities of imaging for AAA (3)

Answer 12

Plain C/AXR: calcified rim + widened mediastinum
USG
CT angiogram: surgical planning

Question 13

Management options for AAA ** (conservative and surgical)

Answer 13

Conservative management:

• Active surveillance by USG every 6 months, elective repair >5.5cm
• Lifestyle: smoking cessation, ↑exercise

Surgical management:
□ Open repair: aneurysmectomy + inlay graft
□ Endovascular aneurysm repair (EVAR):
aortic stent graft ± IIA embolization

Question 14

Growth rate and rupture risk of AAA per year

Answer 14

Growth rate: ~5mm/y

Risk of rupture at 5y: 20% if <5cm, 50% if >5cm

Question 15

Indications for surgical management of AAA

Answer 15

Size: >5cm to 5.5cm diameter
Increase in aneurysm size by > 0.5 cm within 6 months, regardless of size
Chronic abdominal pain/ impeding rupture
Thromboembolic complications present
Iliac or femoral artery aneurysm that causes lower-limb ischemia

(Aneurysms > 4.5 cm in patients with Marfan syndrome)

Question 16

Contraindications to surgical management of AAA

Answer 16

All AAA >5cm should be operated on unless

→ Medically unfit (operative mortality > risk of rupture)
→ Limited life expectancy

Question 17

Compare efficacy of open vs EVAR surgery for AAA

Answer 17

EVAR generally has
→ Better short-term outcome
→ Similar long-term outcome due to durability issue, higher re-intervention rate

Question 18

Outline pre-operative preparation for AAA repair

Answer 18

1) General: blood tests, ECG, CXR
2) CTA: assessment of anatomy for any variants, eg. horseshoe kidney, retro-aortic renal vein
3) Cardiac: assessment or intervention
4) Transfusion prep: T/S and 6 units of blood ready
5) Thromboprophylaxis: IV heparin (to prevent trash limb) ± IV protamine after surgery

Question 19

Complications that cause the highest mortality in AAA repair

Answer 19

MI due to stress by clamping/declamping (leading cause of early postoperative death)
Respiratory: ARDS
acute kidney injury (leading cause of late postoperative death)

Question 20

Early complications of Open AAA repair

Answer 20

Hemorrhage

Iatrogenic injury to internal organs

Tissue ischemia:
- Bowel ischemia (ligation of mesenteric vessels, esp. colon)
- Paraplegia after spinal ischemia (ligation of costal or lumbar arteries in throacic AA)
- Sexual dysfunction (ligation of retroperitoneal vessels)
- Trash foot (ligation of iliac arteries)
- Renal failure (embolism and decrease renal perfusion)

Question 21

Late iatrogenic complications of Open AAA repair (3)

Answer 21

Graft infection

Anastomotic aneurysm

Graft-duodenal fistula

Question 22

Early graft-related complications of EVAR AAA repair

Answer 22

Entry site: thrombosis, dissection, haematoma, embolization

Retroperitoneal haematoma

Endoleak: persistent flow into aneurysm sac after EVAR

Graft migration (proximal aortic neck dilatation)

Separation of components

Graft limb kinking and occlusion

Endograft infection

Question 23

Systemic complications of EVAR AAA repair

Answer 23

Cardiac: MI

Respiratory: ARDS

Contrast-related: allergy, nephropathy

Ischemia: visceral organs, spine

Post-implantation syndrome: inflammatory for 7-10 days, self-limiting

Question 24

4 sites of AAA rupture

Answer 24

Retroperitoneal (80%), i.e. left posterolateral wall 2 to 4 cm below the renal arteries. most common*

Intraperitoneal (20%), i.e. anterior rupture

Duodenal (rare)

IVC (rare)

Question 25

Signs of retroperitoneal or intraperitoneal bleeding from ruptured AAA

Answer 25

→ Cullen’s sign: paraumbilical bruising
→ Grey Turner sign: flank bruising
→ Fox’s sign: ecchymosis of proximal thigh
→ Bryant’s sign: discoloration of scrotum

Question 26

D/dx of retroperitoneal or intraperitoneal bleed

Answer 26

□ Ruptured mycotic aneurysm
□ Ruptured HCC (esp if young, AAA seldom occurs in <40y)
□ Ruptured ectopic pregnancy

Question 27

Management of ruptured AAA

Answer 27

1. Diagnosis: USG or CTA
2. Resuscitation:
   - Large bore IV cannula
   - Cross-match blood, fresh frozen plasma (NO ADRENALINE)
   - Achieve permissive hypotension* to limit bleeding
3. Surgery:
   - Clamping of aorta
   - Emergency repair:
   EVAR (stable- CTA, unstable- Aortic balloon)
   Open surgery (unstable)

Question 28

Complications of ruptured AAA

Answer 28

□ Massive blood loss and transfusion-related S/E, eg. DIC*, hypothermia

□ Cardiorespiratory* complications due to haemodynamic stress

□ Ischaemic* complications:
→ Renal failure due to shock or suprarenal clamping
→ Bowel ischaemia: much higher risk than in non - ruptured AAA

□ Paralytic ileus* due to retroperitoneal haematoma

□ Abdominal compartment syndrome* due to reperfusion injury

Question 29

Determinants of open vs EVAR AAA repair

Answer 29

Anatomical variance:

→ Neck: suitable length (>10-15mm), diameter (15-20% smaller than graft) and angulation (<60o) for graft landing zone

→ Iliac artery: adequate length (>15-20mm) and diameter (8-22mm) for graft landing

→ Access: minimal tortuosity and narrowing

→ Others: calcification, preservation of IIA

Question 30

Define 5 types of Endoleaks

Answer 30

Type I and III - high pressure endoleaks

Type II - reflux leak from visceral arteries

Type IV - porosity of graft fabric

Type V - unknown cause

Types I and III are high-pressure leaks → warrant endovascular repair (eg. extension limb, aortic cuff)