AAA - Abdominal Aortic Aneurysm

Question 1

Define: What is an AAA?

Answer 1

Abnormal dilatation of aorta becoming >3cm or >50% of normal diameter

Question 2

What is the normal diameter of the aorta?

Answer 2

2cm

Question 3

What is meant by a true AAA? How does that differ from false?

Answer 3

A true AAA is one that contains all 3 layers of the vessel wall whereas in a false it is only some of the layers => extravasation of blood into an aneurysmal sac

Question 4

What is the pathogenesis of AAA?

Answer 4

Transmural inflammation causing abnormal collagen remodeling
=> Loss of elastin and smooth muscle cells
=> Aortic wall thinning => weaker => expansion

Question 5

At what level is the celiac trunk and what branches does it give off?

Answer 5

Left gastric
Common hepatic
Splenic

T12

Question 6

At what levels does the aorta give off the superior and inferior mesenteric arteries

Answer 6

L1
L3

Question 7

At what level does the aorta bifurcate? What does it bifurcate into?

Answer 7

L4
Bifurcates into the left and right common iliac (which then each split into internal and external) as well as a median sacral artery

Question 8

At what level does the aorta pierce the diaphragm?

Answer 8

T12

Question 9

What arteries do the suprarenal arteries stem from?

Answer 9

Superior suprarenal comes off the (inferior) phrenic artery (T12)
Middle suprarenal comes directly off the aorta (T12) at the level of the celiac
Inferior suprarenal comes off the renal arteries (L1)

Question 10

Please state the branches of the abdominal aorta superiorly to inferiorly

Answer 10

Phrenic
Celiac Trunk (T12)
Suprarenal artery
Renal arteries
Superior mesenteric (L1)
Gonadal Arteries
Inferior Mesenteric (L3)
Bifurcation (L4)

Question 11

At what level is the horseshoe kidney typically located? Why?

Answer 11

L3 as it gets stuck on the inferior mesenteric artery

Question 12

What are the 2 etiological types of AAA?
Which is the more common one?

Answer 12

Fusiform (more common) => Degenerative => normal pathogenesis of abnormal collagen remodeling and loss of elastin
Saccular => infective (bacteremia, endocarditis, mycotic aneurysm)

Question 13

What classification is used to classify the location of the aneurysm? (go into detail)
Which is the most common type and name it.

Answer 13

Crawford Classification
Type 1: Origin of left subclavian -> Suprarenal
Type 2: Subclavian -> Bifurcation
Type 3: Distal thoracic -> bifurcation
Type 4: All Under Diaphragm

95% of AAA are infrarenal => Type 4

Question 14

What are the modifiable and non-modifiable risk factors of PVD (Peripheral vascular disease)?

Answer 14

Modifiable: Smoking, HTN, dyslipidemia, hypercholesterolemia, previous stroke/MI, Hyperhomocysteinemia
Non-modifiable: Male, Age >55, Family Hx

Question 15

What aortic diameter is an indication for surgery?

Answer 15

Diameter >5.5 or expansion rate of 0.5cm/6 months

Question 16

What are the RF for AAA and its rupture?

Answer 16

PVD RF especially smoking (x10) and HTN (x2)
Collagen/Elastin Defects: Marfan’s or Ehlers Danlos Syndrome
Diameter >5.5 or expansion rate of 0.5cm/6 months
Aortitis (from bacteremia, endocarditis, mycotic aneurysm)
Other: Diabetes, GCA, Polyarteritis nodosa, Coarctation of the aorta

Question 17

An aorto-enteric fistula may be caused primarily by AAA itself or secondarily post-op (especially EVAR). What is the cause of primary aorto-enteric fistula? (not a disease, physiologically)
What can this lead to? (2)

Answer 17

A long-standing leak causes the formation of the aorto-enteric fistula. This leads to
Upper GI bleed
High output HF

Question 18

As part of the pathogenesis of AAA, a leak occurs draining blood. This leak typically drains where?
What clinical feature of AAA occurs as a result of this?
What complication of AAA does this cause?

Answer 18

Into the retroperitoneum
Ecchymosis (bruising)
Aorto-entericfistula

Question 19

What is the retroperitoneum

Answer 19

Space behind the abdomen. This is the space where most of the ecchymosis happens in AAA as a leak or a ruptured AAA accumulates blood there showing bruising.

Question 20

50% of AAA patients are found incidentally on exam or imaging while asymptomatic. What are the clinical features of AAA? (incl those with rupture)

Answer 20

Sudden Onset
Abdominal/back/flank pain
Acute limb ischemia (distal peripheral embolization)/Bluetoe syndrome
Upper GI bleed (aorto-enteric fistula)=>malaena +/- hemoptysis
Hypotension/Syncope
Ecchymosis!!! -> Retroperitoneal hematoma/ruptured AAA

Question 21

What is seen in this image?
What may cause this (2)

Answer 21

Image showing retroperitoneal ecchymosis typically seen in ruptured AAA and hemorrhagic pancreatitis

In this picture there is Cullen’s sign which is periumbilical. This has the same causes + ectopic pregnancy

Question 22

50% of AAA patients are found incidentally on exam or imaging while asymptomatic. On exam, what would indicate an AAA?

Answer 22

A pulsatile mass above and left of umbilicus

Question 23

What is the Triad for AAA rupture

Answer 23

Sudden onset
Hypotension/syncope
Pulsatile mass (not always present)

Sudden abdominal/back/flank pain

Question 24

What is the screening protocol for AAA?

Answer 24

4-4.5cm -> annual US
>4,5 -> Bi-annual US

Question 25

A patient presents to the ED with sudden onset 10/10 abdominal pain. Quickly give DDx

Answer 25

AAA
Ischemic Bowel
Perforated PUD
Acute Pancreatitis
Nephrolithiasis
Pyelonephritis
Extra: Appendicitis, peritonitis, trauma, Inferior MI

Question 26

On examination of a patient with abdominal and back pain with a history of CKD, you notice a pulsatile mass over and to the left of the umbilicus. What imaging can you perform outlining why for each (3)?

Answer 26

Initially US but that can only identify the presence of an aneurysm but not the extent of it nor need for repair
CT abdomen with IV contrast will define its location, extent, !endoleak or any leak!, need for repair, and suitability for EVAR. This will not be performed here because the patient has CKD
MRI: IV contrast is nephrotoxic => we use this for patients with renal insufficiency. cannot detect endoleak

Question 27

On examination of a patient with abdominal and back pain with a history of CKD, you notice a pulsatile mass over and to the left of the umbilicus. On Contrast CT abdomen, the patient has an AAA with a diameter of 4.5. What is your management plan?

Answer 27

Conservative management
1) Modifiable RFs: Reduce smoking, dietitian consult, exercise, medication adherence esp diabetes
2) Statins, Beta blockers

Question 28

On examination of a patient with abdominal and back pain with a history of CKD, you notice a pulsatile mass over and to the left of the umbilicus. The patient is stable. On Contrast CT abdomen, the patient has an AAA with a diameter of 6.2cm. What choices of management do you have (2)? Explain each, comparing them.

Answer 28

Over 5.5 threshold for surgery. If the patient is stable, elective surgery has 2 options (if rupture => emergency)

Open repair: Laparotomy (large midline incision) using a synthetic Dacron Graft to repair the aneurysm. The aorta is clamped below the renal arteries to prevent renal ischemia. This is associated with higher mortality due to the major insults of surgery which are laparotomy (large incision), clamping, and ischemia-reperfusion.
More suitable for patients with renal insufficiency

EVAR: Endovascular aneurysm repair involves a small groin incision where stent is inserted through and placed over the aneurysmal segment under direct radiological guidance (=> large use of contrast).
A major complication of EVAR is the Endoleak
More suitable for older age group

Patient has CKD => high levels of contrast used in EVAR is not recommended. Open repair is then chosen.

Question 29

During an open repair laparotomy, where does the surgeon clamp the aorta? Why?

Answer 29

The aorta is clamped below the renal arteries to prevent renal ischemia

Question 30

What is the main complication of EVAR? How does this affect PATIENT OUTCOMES

Answer 30

EVAR may cause an endoleak which leads to the high early re-intervention (25%). This also requires lifelong monitoring which occurs after 1 month, 3 months, 6 months, 1 year, and then yearly

Question 31

What are the complications of every surgery?

Answer 31

Pain, wound infection, hemorrhage, DVT/PE, death

Question 32

What are the early and late complications of AAA repair?

Answer 32

Typical pain, wound infection, hemorrhage, DVT/PE, death
Early:
Cardiac arrhythmias and MI (common)
Pneumonia, atelectasis, resp failure
Bowel, limb and spinal cord ischemia
Renal dysfunction (esp EVAR)
Impaired sexual dysfunction (25%)

Late:
Graft infection
!!Acute limb ischemia from Graft limb occlusion
Endoleak (EVAR)
Hernia (from ileus/constipation from bowel limb ischemia)
Aorto-enteric fistula (Upper GI Bleed)
High output cardiac failure

Question 33

Define Endoleak along with its classification
How is it identified?

Answer 33

Endoleak: Persistent blood floe into an aneurysmal sac (False AAA) after EVAR
Classified as:
Type 1: Leak at attachment site of graft
Type 2: Backflow of blood into sac by collateral vessels (Inferior mesenteric and lumbar arteries)
Type 3: Leak through defect in graft
Type 4: Leak through fabric of graft due to porosity
Type 5: Expansion of aneurysm sac without evidence of leak on imaging

Classified via CT w/ contrast

Question 34

Give 4 other types of aneurysms other than AAA. Which one is associated with AAA the most? How is it identified?

Answer 34

Thoraco-abdominal
Femoral
Popliteal (most associated with AAA). Identified by pulsatile mass being bilateral in the popliteal fossa
Carotid
Cerebral
Iliac
Visceral

Question 35

How does a patient with Thoraco-abdominal aneurysm typically present?

Answer 35

Typically asymptomatic but may present with chest and back pain, acute aortic regurg., and acute HF (palpitations, oedema, pulm..)

Question 36

How does a patient with a cerebral aneurysm typically present?

Answer 36

Asymptomatic until rupture. Headaches, reduced visual acuity, facial pain

Question 37

On examination of a patient with abdominal and back pain, you notice a pulsatile mass over and to the left of the umbilicus. The patient is unstable. What imaging would you use to quickly confirm this? What is your management plan?

Answer 37

US will quickly determine this.
1) Admit to hospital
2) ABCDE: Send out FBC w/differentials, U&E, CRP, LFTs, and coag profile, ABG
3) NPO for all, NG tube if vomiting
4) O2 if in doubt until ABG becomes available (15L 100% O2 via non-rebreather mask)
5) 2x large bore, IV fluids at 100ml/hr until losses worked out via intake/output chart + urinary catheter (Do not give aggressive fluids to prevent worsening rupture)
6) Type and save, group and hold, Group and cross match 10 units of blood. If needed give in 1:1:1 aiming for Hb>8 and >10 in CVD
7) Analgesia (Paracetamol, NSAIDS, Morphine/oxynorm/oxycontin)
8) Antiemetics if needed (Ondansetron)
9) Antibiotics: Coamox/pip taz + Gent/Metronidazole
10) DVT prophylaxis (TEDs, Clexane, LMWH)

Alert vascular surgeon, anesthetist, theatre, ICU
If patient is fit for surgery (anesthetist) then gain consent if possible, transfer to theatre for surgery (vascular surgeon) then ICU care
If patient is not fit then give supportive therapy and prepare for palliative care

Question 38

What is permissive hypotension?
When would this be used?

Answer 38

It is the act of maintaining a blood pressure lower than physiological levels in a patient that has suffered from hemorrhagic blood loss.

Question 39

What is an an important consideration in an emergency AAA rupture when administering fluids?

Answer 39

Do not give aggressively hydrate the patient, instead go for permissive hypotension to avoid worsening the rupture

Question 40

Why is a urinary catheter administered when treating a ruptured AAA?

Answer 40

It is used to monitor for hypovolemic shock (<0.5ml/kg/hr). Renal complications are very common and many patients require dialysis for life.

Question 41

What is meant by free vs contained rupture of the AAA?

Answer 41

A free rupture is one that bleeds directly into the peritoneal cavity without a tamponade => these patients typically die instantly and do not make it to hospital

A contained rupture is one that bleeds into the retroperitoneum => temporary tamponade formed by surrounding tissue => these patients are the ones typically seen in hospital

Question 42

Describe what you see in this image

Answer 42

Axial CT-Angio showing intra-aortic contrast extravasating through the site of rupture and large retroperitoneal haematoma (you can see some white getting out from the aorta to the right. You can tell it’s RETROPERITONEAL because the left psoas muscle has been obliterated and the left kidney has been moved due to bleeding

Question 43

What is a Dacron Graft

Answer 43

Synthetic polyethylene graft used in AAA repair via EVAR

Question 44

MRI is typically used over CT angio in patients with end-stage kidney disease. Concerning AAA, what will the MRI not detect that the CT angio would?

Answer 44

blood leak/endoleak. Important before surgery and also for followup after EVAR