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Surgical Emergencies > AAA - Abdominal Aortic Aneurysm > Flashcards

AAA - Abdominal Aortic Aneurysm Flashcards

1
Q

Define: What is an AAA?

A

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

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2
Q

What is the normal diameter of the aorta?

A

2cm

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3
Q

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

A

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

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4
Q

What is the pathogenesis of AAA?

A

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

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5
Q

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

A

Left gastric
Common hepatic
Splenic

T12

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6
Q

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

A

L1
L3

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7
Q

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

A

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

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8
Q

At what level does the aorta pierce the diaphragm?

A

T12

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9
Q

What arteries do the suprarenal arteries stem from?

A

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)

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10
Q

Please state the branches of the abdominal aorta superiorly to inferiorly

A

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

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11
Q

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

A

L3 as it gets stuck on the inferior mesenteric artery

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12
Q

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

A

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

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13
Q

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

A

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

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14
Q

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

A

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

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15
Q

What aortic diameter is an indication for surgery?

A

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

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16
Q

What are the RF for AAA and its rupture?

A

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

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17
Q

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)

A

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

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18
Q

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?

A

Into the retroperitoneum
Ecchymosis (bruising)
Aorto-entericfistula

19
Q

What is the retroperitoneum

A

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.

20
Q

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

A

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

21
Q

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

A

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

22
Q

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

A

A pulsatile mass above and left of umbilicus

23
Q

What is the Triad for AAA rupture

A

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

Sudden abdominal/back/flank pain

24
Q

What is the screening protocol for AAA?

A

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

25
Q

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

A

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

26
Q

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)?

A

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

27
Q

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?

A

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

28
Q

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.

A

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.

29
Q

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

A

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

30
Q

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

A

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

31
Q

What are the complications of every surgery?

A

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

32
Q

What are the early and late complications of AAA repair?

A

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

33
Q

Define Endoleak along with its classification
How is it identified?

A

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

34
Q

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

A

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

35
Q

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

A

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

36
Q

How does a patient with a cerebral aneurysm typically present?

A

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

37
Q

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?

A

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

38
Q

What is permissive hypotension?
When would this be used?

A

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

39
Q

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

A

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

40
Q

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

A

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

41
Q

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

A

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

42
Q

Describe what you see in this image

A

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

43
Q

What is a Dacron Graft

A

Synthetic polyethylene graft used in AAA repair via EVAR

44
Q

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?

A

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

Surgical Emergencies (13 decks)

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