ABDOMINAL AORTIC ANEURYSM

 ABDOMINAL AORTIC ANEURYSM (AAA)

Aortic Aneurysm

History

 ° Male:female ratio is 4:1

° 5–10% of males over 65 years of age have AAA

° High incidence in patients with peripheral arterial aneurysm (popliteal, femoral)

° Ruptured AAA – clinical suspicion

- elderly male with severe back or abdominal pain

- may radiate to groin.

Signs & Symptoms

What is the most common symptoms in patients with abdominal aortic aneurysm ?

° Most are asymptomatic and found on other imaging studies

° pulsatile abdominal mass in less than 30% of patients with significant AAA

° Tender abdominal mass is suggestive of symptomatic aneurysm

° examine for associated peripheral aneurysms (femoral, popliteal)

° Unusual presentations:

- atheroembolism to lower extremities

- thrombosis (sudden severe ischemia of legs)

- high output CHF from aortocaval fistula

- GI bleeding from primary aorto-enteric fistula

° Ruptured AAA

- Pulsatile mass + hypotension

- abdominal/back/groin pain + hypotension

Tests

Laboratory examination

° None

Imaging

° Ultrasound for screening

° CT scan is best test for aneurysms being considered for repair

° Defines : associated iliac aneurysms, eligibility for endovascular repair, possible suprarenal extension

° Conventional MRI has no advantage over CT for AAA

° Angiography is not used for diagnosis (can miss AAA due to normal lumen)

Angiography (contrast or MR) indicated preoperatively in patients with:

- clinical suspicion of concurrent renal artery stenosis (severe hypertension, elevated creatinine)

- mesenteric occlusive disease (post-prandial pain)

- significant lower extremity occlusive disease (claudication + ankle/brachial index<0.7).

° Ruptured AAA: if diagnosis is unclear (no mass):

- Emergency ultrasound

- helpful only if aorta is clearly seen and completely normal

- often not helpful due to bowel gas and patient discomfort

- cannot rule out a leak from AAA

- CT scan

- Best test when diagnosis of AAA is unclear

- Emergency non-contrast scan of abdomen

- Intravenous contrast increases post-op renal failure and is not needed to see AAA or leak

- Oral contrast not required

DIFERENTIAL DIAGNOSIS

Ruptured AAA

° most common misdiagnosis is kidney stone

° second most common is musculoskeletal back pain; high suspicion of AAA with new onset or change in chronic back pain

° other:

- appendicitis (associated GI symptoms)

- diverticulitis (fevers, GI symptoms, focal left sided tenderness)

- aortic dissection (ripping pain, extends into chest and upper back)

- incarcerated hernia (physical exam, CT scan if exam inconclusive)

MANAGEMENT

What to Do First

° Emergent (immediate) operation in patients with abdominal pain and hypotension due to ruptured AAA

° Emergent non-contrast CT scan in patients with symptoms suggestive of ruptured AAA

General Measures

° Rule out ruptured AAA first in all patients with suggestive symptoms as it is the most rapidly lethal diagnosis if missed.

° Risk/benefit ratio of elective repair is contingent upon low operative mortality (less than 5%)

SPECIFIC THERAPY 

Indications

° Most patients

- Elective repair if diameter in any orientation is 5 to 5.5 cm

- Repair if serial scans (either ultrasound or CT) demonstrate rapid growth (> 1 cm/year) or saccular growth

- Urgent repair in patients with symptoms (tenderness)

- Repair associated lesions (renal, visceral or peripheral occlusive disease) concurrently if indicated

° Poor-risk patients

- consider endovascular repair

- discuss with patient/family outcome if not repaired

- (Risk of rupture is 2–3% per year at 5 cm, and may not be significant relative to other co-morbidities)

Treatment Options

° Operative repair

- Most durable treatment

- Little difference between transperitoneal and retroperitoneal repairs

- Intraoperative pulmonary artery catheters in patients with poor ejection fraction or CHF

Side Effects and Contraindications

° Operative repair

- Perioperative mortality should be less than 5%

- Complications

- Myocardial infarction:

- Clinical indices (Goldman criteria, Eagle criteria) are predictive of risk, but persantine thallium scanning is not.

- MI after elective repair is rarely fatal

- Ischemic colitis seen more often after ruptured AAA with hypotension

- Renal failure seen after repair of ruptured and suprarenal AAA. Associated with high mortality (50%)

° Contraindications

- Expected survival less than 50% at 5 years due to associated cardiovascular disease.

- Lower mortality and morbidity than open repair.

° Less durable than standard repair

° Absolute Contraindications:

- Bilateral common iliac artery aneurysms

- Pararenal or suprarenal aneurysm

- Angulation, thrombus or dilation of infrarenal neck

- Iliac occlusion or stenosis precluding transfemoral access.

° Relative contraindications 

- Long term anticoagulation (higher risk of endoleak).

- Associated occlusive disease requiring treatment

Specific Complications :

° Endoleak

- Persistent arterial flow in aneurysm sac due to: failure of device to seal to arterial wall (Type I), back flow from branch vessel (Type II) or leak through graft material (Type III)

° Post-implant fever

- Occurs 12–48 hours after implant; not due to infection

follow-up

During Treatment

° Follow AAA less than 5 cm with serial ultrasound or CT scans 6–12 months, or more frequently if there is rapid change in size.

Routine

° Patients undergoing endovascular repair require lifelong yearly CT scan to monitor position and seal of device

complications and prognosis

Complications

°  Myocardial Infarction

° Renal failure

-  Poor prognosis (50% mortality). Treatment is supportive. Usually

resolves (ATN)

°  Ischemic colitis

-  Diagnose by bedside sigmoidoscopy. Colectomy for full-thickness ischemia; serial endoscopy for mucosal ischemia

which often resolves. May cause late ischemic strictures.

° Endoleak 

- Diagnosed on post-op CT scan or angiogram. Treatment is usually endovascular.