Abdominal Aortic Aneurysm

Abdominal Aortic Aneurysm

Basics

Description

• Focal dilation of the aortic wall with an increase in diameter by at least 50% (>3 cm)
• 95% are infrarenal.
• Gradual expansion or rupture causes symptoms.
• Rupture can occur into the intraperitoneal or retroperitoneal spaces.
• Intraperitoneal rupture is usually immediately fatal.
• Average growth rate of 0.2 to 0.5 cm per year
• 5-year risk of rupture:
  • Aneurysms <4.0 cm: 2%
  • Aneurysms 4.0-5.0 cm: 5%
  • Aneurysms 5.0-6.0 cm: 25%
  • Aneurysms 6.0-7.0 cm: 35%
• 40-50% die before they reach the hospital.
• 50% of patients who reach the hospital alive survive.
• 5-year survival after repair is 67%.

Geriatric Considerations

• Risk increases with advanced age.
• Present in 4-8% of all patients older than 65 years
• Peak incidence:
  • Men: 5.9% at the age of 80 years
  • Women: 4.5% at the age of 90 years

Etiology

• Risk factors:
  • Male gender
  • Age >65 years old
  • Family history
  • Cigarette smoking
  • Atherosclerosis
  • Hypertension
  • Diabetes mellitus
  • Connective tissue disorders:
    • Ehlers-Danlos syndrome
    • Marfan syndrome
• Uncommon causes:
  • Blunt abdominal trauma
  • Infections of the aorta
    
  • Mycotic aneurysm secondary to endocarditis

Diagnosis

Signs and Symptoms

• Unruptured:
  • Most often asymptomatic
  • Abdominal, back, or flank pain:
    • Vague, dull quality
    • Constant, throbbing, or colicky
  • Abdominal mass or fullness
  • Palpable, nontender, pulsatile mass
  • Intact femoral pulses
• Ruptured:
  • Classic triad:
    • Pain
    • Hypotension
    • Pulsatile abdominal mass
    • Present in only 30-50% of patients
  • Systemic:
    • Syncope
    • Hypotension
    • Tachycardia
    • Evidence of systemic embolization
  • Abdomen:
    • Abdominal, back, or flank pain
    • Acute, severe, constant
    • Radiates to chest, thigh, inguinal area, or scrotum
    • Flank pain radiating to the groin in 10% of cases
    • Pulsatile, tender abdominal mass
    • Only 75% of aneurysms >5 cm are palpable
    • Abdominal tenderness
    • Abdominal bruit
    • Gastrointestinal (GI) bleeding
  • Extremities:
    • Lower-extremity pain
    • Diminished or asymmetric pulses in the lower extremities
• Complications:
  • Large emboli: acute painful lower extremity
  • Microemboli: cool, painful, cyanotic toes (blue toe syndrome)
  • Aneurysmal thrombosis: acutely ischemic lower extremity
  • Aortoenteric fistula: GI bleeding

Essential Workup

• Unstable patients:
  • Explorative surgery without further ancillary studies
  • Bedside abdominal ultrasound
• Stable symptomatic patients:
  • Abdominal CT

Tests

Lab

• CBC
• Type and cross-match blood
• Creatinine
• Urinalysis
• Coagulation studies

Imaging

• Plain radiographs:
  

  
  • Abdominal or lateral lumbar radiographs
  • Only if other tests are unavailable
  • Curvilinear calcification of the aortic wall or a paravertebral soft-tissue mass indicates abdominal aortic aneurysm (AAA) in 75% of patients.
  • Cannot identify rupture
  • Negative study does not rule out AAA.
    
    
    
• Abdominal ultrasound:
  

  
  • Highly sensitive for detecting AAA prior to rupture
  • In emergent setting, useful to determine presence of AAA only.
  • Ultrasound findings consistent with AAA are enlarged aorta greater than 3 cm or focal dilatation of the aorta.
  • Sensitivity has been reported as low as 10% following rupture.
  • Indicated in the unstable patient
    
    
• Abdominal CT scan:
  

  
  • Contrast is not necessary.
  • Will demonstrate both aneurysm and site of rupture (intraperitoneal versus retroperitoneal)
  • Allows more accurate measurement of aortic diameter
  • Indicated in stable patients only
• 
  
  
  
  Aortography:
  
  

  

  
  

  

  
  
  
  • No use in emergent evaluation
  • The presence of mural thrombi can lead to underestimation of the size of the aorta.
    
    
    
    
    

Diagnostic Procedures/Surgery

Explorative laparotomy by vascular surgeon

Differential Diagnosis

• Other abdominal arterial aneurysms (i.e., iliac or renal)
• Renal colic
• Biliary colic
• Musculoskeletal back pain
• Pancreatitis
• Cholecystitis
• Appendicitis
• Bowel obstruction
• Perforated viscus
• Mesenteric ischemia
• Diverticulitis
• GI hemorrhage
• Aortic thromboembolism
• Myocardial infarction
• Addisonian crisis
• Sepsis

Treatment

Pre Hospital

• Establish two large-bore IV lines
• Rapid transport to the nearest facility with surgical backup
• Alert ED staff as soon as possible to prepare the following:
  • Operating room
  • Universal donor blood
  • Surgical consultation

Initial Stabilization

• Two large-bore IV lines
• Crystalloid infusion
• Cardiac monitor
• Early blood transfusion

ED Treatment

For patients suspected of symptomatic AAA:

• Avoid overaggressive fluid resuscitation; this leads to increased bleeding.
• Emergent surgical consult and operative intervention
• Diagnostic tests should not delay definitive treatment.

Admission Criteria

All patients with symptomatic AAA require emergent surgical intervention and admission.

Discharge Criteria

Asymptomatic patients only

Issues for Referral

• Close vascular surgery follow up must be arranged prior to discharge.
• Instructions to return immediately:
  • With any pain in the back, abdomen, flank, or lower extremities
  • With dizziness or syncope