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.
  • Rapid expansion or rupture causes symptoms.
  • Rupture can occur into the intraperitoneal or retroperitoneal spaces
  • Intraperitoneal rupture is usually immediately fatal
  • Average growth rate of 0.2–0.5 cm/yr
  • Of ruptures:
    • 90% overall mortality
    • 80% mortality for patients who reach the hospital
    • 50% mortality for patients who undergo emergency repair

Geriatric Considerations
  • Risk increases with advanced age.
  • Present in:
    • 4–8% of all patients older than 65 yr
    • 5–10% of men 65–79 yr old
    • 12.5% of men 75–84 yr old
    • 5.2% of women 75–84 yr old

Etiology

  • Risk factors:
    • Male gender
    • Age >65 yr
    • Family history
    • Cigarette smoking
    • Atherosclerosis
    • HTN
    • Diabetes mellitus
    • Connective tissue disorders:
      • Ehlers–Danlos syndrome
      • Marfan syndrome
  • Uncommon causes:
    • Blunt abdominal trauma
    • Congenital aneurysm
    • Infections of the aorta
    • Mycotic aneurysm secondary to endocarditis
  • Rupture risk factors:
    • Size (annual rupture rates):
      • Aneurysms 5–5.9 cm = 4%
      • Aneurysms 6–6.9 cm = 7%
      • Aneurysms 6.9–7 cm = 20%
    • Expansion:
      • A small aneurysm that grows >0.5 cm in 6 mo is at high risk for rupture.
    • Gender:
      • For aneurysms 4.0–5.5 cm, women have 4× higher risk of rupture compared to men with similar sized aneurysms.

Diagnosis

Signs and Symptoms

History
  • Abdominal, back, or flank pain:
    • Vague, dull quality
    • Constant, throbbing, or colicky
    • Acute, severe, constant
    • Radiates to chest, thigh, inguinal area, or scrotum
    • Flank pain radiating to the groin in 10% of cases
  • Lower extremity pain
  • Syncope, near-syncope
  • Unruptured are most often asymptomatic

Physical Exam
  • Unruptured:
    • Abdominal mass or fullness
    • Palpable, nontender, pulsatile mass
    • Intact femoral pulses
  • Ruptured:
    • Classic triad (only 1/3 of the cases):
      • Pain
      • Hypotension
      • Pulsatile abdominal mass
    • Systemic:
      • Hypotension
      • Tachycardia
      • Evidence of systemic embolization
    • Abdomen:
      • Pulsatile, tender abdominal mass
      • Flank ecchymosis (Grey Turner sign) indicates retroperitoneal bleed.
      • Only 75% of aneurysms >5 cm are palpable.
      • Abdominal tenderness
      • Abdominal bruit
      • GI bleeding
    • Extremities:
      • 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:
    • Bedside abdominal US
    • Explorative surgery without further ancillary studies
  • Stable, symptomatic patients:
    • Abdominal CT

Diagnostic Tests and Interpretation

Lab
  • Type and cross-match blood
  • CBC
  • 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:
    • 100% sensitive and 92–99% specific for detecting AAA prior to rupture
    • In emergent setting, useful to determine presence of AAA.
    • Ultrasound findings consistent with AAA are enlarged aorta >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 to make the diagnosis but CT angiogram is required for surgical planning for an endovascular approach
    • Will demonstrate both aneurysm and site of rupture (intraperitoneal vs. retroperitoneal)
    • Allows more accurate measurement of aortic diameter

Differential Diagnosis

  • Other abdominal arterial aneurysms (i.e., iliac or renal)
  • Aortic dissection
  • 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
  • Spinal cord compression

Treatment

Pre Hospital

  • Establish 2 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/Therapy

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

Ed Treatment/Procedures

For patients suspected of symptomatic AAA:
  • Avoid over aggressive fluid resuscitation; this leads to increased bleeding
  • Emergent surgical consult and operative intervention
  • Laparotomy versus endovascular aortic repair (EVAR) by vascular surgeon
  • Diagnostic tests should not delay definitive treatment.

Ongoing Care

Disposition

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

Discharge Criteria
Asymptomatic patients only

Follow-Up Recommendations

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

Pearls and Pitfalls

  • AAA should be on the differential for any patient presenting with pain in the abdomen, back, or flank.
  • Symptomatic AAA requires immediate treatment. Do not delay definitive care for extra studies.
  • A hemodynamically unstable (i.e., hypotensive) patient should not be taken for CT scan.

Additional Reading

  • Bentz S, Jones J. Accuracy of emergency department ultrasound in detecting abdominal aortic aneurysm. Emerg Med J. 2006;23(10):803–804.  [PMID:16988313]
  • Choke E, Vijaynagar B, Thompson J, et al. Changing epidemiology of abdominal aortic aneurysms in England and Wales: Older and more benign? Circulation. 2012;125(13):1617–1625.  [PMID:22361325]
  • Lederle FA, Freischlag JA, Tassos C, et al. Long-term comparison of endovascular and open repair of abdominal aortic aneurysm. N Engl J Med. 2012;367:1988–1997.  [PMID:23171095]
  • Rogers RL, McCormack R. Aortic disasters. Emerg Med Clin N Am. 2004;22:887–908.
  • Tibbles C, Barkin A. The aorta. In: Cosby K, Kendall J. Practical Guide to Emergency Ultrasound. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:219–236.

See Also

  • Aortic Dissection
  • Peripheral Artery Disease

Codes

ICD-9

  • 441.3 Abdominal aneurysm, ruptured
  • 441.4 Abdominal aneurysm without mention of rupture

ICD-10

  • Abdominal aortic aneurysm, ruptured
  • Abdominal aortic aneurysm, without rupture

SNOMED

  • 233985008 Abdominal aortic aneurysm (disorder)
  • 14336007 Ruptured abdominal aortic aneurysm

Authors

Daniel J. Henning
Jason C. Imperato
Carlo L. Rosen


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