Abdominal Aortic Aneurysm, Emergency Medicine

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

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 Ś 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"Ł)
- 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

Diagnosis Tests & 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: á

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.

Follow-Up

Disposition

Admission Criteria
All patients with symptomatic AAA require emergent surgical intervention and admission. á
Discharge Criteria
Asymptomatic patients only á

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 áS, Jones áJ. Accuracy of emergency department ultrasound in detecting abdominal aortic aneurysm. Emerg Med J. 2006;23(10):803-804.
Choke áE, Vijaynagar áB, Thompson áJ, et al. Changing epidemiology of abdominal aortic aneurysms in England and Wales: Older and more benign? Circulation. 2012;125(13):1617-1625.
Lederle áFA, Freischlag áJA, Tassos áC, et al. Long-term comparison of endovascular and open repair of abdominal aortic aneurysm. N Engl J Med. 2012;367:1988-1997.
Rogers áRL, McCormack áR. Aortic disasters. Emerg Med Clin N Am. 2004;22:887-908.
Tibbles áC, Barkin áA. The aorta. In: Cosby áK, Kendall áJ. Practical Guide to Emergency Ultrasound. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:219-236.

Codes

ICD9

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

ICD10

I71.3 Abdominal aortic aneurysm, ruptured
I71.4 Abdominal aortic aneurysm, without rupture

SNOMED

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

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