Abdominal Aortic Aneurysm

Key Features

Essentials of Diagnosis

• Most aortic aneurysms are asymptomatic until catastrophic rupture

• 80% of abdominal aortic aneurysms measuring 5 cm are palpable; the usual threshold for treatment is 5.5 cm

• Back or abdominal pain with aneurysmal tenderness may precede rupture

• Hypotension

• Excruciating abdominal pain that radiates to the back

General Considerations

• The aorta of a healthy young man measures approximately 2 cm

• An aneurysm is considered present when the aortic diameter > 3 cm

• Aneurysms rarely cause rupture until diameter > 5 cm

• 90% of abdominal atherosclerotic aneurysms originate below the renal arteries

• Aortic bifurcation is usually involved

• Common iliac arteries are often involved

Demographics

• Found in 2% of men over age 55

• Male to female ratio is 4:1

Clinical Findings

Symptoms and Signs

• Most asymptomatic aneurysms are discovered on ultrasound or CT imaging as part of a screening program or during the evaluation of unrelated abdominal symptoms

• Symptomatic aneurysms

  • Mild to severe midabdominal pain due to aneurysmal expansion often radiates to lower back

  • Pain may be constant or intermittent, exacerbated by even gentle pressure on aneurysm sack

  • May also accompany inflammatory aneurysms

• Ruptured aneurysms

  • Severe pain

  • Palpable abdominal mass

  • Hypotension

  • Free rupture into the peritoneal cavity is lethal

  • Rare embolization into lower extremities despite thick layer of thrombus lining the aneurysmal sac

Differential Diagnosis

• Perforated viscus, eg, peptic ulcer, appendix, gallbladder, diverticulitis

• Pancreatitis or pancreatic pseudocyst

• Urinary calculi

• Pyelonephritis

• Gastritis

• Intestinal ischemia

• Bowel obstruction

• Musculoskeletal pain

• Sudden death due to other causes, eg, ventricular fibrillation, myocardial infarction, pulmonary embolism

Diagnosis

Laboratory Tests

• Hematocrit will be normal, since there has been no opportunity for hemodilution

• Patients with aneurysms may have the following coexisting conditions, which typically occur in older men who smoke or have smoked cigarettes:

  • Coronary artery disease

  • Carotid disease

  • Kidney disease

  • Emphysema

• Preoperative testing may indicate the presence of these comorbid conditions

Imaging Studies

• Abdominal ultrasonography

  • Diagnostic study of choice for initial screening

  • Screening guidelines

    • Recommend screening in men 65–75 years old with exposure to 100 or more lifetime cigarettes

    • Conflict on whether women with the same exposure should be screened

    • Do not recommend repeated screening if the aorta shows no enlargement

    • While patients are monitored, smoking cessation and treatment of underlying hypertension, hyperlipidemia, and diabetes should be considered

• Abdominal or back radiographs: curvilinear calcifications outlining portions of aneurysm wall may be seen in approximately 75% of patients

• CT scans

  • Provide a more reliable assessment of aneurysm diameter

  • Should be done when the aneurysm nears the diameter threshold (5.5 cm) for treatment

• Contrast-enhanced CT scans

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