Aortic Aneurysm, Abdominal

Key Features

Essentials of Diagnosis

• Most aortic aneurysms are asymptomatic until rupture, which is catastrophic

• Aneurysms measuring 5 cm are palpable in 80% of patients; the usual threshold for treatment is 5.5 cm

• Back or abdominal pain with aneurysmal tenderness may precede rupture

• Excruciating abdominal pain that radiates to the back

• Hypotension

General Considerations

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

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

• Aneurysms rarely cause rupture until diameter exceeds 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, and may also accompany inflammatory aneurysms

• Inflammatory aneurysms have an inflammatory peel, similar to the inflammation seen with retroperitoneal fibrosis, surrounds the aneurysm and encases adjacent retroperitoneal structures, such as the duodenum and, occasionally, the ureters

• Ruptured aneurysms

  • Severe pain

  • Hypotension

  • Free rupture into the peritoneal cavity is lethal

  • Most aneurysms have a thick layer of thrombus lining the aneurysmal sac

  • Embolization to lower extremities is rarely seen

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 also have the cardiopulmonary diseases of elderly male smokers, which include

  • Coronary artery disease

  • Carotid disease

  • Kidney impairment

  • Emphysema

• Preoperative testing may indicate the presence of these comorbid conditions

Imaging Studies

• Abdominal ultrasonography

  • Diagnostic study of choice for initial screening

  • Useful in screening 65- to 75-year-old men, but not women, who have a history of smoking

  • Repeated screening does not appear to be needed

• 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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