ESSENTIALS OF DIAGNOSIS
Most aortic aneurysms are asymptomatic until rupture.
80% of AAAs measuring 5 cm are palpable; the usual threshold for treatment is 5.5 cm.
Back or abdominal pain with aneurysmal tenderness may precede rupture.
Rupture is catastrophic: excruciating abdominal pain that radiates to the back; hypotension.
Dilatation of the infrarenal aorta is a normal part of aging. The aorta of a healthy young man measures approximately 2 cm. An aneurysm is considered present when the aortic diameter exceeds 3 cm, but aneurysms rarely rupture until their diameter exceeds 5 cm. AAAs are found in 2% of men over 55 years of age; the male to female ratio is 4:1. Ninety percent of abdominal atherosclerotic aneurysms originate below the renal arteries. The aneurysms usually involve the aortic bifurcation and often involve the common iliac arteries.
Aortic inflammation is uncommon with atherosclerotic aneurysms and may be due to inflammation from aortic vasculitis, as in Takayasu disease or Behçet disease. Rarely, inflammatory aortitis is due to infections, including Salmonella, tuberculosis, and syphilis. Periaortic inflammation without vasculitis or infection (inflammatory aneurysm) is due to retroperitoneal fibrosis, either idiopathic or secondary (IgG4-related disease).
Although 80% of 5-cm infrarenal aneurysms are palpable on routine physical examination, most aneurysms are discovered on ultrasound or CT imaging as part of a screening program or during the evaluation of unrelated abdominal symptoms.
Aneurysmal expansion may be accompanied by pain that is mild to severe midabdominal discomfort often radiating to the lower back. The pain may be constant or intermittent and is exacerbated by even gentle pressure on the aneurysm sack. Pain may also accompany inflammatory aneurysms. Most aneurysms have a thick layer of thrombus lining the aneurysmal sac, but embolization to the lower extremities is rarely seen (eFigure 12–9).
CT angiography cross sectional image of a patient with a 5.5 cm aneurysm. Note the proximity of the aneurysm to the anterior abdominal wall. These vessels are easily palpable in 80% of patients.
The sudden escape of blood into the retroperitoneal space causes severe pain and hypotension. Free rupture into the peritoneal cavity is a lethal event.
In acute cases of a contained retroperitoneal rupture, the hematocrit may be normal, since there has been no opportunity for hemodilution.
Patients with aneurysms may also have CAD, carotid disease, kidney disease, and emphysema, which ...