Abdominal Aortic Aneurysm

General Considerations

• Focal widening >3 cm
• Normal size of abdominal aorta >50 years of age:
  • About 2 cm
    
    
  Prevalence:
  
  
  • Increases with age
  • Greater with atherosclerotic disease
  • Male predominance
  • Whites: Blacks = 3:1
    
    
• Risk factors:
  
  
  • male
  • age >75 years
  • white race
  • prior vascular disease
  • hypertension
  • cigarette smoking
  • family history
  • hypercholesterolemia

Associated with:



• visceral + renal artery aneurysm (2%)
• isolated iliac + femoral artery aneurysm (16%)
  • common iliac (89%), internal iliac (10%), external iliac (1%)
• stenosis / occlusion of celiac trunk / SMA (22%)
• stenosis of renal artery (22-30%)
• occlusion of inferior mesenteric artery (80%)
• occlusion of lumbar arteries (78%)
• Growth rate of aneurysm of 3-6 cm in diameter:
  • 0.39 cm / year
    
    

Clinical

• asymptomatic (30%)
• abdominal mass (26%)
• abdominal pain (37%)
  
  
• Location
  
  
  • infrarenal (91-95%) with extension into iliac arteries (66-70%)
    
    
Imaging findings


• Plain film
  • mural calcification (75-86%)
• US:>98% accuracy in size measurement
• CT-non-contrast enhanced
  • perianeurysmal fibrosis (10%), may cause ureteral obstruction
  • "crescent sign" = peripheral high-attenuating crescent in aneurysm wall (= acute intramural hematoma) = sign of impending rupture
• CT-contrast-enhanced
  • ruptured aneurysm
    • anterior displacement of kidney
    • extravasation of contrast material
    • fluid collection / hematoma within posterior pararenal + perirenal spaces (see below)

Abdominal Aortic Aneurysm. There is a large contrast-containing abdominal aortic aneurysm just anterior to the spine with evidence of extraluminal extravasation of contrast along the left paravertebral gutter.

• free intraperitoneal fluid
• contained leak
  • laminated mural calcification
  • periaortic mass of mixed / soft-tissue density
  • lateral "draping" of aneurysm around vertebral body
    
    
• Angio
  
  
  • focally widened aortic lumen >3 cm
  • apparent normal size of lumen secondary to mural thrombus (11%)
  • mural clot (80%)
  • slow antegrade flow of contrast medium
• Contained rupture = extraluminal hematoma / cavity
  • absent parenchymal stain = avascular halo
  • displacement + stretching of aortic branches
    
    
• Complications:
  
  
  • Rupture (25%)
    • into retroperitoneum: commonly on left
    • into GI tract: massive GI hemorrhage
    • into IVC: rapid cardiac decompensation
      • Incidence: aneurysm <4 cm in 10%, 4-5 cm in 23%, 5-7 cm in 25%, 7-10 cm in 46%, >10 cm in 60%
      • Symptoms of rupture
        • sudden severe abdominal pain ± radiating into back
        • faintness, syncope, hypotension
        • Prognosis:64-94% die before reaching hospital
        • Increased risk: size >6 cm, growth >5 mm / 6 months, pain + tenderness
  • Peripheral embolization
  • Infection
  • Spontaneous occlusion of aorta
    
    
• Prognosis:17% 5-year survival without surgery
  • 50-60% 5-year survival with surgery
    
    
• Treatment
  
  
  • surgery recommended if >5 cm in diameter;
  • 4-5% surgical mortality for nonruptured
    • 30-80% for ruptured aneurysm
      
      
• Postoperative Complications
  
  
  • Left colonic ischemia (1.6%) with 10% mortality
  • Renal failure (14%)
  • 0-8% mortality rate for elective surgery

Abdominal Aortic Aneurysm. Three-dimensional CT reconstruction show a saccular dilatation of the abdominal aorta just distal to the renal arteries, not extending into the femoral arteries.

Abdominal Aortic Aneurysm. There is calcification in the left lateral wall of a huge, bi-lobed abdominal aortic aneurysm (red arrows). Incidental note is made of gallstones in the right upper quadrant (white arrow).