Abdominal Aortic Aneurysm

Pathology

• Atherosclerotic changes leads to aneurysmal dilatation of abdominal aorta
• Calcification of wall can occur
• Complications:
  • Rupture with extravasation of blood chronic or acute
  • Erosion of the adjacent vertebral bone can occur
  • Thrombus can form in the lumen
  • Emboli to distal vessels from atheromatous plaques

  The abdominal aorta was opened along the posterior wall revealing severe atherosclerosis. The anatomical features are obscured by ulcerated plaques and superimposed blood clots.

What are the imaging findings of AAA?

• Widened aortic lumen
  • Plain film:
    • Calcification of both walls at the same level with increased diameter
      • Displaced calcification of single wall may be due to tortuous undulated aorta
    • US: Widened aortic lumen > 3 cm
      • Color doppler
    • CT: Dilated aorta
  • Calcification of the aneurysm wall
  • Complications
    • Thrombus within aneurysm
    • Rupture into
      • Retroperitoneum
      • Perianeurysmal fibrosis obstructing ureter
    • Compression and or erosion of adjacent structures
      • Vertebra
    • Embolic to distal extremities

   

What imaging studies are available for abdominal aortic aneurysm?

• Ultrasound
  • Screening modality but only measures aortic diameter.
  • For an uncomplicated AAA, ultrasound has a sensitivity and specificity of 97 and 100%.
  • For a leaking or ruptured AAA, sensitivity drops to 4% and specificity remains at 100%.
• CT angiogram
  • Procedure of choice
  • Accurately defines aortic size and extent of aneurysm.
  • CT is the first choice in a patient with a classical midline sharp, tearing abdominal pain that radiates to the back, and has a midline pulsatile mass on exam.
  • CT has a sensitivity and specificity of 97% and 94%.
  • 3D reconstructed images can provide the details necessary for surgical option.
• MRI can provide similar information as a CT angiogram. Difficulty in patient staying still and time of study
• Angiogram: CT angiograms and MRI have replaced the need for angiograms.
• Plain films: Incidental recognition or suspicion of AAA.

Image Atlas for Abdominal Aortic Aneurysm

Abdominal Aortic Aneurysm

Ultrasound

Aneurysm of Abdominal Aorta

Plain film

Calcification of wall of aortic aneurysm.

CT: Abdominal Aortic Aneurysm

Calcification of wall of the aortic aneurysm.

CT: Aneurysm of descending Aorta - Eroding Vertebra

Abdominal CT and close-up of spine show abdominal aneurysm (A) with chronic erosion (arrows) of adjacent vertebra.

Ruptured Abdominal Aortic Aneurysm

CT without IV contrast shows abdominal aortic aneurysm (A) with high density blood (arrows) indicating rupture.

Abdominal Aortic Aneurysm

Angiogram

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Is there a role for interventional radiology in the management of AAA?

A permanent stent can be placed in the AAA, thus avoiding surgical risks.This procedure offers an alternative to patients who are of great surgical risk.

Stent in place

Click on the image to see the angiogram.