High-attenuating crescent in abdominal aortic aneurysm wall at CT: a sign of acute or impending rupture

Radiology. 1994 Aug;192(2):359-62. doi: 10.1148/radiology.192.2.8029397.


Purpose: To determine whether a peripheral high-attenuating crescent in an abdominal aortic aneurysm (AAA) on unenhanced computed tomographic (CT) scans is a sign of impending or active aneurysm rupture.

Materials and methods: CT scans were reviewed of 149 consecutive patients operated on because of AAA who had undergone preoperative unenhanced CT scanning. The presence of a peripheral high-attenuating crescent on CT scans was correlated with surgical findings of aneurysm complication. Aneurysm diameter was correlated with presence or absence of pain at the time of CT, high-attenuating crescent, and aneurysm complication.

Results: Sensitivity of the high-attenuating crescent sign as an indication of complicated aneurysm was 77%; specificity, 93%; and positive predictive value, 53%. The sign showed a statistically significant correlation with large aneurysm size (P < .001) and presence of pain at the time of CT (P < .003).

Conclusion: In patients without CT evidence of frank aneurysm leak, the high-attenuating crescent sign should be regarded as a sign of impending AAA rupture, particularly in patients with pain.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Aorta, Abdominal / diagnostic imaging
  • Aortic Aneurysm, Abdominal / diagnostic imaging*
  • Aortic Rupture / diagnostic imaging*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Tomography, X-Ray Computed*