HIGH-ATTENUATING CRESCENT IN ABDOMINAL AORTIC-ANEURYSM WALL AT CT - ASIGN OF ACUTE OR IMPENDING RUPTURE

PURPOSE: To determine whether a peripheral high-attenuating crescent i n an abdominal aortic aneurysm (AAA) on unenhanced computed tomographi c (CT) scans is a sign of impending or active aneurysm rupture. MATERL ALS AND METHODS: CT scans were reviewed of 149 consecutive patients op erated 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 indic ation of complicated aneurysm was 77%; specificity, 93%; and positive predictive value, 53%. The sign showed a statistically significant cor relation with large aneurysm size (P <.001) and presence of pain at th e time of CT (P <.003). CONCLUSION: In patients without CT evidence of frank aneurysm leak, the high-attenuating crescent sign should be reg arded as a sign of impending AAA rupture, particularly in patients wit h pain.