The high attenuating crescent sign represents an acute hematoma within either the mural thrombus or the aneurysm wall, especially when detected on unenhanced CT scans. It is a specific sign of impending abdominal aortic aneurysm (AAA) rupture or so-called contained rupture.
The hyperattenuation is caused by fresh blood that first insinuates itself into the mural thrombus and later penetrates the aortic wall. Thus, the pathophysiology is not similar to that of an intramural hematoma, in which hemorrhage occurs from within the aortic wall.
The sensitivity of the high-attenuating crescent sign as an indication of a complicated aneurysm is 77%; specificity, 93%; and positive predictive value of 53%.
Treatment and prognosis
When seeing this sign in an aneurysm, especially in patients with pain, it is warranted to inform the referring physician or surgeon about the high risk for aneurysmal rupture, even if there are no primary or frank signs of leakage. This condition may require emergent surgical management and warrants close vitals monitoring.
- 1. Mehard WB, Heiken JP, Sicard GA. High-attenuating crescent in abdominal aortic aneurysm wall at CT: a sign of acute or impending rupture. Radiology. 1994;192 (2): 359-62. Radiology (abstract) - Pubmed citation
- 2. Chao CP, Walker TG, Kalva SP. Natural history and CT appearances of aortic intramural hematoma. Radiographics. 29 (3): 791-804. doi:10.1148/rg.293085122 - Pubmed citation
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