Imaging Sign in Diagnostic Radiology

Hyperattenuating Crescent Sign : is a CT sign of acute or impending rupture of abdominal aortic aneurysm.

Finding : A well-defined peripheral crescent of increased attenuation within the thrombus of a large abdominal aortic aneurysm.

This finding is best appreciated on unenhanced CT images. It represents an internal dissection of blood into either the peripheral thrombus or the aneurysm wall, a process that either causes or results from a loss in the ability of the thrombus to protect the aneurysm from rupture. It is one of the earliest and most specific imaging manifestations of the rupture process

Reference : Radiographics l Radiology