Natural history and CT appearances of aortic intramural hematoma.

Rupture of the vasa vasorum into the media of the aortic wall results in an aortic intramural hematoma. Characteristic findings of an aortic intramural hematoma include a crescentic hyperattenuating fluid collection at unenhanced computed tomography (CT) and a smooth, nonenhancing, thickened aortic wall at contrast material-enhanced CT. The CT appearance of untreated intramural hematomas evolves over time, and decreased attenuation is a clue to the chronicity of a hematoma. CT is particularly useful for evaluating aortic intramural hematomas because it allows their differentiation from aortic dissections, which have similar clinical manifestations, and permits an exact determination of their location-crucial information for surgical planning. On the basis of CT findings, some hematomas may be expected to resolve spontaneously, whereas others may be identified as posing a high risk for serious complications such as aortic dissection, aneurysm, and rupture. Appropriate clinical management is aided by accurate recognition of diagnostically specific CT features and awareness of their significance.