CT of aortic aneurysms: the distinction between mural and thrombus calcification

Aortic calcification, either mural or thrombus, is a common finding in patients with abdominal aortic aneurysms. Differentiating between the two sites of calcification is necessary in order to avoid confusing simple thrombus calcification with displaced calcified intima in aortic dissection. The CT scans of 145 cases of abdominal aortic aneurysm and seven cases of abdominal aortic aneurysm with dissection were analyzed with respect to the location of the calcification: mural only or mural and thrombus. Mural calcification was seen in all 152 patients with aneurysms whereas thrombus calcification was identified in only 33 (24%) of the 136 patients with thrombus. Displaced intimal calcification caused by aortic dissection can either appear similar to or, at times, be indistinguishable from thrombus calcification. Thrombus calcification was present in four (57%) of the seven patients with abdominal aortic aneurysms and dissection. To avoid the possibility of a false-positive diagnosis of aortic dissection in patients with abdominal aortic aneurysm, other signs of aortic dissection should be sought such as separation of the true and false lumina by an intimal flap.