Atherosclerotic abdominal aortic aneurysms: Comparative data of different types based on the degree of inflammatory reaction.

Two-hundred two patients who consecutively underwent histological examination of the aneurysm wall with the full thickness at the time of repair procedure of infrarenal true abdominal aortic aneurysm were retrieved from the files of the Department of Pathology at the National Cardiovascular Center in the 13-year period from September 1977 to August 1990. Inflammatory aneurysms were present in 15 patients (7.4%);14 men, 1 woman. The other 187 patients with ordinary atherosclerotic aneurysms were classified into four groups according to the thickness of adventitia and periadventitia, and clinical and pathological variables were compared between these groups and patients with inflammatory aneurysms. Patients with inflammatory aneurysms were significantly more likely to be younger and demonstrate weight loss, ureteric obstruction, absence of abdominal bruit, more accelerated erythrocyte sedimentation rate, and more thickening of adventitial and periadventitial tissue. The microscopic features of ordinary atherosclerotic aneurysms that had remarkable thickening of adventitia and periadventitia showed no sharp distinction from those of inflammatory aneurysms. Our study suggests that atherosclerosis plays a major role in the aneurysmal dilatation of the aorta and in the periaortic inflammatory process, and that inflammatory aneurysms are located at one end of the spectrum of atherosclerotic abdominal aortic aneurysms.