Surgical pathology of infected aneurysms of the descending thoracic and abdominal aorta: clinicopathologic correlations in 29 cases (1976 to 1999).

Infected aortic aneurysms are uncommon, and only rarely have their surgical pathological features been described. Clinical and histopathologic features were evaluated in patients undergoing surgical repair of infected aneurysms of the descending thoracic or abdominal aorta over a 24-year period. Findings were compared with observations (primarily from autopsy studies) from the previous 25-year period (1950 to 1975) and other more recent reports. Of the 29 patients in our study, 79% were men, 90% had risk factors for atherosclerosis, and 72% had an identifiable risk or source of infection. Fever was present in 76%, and abdominal or back pain was seen in 66%. Among the 20 cases with an identifiable causative organism, staphylococcus accounted for 30%, streptococcus for 20%, salmonella for 20%, Escherichia coli for 15%, and other organisms for 15%. Aneurysms were saccular in 59% and infrarenal in 42%, and had a mean diameter of 5.6 cm. Microscopically, 6 patterns were recognized: acute inflammation superimposed on severe chronic atherosclerosis (55%), atherosclerosis with chronic inflammation (20%), acute inflammation without atherosclerosis (7%), chronic adventitial inflammation (7%), pseudoaneurysm formation (7%), and necrotizing granulomatous inflammation (4%). Special stains for organisms were positive in only 38% of the cases. Pathological findings of this series of surgical specimens spanning the fourth quarter of the twentieth century were not appreciably different from those described in autopsy series from the preceding years, although the causative microorganisms and agents used to treat them, preoperative diagnostic modalities, and surgical approaches have evolved.