Infected aneurysms of the infrarenal abdominal aorta: diagnostic criteria and therapeutic strategy.

From 1976 to 1994 we performed surgical treatment of 18 infected aneurysms of the infrarenal abdominal aorta. The aneurysm had ruptured in nine patients: into the retroperitoneum in six patients, and into an adjacent structure in three patients (duodenum, inferior vena cava, left renal vein). Two patients had an associated spondylitis. Four patients were in shock at the time of surgical treatment. Six patients (including four patients with Salmonella infection and two patients with spondylitis) had positive preoperative blood cultures. Salmonella was the most common microorganism (27%). Anaerobes accounted for 16%. In situ replacement was performed in 13 patients including three procedures performed under emergency conditions with frank purulent infection. Extraanatomic bypass was performed in five patients. Early postoperative death occurred in two patients (11%) due to septic complications (rupture of aortic anastomosis in one patient and rupture of aortic stump in one patient). All surviving patients underwent prolonged antibiotic therapy for at least 6 weeks. Overall mortality secondary to infected aneurysm was 16%. Infection of the aortic graft occurred in four patients (38%) including two patients with Salmonella infection and one patient with spondylitis. One patient developed a false anastomotic aneurysm 6 months postoperatively and was treated by in situ arterial allograft replacement. Postoperative blood cultures were positive in two patients presenting spondylitis and infection of the aortic prosthesis occurred in one of these patients. In addition to rupture, poor prognostic factors included spondylitis and Salmonella infection that were found to greatly enhance the risk of postoperative graft infection following in situ reconstruction.