Mycotic aneurysms of the thoracic and abdominal aorta and iliac arteries: experience with anatomic and extra-anatomic repair in 33 cases

Abstract

Objective: A mycotic aneurysm of the aorta and adjacent arteries is a dreadful condition, threatening life, organs, and limbs. With regard to the aortic segment involved, repair by either in situ replacement or extra-anatomic reconstruction can be quite challenging. Even when surgery has been successful, the prognosis is described as very poor because of the weakened health status of the patient who has developed this type of aneurysm. The aim of our study was to find out whether any progress could be achieved in a single center over a long time period (18 years) through use of surgical techniques and antiseptic adjuncts.

Material and methods: From January 1983 to December 1999, a total of 2520 patients with aneurysms of the thoracic and abdominal aorta and iliac arteries underwent surgery for aortic or iliac replacement at our institution. During that period, 33 (1.31%) of these patients (mean age, 64.3 years) were treated for mycotic aneurysms of the lower descending and thoracoabdominal (n = 13), suprarenal (n = 4), and infrarenal (n = 10) aorta and iliac arteries (n = 6). Twenty (61%) of these 33 patients had histories of various septic diseases; in the other 13 (39%), the etiology remained uncertain. Preoperative signs of infection, such as leukocytosis and elevated C-reactive protein, were found in 79% of the patients, and fever was apparent in 48%; 76% of the patients complained of pain. At the time of surgery, eight (24%) mycotic aneurysms were already ruptured, and 20 (61%) had penetrated into the periaortic tissues, forming a contained rupture. Five (15%) aneurysms were completely intact. The predominant microorganisms found in the aneurysm sac were Staphylococcus aureus and Salmonella species. Careful debridement of all infected tissue was essential. In the infrarenal aortic and iliac vascular bed, in situ reconstruction was performed only in cases of anticipated "low-grade" infection. Alternative revascularization with extra-anatomic procedures (axillobifemoral or femorofemoral crossover bypass graft) was carried out in eight of 16 cases. All four suprarenal and all 13 mycotic aneurysms of the thoracoabdominal aortic segment were repaired in situ. Antibiotics were administered perioperatively, and all patients were subsequently treated with long-term antibiotics.

Results: In-hospital mortality was 36% (n = 12). Because of the smallness and heterogeneity of the sample, we could not demonstrate significant evidence for any influence of aneurysm location or type of reconstruction on patients' outcome. However, survival was clearly influenced by the status of rupture. During long-term follow-up (mean, 30 months; range, 1-139 months), 10 patients (48%) died-one (4.8%) probably as a consequence of the mycotic aneurysm, the others for unrelated reasons. Eleven patients (52%) are alive and well today, with no signs of persistent or recurrent infection.

Conclusions: A mycotic aneurysm of the aortic iliac region remains a life-threatening condition, especially if the aneurysm has already ruptured by the time of surgery. Although the content of the aneurysm sac is considered septic, as was proved by positive cultures in 85% of our patients, in situ reconstruction is feasible and, surprisingly, was not more closely related to higher morbidity and mortality in our series than ligation and extra-anatomic reconstruction, although most of the aneurysms repaired in situ were located at the suprarenal and thoracoabdominal aorta. We assume that our operative mortality rate of 36%, which relates to a rupture rate of 85%, could be substantially lowered if the diagnosis of mycotic aneurysm were established before rupture.