Abstract
Mycotic aortic aneurysms are an uncommon yet still life-threatening pathology. We report on a 67-year-old male who had a persistent fever and back pain. Contrast enhanced computed tomography (CT) showed multiple aortic aneurysms located in the aortic arch, the descending thoracic aorta and the supraceliac abdominal aorta. After 2 months of antibiotic therapy, a staged operation was carried out with 2-week interval, which includes a graft replacement of aortic arch with elephant trunk technique and a graft replacement of thoraco-abdominal aorta with omental transfer. The postoperative course was uneventful. This case seems to be quite rare in terms of multiplicity and location of mycotic aneurysms. Surgical strategy for this pathology is discussed.
1 Introduction
Multiple mycotic aneurysms are infrequent disease, and often result in a catastrophic outcome unless an appropriate treatment is performed. Surgical intervention remains a challenging task in terms of causative organisms, the timing of operation, operative techniques, prosthetic materials used, and adjuvant antibiotic chemotherapy. We present a case of multilocular mycotic arch-thoraco-abdominal aortic aneurysms, who underwent a successful staged graft replacement of aortic arch and thoraco-abdominal aorta.
2 Case report
A 67-year-old man was referred to our department under the diagnosis of abdominal aortic aneurysm on 12th December 1997. He had had a persistent high fever and a low back pain for 6 weeks since the beginning of November 1997. Mycotic aneurysm was highly suspected from his clinical history and the initial computed tomographic (CT) scan which demonstrated a dumbbell-shaped aneurysm of the supraceliac abdominal aorta.
On admission day, a repeat CT scan of both thorax and abdomen was performed, and multiple aortic aneurysms were also found in thoracic aorta (Fig. 1) . C-reactive protein concentration was 22 mg/dl. Serologic reaction for syphilis was negative. An aggressive medical treatment such as antibiotic chemotherapy and lowering blood pressure was initiated. Although frequent blood cultures were performed, a specific organism had never been detected. The infection was well controlled, however, a gradual increase in size of the aneurysms was observed by serial follow-up CT scans over 8 weeks. As a consequence, we planned a staged operation for these aneurysms.
A, three-dimensional CT scan demonstrates aneurysms (arrow) in aortic arch and proximal descending aorta. B, contrast enhanced CT scan shows an irregular aortic lumen with a periaortic soft tissue mass (arrow) in thoraco-abdominal aorta.
The first operation was performed in February, 1998 via a median sternotomy. The aortic arch including aneurysms was completely resected and replaced with a Hemashield (Meadox Medicals, Inc.) 24 mm Dacron woven arch graft using an elephant trunk technique under cardiopulmonary bypass (CPB) with selective cerebral perfusion. Two weeks later the second operation was performed via a left posterolateral thoracotomy. The en-bloc resection of the residual aneurysms of the thoraco-abdominal aorta was performed, and the aorta was replaced between the elephant trunk and the level just proximal to branching of a celiac artery using a Hemashield 22 mm Dacron woven graft under mild hypothermic femoro-femoral CPB. Cerebrospinal fluid drainage and naloxone (1 μg/kg per h) were used in addition to segmental repair technique as adjuncts to reduce the risk of paraplegia. The intercostal arteries could not be reconstructed because of their fragility resulted from inflammatory degeneration. The graft was covered with an omental flap as much as possible to include the distal suture line.
His postoperative course was uneventful except for a chylothorax that was controlled by a conservative therapy. The postoperative CT scans demonstrated excellent result of graft replacement of aortic arch and thoraco-abdominal aorta (Fig. 2) . He remains well without recurrent graft infection after follow up of 15 months. The pathohistological and bacteriological examination of the specimens such as aortic wall and aneurysms obtained from both operations showed accumulation of lymphocytes and plasma cells in the adventitia, which suggested non-specific inflammatory process.
Postoperative three-dimensional CT scan demonstrates the replaced graft of aortic arch and thoraco-abdominal aorta.
3 Discussion
Clinical symptoms of the mycotic aneurysms are frequently non-specific during the early stages [1]. A number of cases present fever of unknown origin with some non-specific thoraco-abdominal pain, as is in the present case. Positive blood cultures were found in 50–70% of patients [2]. Although a specific organism had never been identified by frequent blood cultures in the present case, we confirmed the diagnosis from both the clinical feature of sepsis and the typical findings obtained by CT scans, which included multiple dumbbell-shaped aneurysms with a periaortic soft tissue density [3]. Other possibilities of vasculitis such as syphilitic processes, Behςet syndrome, and Horton disease could be denied by their characteristic clinical features and pathohistological examinations.
The optimal methods to treat the mycotic aneurysms, i.e. the timing of operation, operative techniques, the duration of antibiotic chemotherapy are not well established and remain controversial [1,2]. As concerns the timing of operation it might be generally accepted that operation should be performed after the establishment of effective antibiotic therapy. Recently, Chiba et al. reported that urgent operation during uncontrolled sepsis resulted in a high mortality rate of 80% compared with that of 14% in patients who underwent operation after resolution of their active infection [4]. Fortunately in our case, an intensive antibiotic therapy was quite effective and prevented a periaortic extension and rupture. However, a gradual increase in size of aneurysms was observed by serial follow-up CT scans, so that a planned operation was carried out.
En bloc excision of both the aneurysm and the perianeurysmal infected tissue and in situ prosthetic graft replacement is the basic principle of operation for thoraco-abdominal mycotic aneurysm [5]. Although a single stage procedure is the ideal, the present case was so malnourished due to prolonged illness that we decided to perform a two-stage procedure. The single stage graft replacement of aortic arch and thoraco-abdominal aorta was not considered as an appropriate surgical strategy because of the substantial risk of mortality and morbidity.
Recently, in situ insertion of an aortic conduit homograft for mycotic aneurysms has been reported to be a useful method that reduces the late postoperative infection rate [6,7]. However, the cryopreserved homograft has not been widely used yet in Japan and it is difficult to obtain the graft. So that we used the woven Dacron graft that was immersed in antibiotic solution, and covered the thoraco-abdominal segment of the graft with omental flap. There are no definite recommendations for the duration of postoperative antibiotic chemotherapy, but a minimum of 6 weeks has been suggested.
In conclusion, once the diagnosis was made for infected aortic aneurysms, an intensive medical treatment should be recommended to prevent rupture. Simultaneously a surgical strategy including in situ graft replacement should be planned.
The authors are grateful to Dr A. Tsukino of the Department of Plastic Surgery and Dr H. Miyake of the Department of Anesthesiology for their help.
