Endovascular treatment of a tuberculous aneurysm of the pararenal abdominal aorta leading to an aortoduodenal fistula

This case report describes the presentation of a 79-year-old woman with no significant past medical history diagnosed with a saccular aneurysm with an aortoduodenal fistula. An emergency endovascular aneurysm repair was performed. Although the postoperative course was uneventful, 10 months after endovascular aneurysm repair, the patient died of miliary tuberculosis from mycotic aneurysms. Mycotic aneurysms are uncommon, and mycotic aneurysms caused by Mycobacterium tuberculosis are even rarer. Therefore, we believe our study makes a significant contribution to the literature given the rarity of the condition and suggests the importance of maintaining a high index of suspicion for tuberculosis as a possible cause of aortoduodenal fistula in primary mycotic aneurysm.


CASE REPORT
A 79-year-old woman without a significant past medical history (including any previous history of infections) was admitted to our emergency department with massive melena and hemorrhagic shock. The patient was afebrile and suffered from se-  and histological findings were suggestive of tuberculous inflammation of the thrombosed aneurysm leading to right renal miliary tuberculosis (Fig 4). The family members of the patient agreed to allow us to publish her case details and images.

DISCUSSION
In the present case, we performed an emergency EVAR for a saccular aneurysm at the origin of the right renal artery with an aortoduodenal fistula, which caused hypovolemia and hemorrhagic shock. Pathological autopsy revealed accumulation of Mycobacterium tuberculosis in the cystic mass, which thrombosed and showed a tendency to shrink on the follow-up CT scans, leading to the diagnosis of a tuberculous mass. Infectious aortic aneurysms are reported 1-5 to account for approximately 3% of all aortic aneurysms, and infectious aortic aneurysms caused by M tuberculosis are extremely rare. According to the report by Volini et al, 6 there are two possible mechanisms for the development of tuberculous aortic aneurysms: (1) a direct invasion of the aortic wall from a tuberculous lesion such as in a lymph node or bone and an abscess around the aorta or (2) hematogenous spillover into the aortic feeding vessels or damaged aortic intima. It has been reported that more than 90% of the tuberculous infected masses have a saccular shape. 5,7 In this case, the pathogenesis of the cystic mass was not clear because a prior infection was unknown, and the mass developed naturally in a healthy patient with no history of tuberculosis.
Although the patient was asymptomatic, the pathological autopsy findings revealed a lesion in the cystic mass caused by M tuberculosis that was not eradicated despite the mass undergoing thrombosis by stent grafting with the subsequent stopping of the bleeding. We expected that the chronic infection had rapidly progressed to miliary tuberculosis. Despite the increase in endovascular treatment in recent years, it must be chosen based on the urgency and the patient's surgical tolerance. However, the cause of the infection may not be identified. Although there have been reports of good results with endovascular treatment of tuberculous aortic aneurysms, 1-4 the importance of antituberculosis drugs after an endovascular treatment has been highlighted. As for the surgical technique, in this case, reconstruction of the right and left renal arteries was performed using VIABAHN (covered stent) and a bare metal stent, in addition to the usual abdominal aortic stent graft. In recent years, there have been reports on the usefulness of the chimney and the sandwich techniques using covered stents and bare stents for pararenal aneurysms. 8-10 Therefore, we believed that a right renal artery reconstruction with a covered stent was the only option for this saccular aneurysm at the origin of the right renal artery.
The operative time was short (61 minutes), and no endoleak was observed immediately after the operation. The progression of anemia owing to gastrointestinal bleeding had subsided, and thrombosis and reduction of the cystic mass were observed at an early stage. Therefore, we believed that this surgical technique was appropriate. Because aortoduodenal fistula had developed, the risk of postoperative stent graft infection was high, and thorough antibiotic therapy was considered essential and was administered in this patient. However, this strategy did not lead to a cure, the diagnosis was not confirmed until the patient's condition progressed to miliary tuberculosis, and she died. We regret that we missed the timing of the open surgery and did not reach a definitive diagnosis as the patient's progress after the endovascular treatment was good. As a future issue, there is the possibility that the cause of the aortic saccular aneurysm is a tuberculous infected aneurysm, although this is very rare. If a tuberculous infected aneurysm is suspected, postoperative antituberculosis therapy is imperative, even if the endovascular treatment is successful.

CONCLUSIONS
In this study, we encountered a case of miliary tuberculosis 10 months after the operation, although the patient was brought to the emergency room with hemorrhagic shock owing to an aortoduodenal fistula and was saved by emergency EVAR. Pathological autopsy revealed a tuberculous, infected mass. Considering the possibility of tuberculosis as a cause of asymptomatic stent graft treatment of saccular masses and to consider preoperative examination, selection of antibiotics, and postoperative therapy including antituberculosis drugs is necessary in some cases.  Postoperative enhanced three-dimensional computed tomography CT (3D-CT) scan. The 3D-CT scan showed that there was no endoleak and the bilateral renal artery were preserved. After the Viabahn stent was deployed in the right renal artery, the Excluder Cuff and Endurant Cuff were inserted just below the superior mesenteric artery. Finally, a SMART STENT was deployed in the left renal artery.