Aortoenteric Fistula through a Thrombosed Graft

Background

Secondary aortoenteric fistula can develop after any aortic reconstruction via a connection between the repaired aorta and any part of the gastrointestinal tract. It can happen after both open and endovascular repair with an incidence rate of up to 4% [1,2]. Thrombotic occlusion of the aortic graft is a known complication that can necessitate an extra-anatomical bypass to establish distal perfusion [3,4]. It has not been previously reported, and one would not expect a fistula to form between a thrombosed graft and the gastrointestinal tract. In this case report, we describe an aortoenteric fistula in an elderly male through a thrombosed aorta-iliac bypass graft, his treatment, and his hospital course. The patient consented to publication of his case information.

Case Report

A 75-year-old male with a history of abdominal aortic aneurysm and right axillary-bifemoral bypass (for 10 years) after thrombosis of an aortoiliac bypass was transferred to our institution with hematochezia and a concern for aortoenteric fistula (Figure 1). His problem was initiated as persistent melena 2 months prior to his current admission. At that time, esophagogastroduodenoscopy (EGD) had shown bleeding and clots at the fourth segment of the duodenum (D4) for which a clip had been placed for what endoscopically appeared as a large Dieulafoy’s lesion (Figure 2A, 2B). The patient symptoms persisted, and he underwent a second EGD 1 month later that identified a large clot on top of the previously placed Endoclip.

After transfer to our institution, the patient underwent a computed tomography scan with intravenous contrast which revealed contrast extravasation into the duodenum and effacement of the soft tissue between the thrombosed aortic graft and D4 (Figure 3A, 3B). With a presumed diagnosis of an aortoduodenal fistula, the patient underwent exploratory laparotomy with extensive lysis of adhesions secondary to his previous abdominal surgeries. The fourth portion of the duodenum was adherent to the old Dacron graft where the aortoenteric fistula was identified (Figure 4). The main body of the previous Dacron aortoiliac graft was excised down to bilateral iliac limbs with oversewing of native infra-renal aorta and distal iliac limbs. The previously placed Endoclip was identified at the site of fistula and the duodenotomy was repaired in 2 layers. We then performed pyloric exclusion and created a retrocolic loop gastrojejunostomy. An omental flap was performed to buttress the proximal aortic stump. The patient was successfully extubated and taken to the intensive care unit. After a prolonged hospital course, the patient was discharged in stable condition on postoperative day 24 following the index operation.

Discussion

Aortoenteric fistula is the deadliest complication after an abdominal aortic aneurysm repair with mortality rates reaching 50% even in most experienced hands and at high-volume centers [5]. Since a fistula through a thrombosed graft has not been previously described, any comparison would be limited to existing literature on aortoenteric fistula through a patent graft. Explantation of the graft and an extra-anatomical bypass has traditionally been the treatment of choice. Our patient had an existing right axillary-bifemoral bypass secondary to his thrombosed aortoiliac bypass graft and only required graft explantation and bowel repair. As this is solely a case report, discussion about the mechanism of fistula formation through the thrombosed graft would be speculative; though a likely explanation would be continued movement of the graft with each cardiac cycle which ultimately lead to fistula formation.

A study by Grande et al. conducted 28 autopsies on aortoenteric fistula patients and found that the majority of patients (23 patients) had died from exsanguination [6]. The majority of patients had a Dacron graft (12 out of 16 patients) and the majority of fistulas (94%) had developed near the proximal anastomosis with the duodenum being the most common enteric site of fistula development [6]. A later study following 42 patients found a mortality rate of 58% with the most common cause being blow out of the aortic stump [7]. Recurrence of the fistula was found in 16 out of 34 patients who survived surgery, and at the 12-month follow-up, only 7 patients were still alive [7].

In the study by Batt et al. [5], 37 aortoenteric fistula patients were followed with a mean of 41 months follow-up. More than half of these patients had an acute presentation and more than 70% of patient had a form of hemorrhage. In this cohort, extra-anatomical reconstruction was performed only in 24% of the patients. They reported a 30-day mortality rate of 43% with age >75 years being the sole predictive factor of mortality [5]. Our patient met this age criteria for significantly increased peri-operative mortality. They also reported the peri-operative complication rate of 59% and the mean hospitalization of 20 days, which was similar to our patient experience.

More favorable outcomes had been reported with endovascular repair in a study comparing endovascular versus open repair of the aortoenteric fistulas [8]. Kakkos et al. followed 25 patients with aortoenteric fistula among which 8 patients were treated with endovascular repair and 12 patients were treated with open repair [8]. Morbidity was significantly higher with open repair (77% versus 25%) with no mortality in the endovascular group. The early survival benefit in the endovascular group later faded away since the 2 groups were not different in the long-term survival at 2 years [8]. Kakkos et al. [8] found that the worse outcome was only associated with the number of symptoms at presentation. Apparently, our patient did not have an endovascular repair option.

In another study investigating the optimal method of enteric repair, significantly higher rates of fistula recurrence were reported with simple repair as opposed to diversion or resection [9]. We repaired the duodenotomy in 2 layers and performed pyloric exclusion with retrocolic loop gastrojejunostomy. Our patient did not have any local recurrence at the site of the aortoenteric fistula through his course. The aforementioned study also found that omental interposition was associated with lower mortality independent from the repair technique [9]. We had interposed the omentum at the duodenotomy, gastrojejunostomy, and the proximal and distal over-sewn ends of the resected graft.

Conclusions

An aortoenteric fistula can form through a thrombosed graft. Since this is not an expected route of fistula formation, there may be a delay in identification. Work-up and treatment modality would not be different from an aortoenteric fistula through a patent graft, and as in the presented case, it may still have significant morbidity and a prolonged hospitalization.