INTRODUCTION
An aortoenteric fistula (AEF) is defined as an abnormal connection between the aorta and the gastrointestinal tract. A primary AEF (PAEF) arises de novo between the aorta and the gastrointestinal tract. By contrast, a secondary AEF (SAEF) involves erosion of a surgically placed aortic graft into the gastrointestinal tract. Although AEFs are rare, with the incidence of SAEF ranging from 0.36% to 1.6%,1,2 they carry an exceedingly high risk of mortality. The most common presentation of an AEF is gastrointestinal bleeding. In this report, we discuss an atypical presentation of a SAEF in the absence of bleeding.
CASE REPORT
A 64-year-old man with a history of peripheral arterial disease status post aortobifemoral bypass (2017) and right femoral-popliteal bypass with a polytetrafluoroethylene (PTFE) graft and carotid stenosis status post right carotid endarterectomy presented to the hospital with diffuse abdominal pain. He additionally reported obstipation for 1 week. He denied hematemesis, hematochezia, or melena. On presentation, the patient was tachycardic to 102 bpm and hypertensive to 187/86 mm Hg. Laboratory studies were remarkable for a leukocytosis to 21 K/μL and a stable hemoglobin of 13.5 g/dL. Chemistries, including liver function panel, were within normal limits. Abdominal and pelvic computed tomography (CT) angiography showed a new heterogeneous soft tissue and complex fluid about the distal aorta measuring approximately 5.7 × 3.2 × 6.2 cm, with air in the region extending into the occluded distal aorta and left limb of the aortofemoral bypass (Figures 1 and 2).
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Figure 1.: Axial computed tomography angiography image showing the air and fluid collection (yellow arrows) and the adjacent loop of the bowel (orange arrow).
Figure 2.: Sagittal computed tomography angiography image showing the fluid collection with a focus of air (yellow arrows) and thrombosed left aortofemoral bypass (orange arrow).
Given the concerning, yet inconclusive, imaging results, the gastroenterology service was consulted for further evaluation and management. The gastroenterology team further discussed the inconclusive imaging findings with radiology and chose to proceed with an esophagogastroduodenoscopy (EGD). EGD showed a 1.5 cm nonbleeding ulcer with adherent clot in the third portion of the duodenum (Figures 3 and 4) with an otherwise normal-appearing esophagus, stomach, duodenum, and jejunum. This was highly suspicious for AEF because peptic ulcers are typically not found in the third portion of the duodenum.
Figure 3.: 1.5 cm nonbleeding ulcer with adherent clot in the third portion of the duodenum.
Figure 4.: An additional view of the 1.5 cm nonbleeding ulcer with adherent clot.
The patient remained hemodynamically stable and underwent surgery, in which an aortoduodenal fistula was confirmed. The surgery consisted of explant of the infected Dacron graft with frank pus noted, right axillary-to-right femoral bypass with a PTFE graft, primary closure of a 2–3 cm duodenal defect, and gastrostomy-jejunostomy tube placement. Intraoperative cultures sent from the abscess surrounding the left limb of the aortofemoral bypass grew the Enterobacter cloacae complex and C. albicans. Treatment of his polymicrobial aortic endovascular graft infection was completed with 6 weeks of intravenous ertapenem and oral fluconazole daily. An interval CT scan showed no evidence of duodenal leak. After approximately 1 month of hospitalization, the patient was successfully discharged to subacute rehabilitation. Unfortunately, he was readmitted to the hospital 2 weeks later with right lower extremity critical limb ischemia. He had an occluded right axillary-to-femoral bypass graft and underwent right through-the-knee amputation with endovascular thrombectomy of the axillary graft and stenting of the profunda. Shortly after surgery, there was rupture of a presumed pseudoaneurysm in the right lower quadrant and he was taken back to the operating room for a hematoma evacuation. Given his poor prognosis, his family decided to pursue comfort care and he died.
DISCUSSION
This case depicts a unique presentation of an AEF. While most of the AEFs present with gastrointestinal bleeding, our patient presented with abdominal pain only. One review found that among patients with infected grafts, 36% of the patients with SAEFs had no gastrointestinal bleeding on presentation.3 It is believed that bleeding does not occur in these cases because there is no true communication between the lumen of the prosthesis and the involved bowel.4 If no gastrointestinal bleeding is present in these patients, routine evaluation may miss the diagnosis of AEF. Several studies that looked at patients presenting with gastrointestinal bleeding have found that the sensitivity for the diagnosis of SAEFs by endoscopy is approximately 25%5–7 and the sensitivity of using CT for SAEF diagnosis ranges from 45% to 93%.8,9 Given the lower sensitivity, endoscopy is less often used as a modality for the diagnosis of an AEF. As seen in our unique case, clinicians should consider CT angiography and endoscopy even in the absence of clinical gastrointestinal bleeding in patients with a significant history of vascular grafts, especially if there is concern for an infected graft, because this is a major risk factor of SAEF. There have been few studies performed to determine whether there is increased risk of SAEFs based on the type of surgical approach, aortic anastomotic reconstruction, or graft material used.8,10 These studies showed a higher occurrence of SAEFs after aortobifemoral bypasses when compared with aortobiiliac or aortic tube grafts, end-to-side anastomosis compared with end-to-end, and the use of Dacron grafts compared with PTFE.
Duodenal ulcers are typically found in the duodenal bulb, and the second most common location is the second portion of the duodenum.11 If ulcers are found deeper in the duodenum or remainder of the small bowel, clinicians should consider other etiologies, such as AEFs, rather than typical causes of peptic ulcer disease. Previous studies have shown that most of the primary AEFs are located in the third and fourth portions of the duodenum because these are anatomically the closest to the aorta.4 These portions of the duodenum are not routinely checked during a normal EGD. If an AEF is suspected, as in our case, a push enteroscopy with a pediatric colonoscope should be attempted. The management of an AEF typically involves antimicrobial therapy and surgical repair. The use of endoscopy can only assist with establishing a diagnosis. The mortality in patients with an AEF is nearly 100% without surgery. Unfortunately, there is still high mortality (50%–60%) even after surgical repair.5
This case highlights the importance of maintaining a high index of suspicion for an AEF in a patient presenting with abdominal pain and leukocytosis with a history of aortofemoral bypass surgery.
DISCLOSURES
Author contributions: K. Panagos is the article guarantor, performed the literature review, and wrote the manuscript. B. Ji assisted with gathering objective data and chart review. J. Clinton, A. Canakis, and L. George reviewed and edited the manuscript.
Financial disclosure: None to report.
Informed consent was obtained for this case report.
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