Abstract: Introduction: Aorto-enteric fistula (AEF) is defined as a communication between the aorta and the gastrointestinal (GI) tract. AEF is either primary or secondary. Primary AEF is a communication between the aorta and the GI tract due to one of a long list of diseases, while secondary AEF is created after the erosion of an aortic prosthetic graft into the surrounding GI structures. Until recently, the accepted method of AEF treatment was open repair. Endovascular repair is currently considered a very promising approach as a bridging therapy before open repair. According to some authors, the endovascular approach can be used as a definitive therapy. The aim of this study is to examine whether endovascular AEF repair (eAEFr) is a safe, definitive treatment.
Materials & Methods: An extensive search in the PubMed indexing system was conducted by the authors, using a number of keywords in all relevant and various combinations. The literature search was limited by time period and by English language.
Results:Thirty studies were included, reporting on 105 patients (majority male) with a median age of 73 years. The most affected part of the gastrointestinal tract (GI) was the duodenum (16.2%). Secondary AEF was more common (57.1%), and GI bleeding was the most common presenting symptom (89.5%). Fifty patients (47.6%) received a definitive endovascular AEF repair (eAEFr), 15 (14.3%) received eAEFr as a bridging method, and 40 patients underwent open AEF repair (38.1%). The median follow-up period was 14.1 months, and the most common complication was recurrent AEF (9.5%). Eighteen patients (17.1%) had a reintervention and the eAEFr group had a significantly higher reintervention rate. Mortality between the two groups was similar.
Discussion: eAEFr and open AEF repair have similar complications and mortality rates, but eAEFr demonstrates higher reintervention rates. As a bridging method, eAEFr has already demonstrated its promising results, but as a definitive therapy for AEF it should be considered only in cases where sepsis or systemic infection are not present. Patients undergoing eAEFr as their final therapy should remain under rigorous follow-up for infection or bleeding. Future studies should focus on the role of eAEFr in subgroups of patients and recognize which subgroup would benefit from eAEFr as a definitive therapy.
Key words: aorto-enteric fistula, endovascular repair, sepsis, graft infection
Aorto-enteric fistula (AEF) is defined as a communication between the aorta and the gastrointestinal (GI) tract. AEF is either primary or secondary.1 Primary AEF is a communication between the aorta and the GI tract due to one of a long list of diseases, while secondary AEF is created after the erosion of an aortic prosthetic graft into the surrounding GI structures.
Primary AEF mainly originates from atherosclerotic, traumatic, or mycotic aneurysms, and is a result of de novo pathological connections between the aorta and the GI tract. Some frequent causes for AEF are radiation, infections, neoplasms, untreated aneurysms, peptic ulcers, inflammatory bowel disease, perforating biliary stones, and ingestion of foreign bodies.2 In 83% of cases, AEF occurs between the infrarenal aorta and the third or fourth portion of the duodenum.1 In one-fifth of primary AEF cases, the small bowel or the colon are involved, while the stomach or other GI locations are involved in only 5% of the cases.1
Secondary AEF is a communication between a synthetic graft and the GI tract, after previous open repair of aortic aneurysms. The most frequently affected site of GI tract is the third portion of the duodenum, which results from its retroperitoneal fixation and proximity to the aorta that causes ischemia and, consequently, necrosis of the intestinal wall. Post-endovascular aneurysm repair (EVAR) secondary AEF exist, but occur less frequently than AEF after open aortic repair.
The first mention of primary AEF in the literature was from Cooper in 1829, the first reported case of a secondary AEF was published in 1953 by Brock, and the first repairs of primary and secondary AEF were performed from Zenker in 1954 and MacKenzie in 1958, respectively.3-5
Until the dawn of the endovascular era, the accepted method of AEF treatment was solely open repair.1 However, endovascular repair is currently considered a promising method as a bridging therapy before open repair in high-risk patients. According to some authors, the endovascular approach can be used as a definitive therapy as well.2
The aim of this literature review is to assess whether endovascular AEF repair (eAEFr) is a safe definitive treatment for patients and examine which group of patients are most likely to benefit from this procedure.
Material and Methods
An extensive search in the PubMed indexing system (National Institutes of Health, Maryland, United States) was conducted. The key words for the search were “aortoenteric fistula,” “fistula,” “endovascular,” “open,” “AAA,” and “abdominal aortic aneurysm,” used along with the Boolean operators AND and OR. The literature search was limited by time period (July 1, 2000 to July 1, 2019) and by English language.
Our search yielded 72 manuscripts. Eleven additional manuscripts were found within the references of the 72 manuscripts. Of the 83 total manuscripts, 16 were excluded because the full text could not be retrieved and the abstracts did not provide enough data. Thirty-seven additional manuscripts were excluded because they were irrelevant to the review. Eleven manuscripts were on inflammatory and mycotic aneurysms, 9 did not mention any treatment of AEF, 6 referred to thoracic aneurysms and aortoesophageal fistulae, 3 referred to venointestinal fistulae, and 10 referred to complications of AAA.
Our search identified 30 studies reporting on 105 patients with AEF. The majority of the patients were male (n=87, 82.9%). The patients were between 35 and 91 years of age, with a median age of 73 years (Table 1).
The GI segment most affected by an AEF was the duodenum (n=17, 16.2%). Other segments of the GI tract were also affected, but less frequently than the duodenum. AEF were either primary (n=26, 24.8%) or secondary (n=60, 57.1%).
Both upper and lower GI bleedings were categorized as GI bleeding for the purpose of this study. The most common presenting symptoms were GI hemorrhage (n=94, 89.5%), abdominal pain (n=29, 27.6%), and fever (n=26, 24.8%). Some patients presented with more than one symptom, such as combined fever and GI hemorrhage (n=11, 10.5%). Approximately one-third of the patients (n=38, 36.2%) presented in shock. The less frequent symptoms are described in Table 2.
eAEFr was employed in 65 cases, but in 15 cases, this method was used only as a bridging therapy before open repair. Therefore, eAEFr was the definitive treatment in 50 patients (47.6%). Of these patients, 2 underwent additional femoro-femoral bypass, and 2 underwent more laparotomy for gut restoration. In 2 cases, (1.9%), the chimney technique was used to preserve blood flow to the renal arteries. Forty patients (38.1%) underwent an open repair, aortic reconstruction, axillofemoral bypass, or other procedures. For the purpose of this study, bridging endovascular procedures were grouped with the open repair cases, as the definitive therapy for the bridging endovascular procedures was open repair.
The follow-up period varied between 2 weeks and 4 years (median, 14.1 months). Complications included recurrent AEF (n=10), GI hemorrhage (n=7), multiple organ dysfunction syndrome (n=5), lower extremity ischemia (n=10), and graft infection (n=3). Less than half the patients received antibiotic treatment (n=48, 45.7%).
Due to the above complications, reintervention was necessary in 18 cases (17.1%) (Table 3). Reintervention was significantly more frequent in the eAEFr group (n=13, 12.4%) compared to the open repair group (n=5, 4.8%).
Fifty patients (47.6%) died from either procedure-related (n=15, 14.3%) or procedure-unrelated causes (n=35, 33.3%). There was no significant difference in the overall mortality in the open and the eAEFr groups (P>0.05) (Table 4).
The causes of primary AEF include a plethora of conditions. Both primary and secondary AEF are rather rare occurrences, although the incidence of each has changed over the course of time. A few decades ago, primary AEF was more common, but with more patients undergoing aortic repair, the number of secondary AEF cases has risen. Our results showed that every 2 out of 3 AEF cases involves a secondary AEF. Secondary AEF are usually the result of open abdominal repair of aneurysm or aorto-iliac occlusive disease. Secondary AER occur when the proximal suture line comes into contact with the GI tract, and in particular, with the duodenum.30 The overall incidence of both types of AEF has remained stable without a clear trend for the foreseeable future.
The demographics of the patients included in this study follow the already published data. AEF involves mainly males, probably due to the number of secondary AEF after aortic repair of an aneurysm, which occurs more frequently in males. The median age of patients was 73 years, also not a surprising finding.
eAEFr has already been suggested as a good bridging therapy that protects the patient from fatal bleeding and allows time to combat sepsis, improve the overall status of the patient, and stabilize the patient before a more permanent solution with an open repair.34 Other publications report that eAEFr is unsafe as a definitive solution to AEF, at least in the long run.30
eAEFr is linked to low morbidity, mortality, and length of hospital stay, as it is less invasive than open repair, especially in the short term.5,30 There is a valid skepticism regarding eAEFr, because a prosthetic material is placed in an already infected location, and 11 out of 50 deaths in our study were attributed to recurrent sepsis and sepsis-related multiorgan failure. In cases in which infection is isolated and there is no sepsis, eAEFr could be a good alternative to open repair.5,35 On the other hand, open AEF repair is demanding for the patient and frail patients might not be eligible for this high-risk solution.30 Therefore, eAEFr could be a good solution for this group of patients.
The most common presenting symptoms (GI bleeding, abdominal pain, and fever) described in our study are the ones mentioned in existing literature. A number of patients presented with sepsis, multiorgan failure, or shock due to sepsis. Sepsis is reported to be linked with worse outcomes after eAEFr.5,19
In our study, the complication rates of open repair and eAEFr were similar, and the incidence of each complication did not differ between the two groups. The reintervention rate was significantly higher for the eAEFr group; these patients were more prone to undergo an aortic reconstruction and axillo-femoral bypass than the open group patients. The necessity of abscess drainage and performing a femoro-femoral bypass was similar between the two groups.
Despite the fact that open repair is considered a permanent solution to AEF, aortic stump blowout syndrome and septic complications are not rare. 5 In our study, we found no aortic stump blowout cases, but sepsis and septic shock were similarly present in both the eAEFr and open repair groups. As mentioned earlier, sepsis and systemic infections are prognostic for worse patient outcomes. Both groups of our study showed the same incidence of sepsis and sepsis-related complications, as well as the same mortality for patients with sepsis. Therefore, open repair and eAEFr did not seem to influence the outcome regarding sepsis. Fever, as a sign of systemic infection, was also connected to worse outcomes.
Mortality was also similar between the open repair and the eAEFr groups, and the causes of death for the majority of the cases were common for the two groups.
To answer the question of whether endovascular repair can be a definite therapy for AEF, we needed to include a number of individual case reports, a small number of case series, and a multicenter study. These studies are not randomized, and the majority of them include one or few patients. The nature of AEF, as well as the declining incidence of secondary post-EVAR AEF, have not permitted the development of a randomized study to date. As a result, the evidence level of our results, and the results of publications similar to ours, is low. Conclusions should be accepted with a certain degree of caution.
In summary, eAEFr and open AEF repair have similar complications and mortality rates, but eAEFr demonstrates higher reintervention rates. As a bridging method, eAEFr has already demonstrated its promising results, but as a definitive therapy for AEF should only be considered in cases where sepsis or systemic infection are not present. Patients undergoing eAEFr as their final therapy should remain under rigorous follow-up for infection or bleeding. Future studies should focus on the role of eAEFr in subgroups of patients and seek to identify which subgroup(s) would benefit from eAEFr as a definitive therapy.
Disclosure: The authors report no financial relationships or conflicts of interest regarding the content herein.
Manuscript submitted November 17, 2019; manuscript accepted December 1, 2019.
Address for correspondence: Nikolaos Patelis, MD, MSc, PhD; Kifisias 56 & Delfon St, 15125 Marousi, Athens, Greece. Email: firstname.lastname@example.org
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