Anna Maria Rüütmann,Jaak Kals
Primary and secondary aortoenteric fistulas in a patient with abdominal aortic aneurysm
Vascular surgery,Cardiovascular disorders,Aortic repair,Abdominal aortic aneurysm,Aortoenteric fistula
Introduction Aortoenteric fistulas (AEF) are infrequent malignant complications of abdominal aortic aneurysms (AAA). We present a unique case of a patient with recurring AAA fistulisations. Presentation of case During oncologic treatment, a 63-year-old male was incidentally diagnosed with infrarenal AAA and assigned follow-up but was hospitalised with anaemia and elevated inflammation markers 14 months later. A CT-angiography scan detected an AAA enlargement, but no extravasation (negative FOBT). Another CTA-scan displayed a pseudoaneurysm and ruptured AAA 10 days later. During a total laparotomy, an enlarged pulsating inflammatory conglomerate without active leakage was detected, with a 2 cm duodenal defect (PAEF). The AAA was resected and replaced by a linear silver-coated Dacron graft. 3,5 years after PAEF, the patient was hospitalised with abdominal pain and haematemesis. He underwent gastroscopies, coloscopies, CT- and CTA-scans – all without significant findings. Only after the capsule-endoscopy detected a jejunal ulcer, the PET-scan visualized active regions in the jejunum and the aortic graft. A total laparotomy was performed; previous stapler-lined jejuno-jejunal anastomosis had adhered to the silver-coated Dacron graft (SAEF). The Dacron graft was removed and replaced with a linear xenograft from bovine pericardium. Discussion No evidence-based recommendations prefer endovascular aneurysm repair (EVAR) over open repair, leaving the strategy dependent on local preferences. Whether EVAR or initial xenograft usage would have shown surpassing results, is speculative, as no graft material/type has proved long-term pre-eminence. Conclusions This case displays AEF's complex treatment and challenging diagnosis. Multimodal diagnostic and strategic approaches should be considered for best patient outcome.
Primary and secondary aortoenteric fistulas in a patient with abdominal aortic aneurysm

Aortoenteric fistulas (AEF) are infrequent malignant complications of abdominal aortic aneurysms (AAA). We present a unique case of a patient with recurring AAA fistulisations.

During oncologic treatment, a 63-year-old male was incidentally diagnosed with infrarenal AAA and assigned follow-up but was hospitalised with anaemia and elevated inflammation markers 14 months later. A CT-angiography scan detected an AAA enlargement, but no extravasation (negative FOBT). Another CTA-scan displayed a pseudoaneurysm and ruptured AAA 10 days later. During a total laparotomy, an enlarged pulsating inflammatory conglomerate without active leakage was detected, with a 2 cm duodenal defect (PAEF). The AAA was resected and replaced by a linear silver-coated Dacron graft. 3,5 years after PAEF, the patient was hospitalised with abdominal pain and haematemesis. He underwent gastroscopies, coloscopies, CT- and CTA-scans – all without significant findings. Only after the capsule-endoscopy detected a jejunal ulcer, the PET-scan visualized active regions in the jejunum and the aortic graft. A total laparotomy was performed; previous stapler-lined jejuno-jejunal anastomosis had adhered to the silver-coated Dacron graft (SAEF). The Dacron graft was removed and replaced with a linear xenograft from bovine pericardium.

No evidence-based recommendations prefer endovascular aneurysm repair (EVAR) over open repair, leaving the strategy dependent on local preferences. Whether EVAR or initial xenograft usage would have shown surpassing results, is speculative, as no graft material/type has proved long-term pre-eminence.

This case displays AEF's complex treatment and challenging diagnosis. Multimodal diagnostic and strategic approaches should be considered for best patient outcome.

Aortoenteric fistulas (AEFs) are infrequent malignant complications of abdominal aortic aneurysm (AAA). AEF is defined as an anomalous connection between the aorta and the gastrointestinal (GI) tract. Primary AEFs (PAEFs) predominantly derive de novo from the compression of an AAA, and secondary AEFs (SAEFs), from the compression of an aortic prosthetic graft, against neighbouring GI structures. The annual occurrence of PAEF is documented to be <1 % (underdiagnosed), while the incidence of SAEF is 0.36..0.1.6 % [1,2,3]. Over 75 % of PAEFs involve the duodenum (i.e., aortoduodenal fistula). The pathological fistulisation in SAEFs most frequently involves a surgically replaced aortic graft and the duodenum [[4], [5], [6]]. We report a unique case of a patient with recurring AAA fistulisations, appearing as a PAEF and a SAEF, and present a review of the literature. The aim of this report is to accentuate the deceptive clinical manifestations of AEF and the challenges of a timely diagnosis.

A 63-year-old male patient was initially diagnosed with signet ring cell carcinoma (SRCC) in the gastric corpus. Neoadjuvant chemotherapy was administered, followed by gastrectomy with a Roux-en-Y reconstruction. The postoperative period proceeded with full recovery and during the treatment an infrarenal AAA with a diameter of 4.1 cm was diagnosed, the patient was assigned follow-up. Fourteen months after the incidental AAA diagnosis, the patient was admitted to the hospital due to urosepsis, pyelonephritis and anaemia (Hb 85 g/L). Despite previous antibiotic therapy, the inflammation markers remained high (WBC 33.3 × 109/L; CRP 87 mg/L; PCT 3.3 ng/mL). A computerized tomography angiography (CTA) scan detected AAA enlargement from 41 mm to 54 mm within 12 months and a thrombosed intramural haematoma (9 mm) in the right aortic wall (Fig. 1A). No extravasation was yet perceivable, the patient was assigned possibly fatal rupture risk monitoring. After 10 days of hospitalisation with nonspecific symptoms (subfebrile fever, constipation), the patient's condition worsened, presenting severe fatigue and anaemia (Hb 78 g/L, Hct 23 %, CRP 123 g/L, PCT 6.5 ng/mL). A negative faecal occult blood test (FOBT) and absent GI tract bleeding symptoms contributed to diagnostic delay. The second CTA scan detected a ruptured AAA (rAAA) in the previously thrombosed intramural haematoma region (Fig. 1B), with a new anteriorly located pseudoaneurysm (44x43mm). The patient was immediately admitted for urgent operation. During the total laparotomy, an enlarged pulsating inflammatory conglomerate without active blood leakage was detected. A 2 cm defect (i.e., PAEF) was found in the duodenum, resulting in duodenal compression and inadequate perfusion: the entire pars ascendens appeared necrotic (the previous surgical manipulations of oncologic surgery had remained completely intact). The brittle and inflamed infrarenal AAA was resected (infrarenal cross-clamping technique) and replaced by a 16 mm linear silver-coated Dacron graft. A complete resection of pars horizontalis and pars ascendens was carried out without any severe postoperative complications. In 40 months, the patient was readmitted to the hospital after recurrent fainting episodes, pain in the abdomen, haematemesis (Hb 98 g/L), and severe idiopathic hypoglycaemia (1.7 mmol/L). He received several red blood cell (RBC) transfusions and underwent CT and CTA scans, gastroscopies and coloscopies – all without any clinically significant findings. Only after the capsule-endoscopy detected a jejunal ulcer, the positron emission tomography (PET) scan visualized metabolically active regions in the distal jejunum and the aortic graft. However, the finding was not sufficient for making a definite diagnosis (Fig. 2). Preoperatively, two main diagnostic hypotheses were suggested: a tumour or a SAEF. A total laparotomy was performed: the previously formed stapler-lined jejuno-jejunal anastomosis had adhered to the silver-coated Dacron graft, and the diagnosis of SAEF (between the distal anastomosis of the Dacron prosthesis and the jejunum) was confirmed (Fig. 3). After infrarenal aortic cross-clamping, the Dacron graft was fully removed and sent for microbiological analysis (reporting no malignancy or infection) and replaced with a new linear xenograft. Intravenous antibiotic therapy was continued for 4 weeks postoperatively and per os acetylsalicylic acid was initiated. Thirty months after the surgical treatment of SAEF the patient had no specific symptoms of aortic or intestinal pathology; a follow-up CTA confirmed the aortic graft to be intact, without any signs of inflammation or fistulisation (Fig. 4).

PAEF is an extremely uncommon (0.04…0.07 %) and potentially fatal complication of AAA. Effective management requires timely diagnosis and combined treatment modalities. The classic diagnostic triad of abdominal pain, pulsating abdominal mass and upper GI tract bleeding, occurs in only 25 % of the patients. Signs of systemic infection are rarely present, making the diagnostic process even more difficult [7,8]. It remains unclear why symptoms of GI tract bleeding may be absent in AEF patients. Previous cases have presented an initial self-limiting haemorrhage (sentinel haemorrhage), leading to a massive haemorrhage usually within 6 h, while the interval between bleedings can be several months [7]. Herald bleeding is time limited, resulting from the spontaneous obstruction of the fistula by a temporary thrombus and the spasm/contraction of the intestine around the bleeding site [8,9]. No melena was detected and FOBT was negative, but FOBT is not always accurate. Compared with upper or lower GI tract endoscopy, FOBT was 58 % sensitive and 84 % specific for diagnosing any GI abnormality in patients with anaemia [10]. Possibly, the bleeding was subtle and occurred over a longer period, causing a continuous drop in haemoglobin. Therefore, herald bleeding is an early subclinical sign of AEF and a key finding for timely diagnosis. To the best of our knowledge, no previously published case has presented a consecutively occurring PAEF and SAEF in the same patient. After the successful treatment of PAEF, our patient developed a SAEF 40 months later. SAEF is generally a complication of the chronic infection of an aortic synthetic graft or stent graft, occurring usually 36…60 months postoperatively [11,12]. However, in the present case the microbiological analysis of the blood, the aortic tissue and the removed aortic graft revealed no signs of infection. As aortic graft infections (without AEF) mimic radiological signs of AEF, they are difficult to distinguish and detect [12]. Absence of exact findings of diagnostic imaging is often characteristic of SAEFs. Only a capsule endoscopy detected a bleeding site in the jejunum in our case, and the PET-scan showed metabolically active regions in the grafted aortic wall, but this was not specific enough for the diagnosis. The majority of SAEF diagnoses are confirmed intraoperatively. Patients may present no active bleeding or leaking in esophagogastroduodenoscopy, total colonoscopy, and CTA scans, with some extreme asymptomatic cases displaying gas locules and surrounding inflammatory fat strandings in imaging as only diagnostic clues. However, despite the diagnostic challenges, CTA remains the preoperative diagnostic modality of choice with adequate sensitivity and specificity (94 % and 85 %, respectively) for the diagnosis of SAEF. CTA findings often show periaortic inflammatory changes such as fat stranding, perigraftic fluid, periaortic foci of gas – which were absent in our imaging, enhancing the complexity of the case. Another possible imaging technique would be the MRI, but it lacks reliability in depicting the occurrence of aortic extraluminal gas [11,13,14]. In the present case PET-scan had greater diagnostic value, yet they tend to yield a greater number of false positive results and the obtained data should be considered with other clinical parameters [13]. Yet, Krupnick et al. showed that PET imaging with 18-fluorodeoxyglucose (FDG) can rapidly detect areas of inflammation with increased glucose metabolism, potentially leading to earlier surgical intervention. As there is no single diagnostic investigation with very high specificity and sensitivity, it is common for the final diagnosis of SAEF to be confirmed during surgical exploration [15]. AEF treatment is multimodal, consisting of surgery, intensive care, and antimicrobial therapy with appropriate follow-up management. Due to the high morbidity associated with OSR, the usage of EVAR for treatment of AAA with AEF has recently grown in popularity [1] and may be used as a bridging procedure in terms of definitive fix by OSR [16]. There are no evidence-based recommendations about preferring EVAR over OSR in AEF treatment, leaving the suitable strategy to be determined by the local centres' experience [17,18]. If a primarily replaced aortic graft is removed during SAEF treatment, instant reconstruction is necessary. This increases the need for extra-anatomic bypasses [1] or using a custom-made xenograft – as in our case. We can only speculate whether an initial EVAR or using a xenograft instead of the silver-coated graft in PAEF treatment would have given more favourable results. According to the recent European Society of Vascular Surgery Guidelines, no graft material or type is superior to another in terms of long-term results [17]. Empiric antibiotic therapy has been suggested for AEF patients. According to the guidelines, the length of antimicrobial therapy is set on an individual basis, ranging from a few weeks to lifelong administration [17]. Our patient received intravenous Cefuroxime for 4 postoperative weeks and per os aspirin as continuous therapy. Using antiplatelet agents has been proved to reduce thrombus formation, stabilize aortic wall and decrease aortic wall inflammation [17,19].

This extremely rare case highlights the deceptive clinical manifestations and diagnostic difficulties of PAEF and SAEF. A multimodal approach, including adequate surgical expertise, intensive care, antibacterial therapy with long-term surveillance is necessary for favourable short- and long-term patient outcome.

AAAabdominal aortic aneurysmAEFaortoenteric fistulaCRPC-reactive proteinCTcomputerized tomographyCTAcomputerized tomography angiographyEVARendovascular aneurysm repairFDGfluorodeoxyglucoseFOBTfaecal occult blood testGIgastrointestinalMRImagnetic resonance imagingOSRopen surgical repairPAEFprimary aortoenteric fistulaPCTprocalcitoninPETpositron emission tomographyRBCred blood cellSAEFsecondary aortoenteric fistulaSRCCsignet ring cell carcinomaWBCwhite blood cell count

This case report was conducted in accordance with the Declaration of Helsinki. The collection and evaluation of patient health information was performed with written consent of the patient. Ethical approval for this case report (Ethical Committee N° 283/T-10) was provided by the Ethical Committee of University of Tartu, Tartu, Estonia on 18 June 2018.

This study was funded by personal research grant from the 10.13039/501100002301Estonian Research Council (PRG no. 1437).

Ms. Anna Maria Rüütmann; Prof. Jaak Kals, MD, PhD.

Written informed consent was obtained from the patient's guardian for publication of this case report and any accompanying images.

This case report is not under consideration for publication elsewhere, its publication is approved by all authors. If accepted, this case report will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder.

This case has been reported in line with the SCARE criteria [20].

Anna Maria Rüütmann: Data curation, Formal analysis, Writing – original draft. Jaak Kals: Conceptualization, Data curation, Supervision, Writing – review & editing.

None.