CASE 18526 Published on 16.04.2024

Aortoenteric fistula following Onyx embolisation of a type 2 endoleak


Interventional radiology

Case Type

Clinical Case


Yunus Hussain, Ali Zaman, Imran Syed, Noreen Rasheed, Rumman Ahmed

Basildon & Thurrock University Hospital, Mid and South Essex NHS Foundation Trust, Basildon, United Kingdom


81 years, male

Area of Interest Interventional vascular, Vascular ; Imaging Technique CT-Angiography
Clinical History

An 81-year-old male presented with abdominal pain, malaise, and weight loss one month after undergoing a transarterial embolisation of a type two endoleak (T2E) for an expanding abdominal aortic aneurysm sac post-endovascular aortic repair (EVAR). His blood infection markers were markedly raised, and his blood culture was Clostridium perfringens positive.

Imaging Findings

Computer Tomography (CT) imaging from two months earlier (Figures 1a, 1b and 1c) showed a persistent T2E from the lumbar L4 arteries with a rapid 2cm increase in aneurysm sac diameter over 3 months. Additionally, there was adjacent retroperitoneal fat stranding which was concerning for an unstable aortic sac.

After a multidisciplinary team discussion, a transarterial approach via the left iliolumbar artery was selected for T2E embolisation using Onyx in order to fill the nidus and ostia of contributing lumbar arteries (Figure 2). Whilst variations in techniques and agents exist [19], it was felt that Onyx alone would be sufficient and perhaps allow more comprehensive filling of any unidentified contributing arteries.

One month post-embolization, a CT-angiography (Figures 3a, 3b and 3c) showed ongoing T2E and extensive intra-aneurysmal gas, indicating potential gas gangrene. Although there was no contrast extravasation into the bowel, an adjacent distal ileal bowel wall appeared inflamed and adherent to the aneurysm sac; this was interpreted as an aortoenteric fistula (AEF). Blood cultures grew Clostridium perfringens, suggestive of aortic gas gangrene.


EVAR has become a mainstay in treating abdominal aortic aneurysm (AAA). Recognised complications include endoleaks and infection. T2Es are caused by retrograde blood flow into the aneurysm sac from arterial branches arising from the stented aortic segment, most commonly from the inferior mesenteric or lumbar arteries. T2Es occur in up to 20% of cases and can cause sac expansion and rupture. Treatment involves embolisation with coils, liquid embolics or a combination of the two [20]. Onyx, an ethylene vinyl alcohol copolymer, is one such liquid embolic with a reported 80% sac stabilisation rate. Approaches in accessing the nidus of T2Es include the transarterial, direct sac puncture and transcaval routes [1–3].

Endograft infections (EI) occur in <1% of cases and typically >2 years post-EVAR. They carry a mortality rate of up to 59% [4]. Patients may present with pain, fever, rigors, lethargy and gastrointestinal (GI) haemorrhage [5].

Secondary AEFs occur in 0.46% of cases and present similarly to EIs but with a greater predisposition for GI haemorrhage [6].

Rare cases of AEFs developing post-coil embolisation of endoleaks have been documented but none following Onyx embolisation [7,8].

CT-angiography is the chosen imaging modality for EIs and AEFs due to its high sensitivity. Oesophagogastroduodenoscopy, positron emission tomography-CT or magnetic resonance imaging may also be considered [6,9,10].

Despite the absence of contrast extravasation into the bowel in this case, other indirect AEF features were present, including peri-graft gas and effacement of the peri-aneurysmal soft tissue and adjacent apposing bowel wall [6,11].

AEF management includes graft explantation, extra-anatomical revascularisation, and fistula exclusion [5,10,12,13]. Although perioperative mortality is high, conservative management is associated with 100% mortality after 1 year [13,14].

Clostridium perfringens is an anaerobic gram-positive bacillus found in intestinal flora, soil, and raw meat. It is commonly associated with GI infections and can cause myonecrosis [15].

Rare cases of EIs with Clostridium perfringens have been documented occurring in the context of AEFs [16–18]. However, there are no documented cases of EIs with enteric organisms following transarterial T2E embolisation with Onyx.

We postulate that our patient developed sepsis following Clostridium perfringens translocation from the small bowel into the aortic aneurysm via an AEF, which developed spontaneously following T2E Onyx embolisation. Sadly, the patient died shortly after admission.

Teaching points

  • AEF is a rare but severe complication of EVAR.
  • Endoleak embolisation with Onyx could be associated with AEF development.
  • Optimal management for AEFs involves surgical intervention despite high perioperative mortality rates.
Differential Diagnosis List
Clostridium perfringens infection post-endoleak embolisation secondary to an aortoenteric fistula
Peri-graft infection without an aortoenteric fistula
Mycotic aortic aneurysm infection with another organism
Inflammatory aortitis
Final Diagnosis
Clostridium perfringens infection post-endoleak embolisation secondary to an aortoenteric fistula
Case information
DOI: 10.35100/eurorad/case.18526
ISSN: 1563-4086