Dual complications of type I endoleak and aorto-enteric fistula post-EVAR: A case report and review of literature

Abstract

Aortoenteric fistula (AEF) is a rare but life-threatening complication following endovascular aortic repair (EVAR). Although individual complications such as endoleak and graft infection are well described, the simultaneous occurrence of an endoleak and AEF is exceedingly uncommon and poses significant diagnostic and therapeutic challenges. Most reported cases of this dual complication involve type II endoleaks; to our knowledge, this represents the first reported case of a type I endoleak occurring in conjunction with an AEF, specifically an aortocolic fistula. We describe a 94-year-old woman who presented with abdominal pain and sepsis 1 year after undergoing EVAR for a ruptured infrarenal abdominal aortic aneurysm. Contrast-enhanced computed tomography (CT) demonstrated a type I endoleak with associated graft infection and imaging findings highly suggestive of an aortoenteric fistula. This case adds to the limited existing literature and underscores the importance of maintaining a high index of suspicion for this potentially fatal dual complication, while highlighting the critical role of cross-sectional imaging in timely diagnosis and in guiding appropriate clinical management.

Introduction

Endovascular aneurysm repair (EVAR) is widely employed in the management of abdominal aortic aneurysms due to its reduced perioperative morbidity and mortality compared with open surgical repair However, long-term surveillance is essential because clinically significant delayed complications—including endoleaks, sac enlargement, device migration, limb occlusion, and less commonly endograft infection—may occur months to years after implantation [[1], [2], [3], [4], [5], [6]]. Endoleaks are reported in up to 30% of EVAR cases, whereas secondary aorto-enteric fistulas remain rare (reported at <2%) but are associated with substantial morbidity and high mortality [2,4,5,7]. Post-EVAR aorto-enteric fistulas are most often described as a late, infection- and/or inflammation-related process that may follow occult endograft infection, perigraft inflammation, or mechanical erosion and typically involve the duodenum; presentation ranges from herald gastrointestinal bleeding to nonspecific systemic infectious symptoms with estimated mortality rate of 30%-70% [2,7,8]. Contemporary reviews emphasize that cross-sectional imaging (particularly multiphasic CT angiography) is central to diagnosis, while adjunctive modalities (eg, FDG PET-CT and labeled white blood cell scintigraphy) can improve diagnostic confidence in suspected graft/endograft infection when CT findings are indeterminate [3,[9], [10], [11]]. In the published literature, most post-EVAR case reports and small series describe either (1) isolated endoleak-driven sac pressurization/expansion without systemic infection, or (2) isolated endograft infection with secondary aorto-enteric fistulation, often in the absence of active high-flow endoleak at the time of presentation [2,6]. Importantly, systematic evidence synthesis on endograft infection after EVAR demonstrates that these infections can present in a markedly delayed fashion and are associated with high mortality, particularly when patients are managed conservatively due to prohibitive operative risk [6].

In the existing literature, reported cases of post-EVAR AEF with concurrent endoleak overwhelmingly involve Type II endoleaks and predominantly aortoduodenal fistulas, with only isolated reports of nonduodenal enteric involvement. To our knowledge, no prior case has described a distal Type I (Type Ib) endoleak occurring in conjunction with an aortocolic fistula. The present case therefore represents a unique and clinically important contribution, highlighting both an unusual anatomic site of fistulization and a high-risk hemodynamic endoleak subtype. This report underscores the importance of maintaining a high index of suspicion and performing meticulous multiphasic CT evaluation when post-EVAR patients present with sepsis or nonspecific abdominal symptoms.

Case presentation

This case report follows a 94-year-old female patient with a past medical history of hypertension, hyperlipidemia, coronary artery disease status postpercutaneous coronary intervention, and ruptured infrarenal abdominal aortic aneurysm treated withEVARone year earlier presented to emergency carewith lower abdominal pain and fever. Laboratory results revealedleukocytosis and elevated serum lactate, consistent withsepsis (Table 1). Contrast enhanced CT of the abdomen and pelvis (AP) was performed at the portalvenous phase (GE scanner, 3mm slice thickness). Imaging demonstaratedan endovascular stent graft extending from the infrarenal aorta into bilateral common iliac arteries. The excluded aneurysm sac measured 6.3 × 6.0 cm on prior imaging and, 8 months later at presentation, measured 6.8 × 6.3 cm, consistent with interval sac expansion. There was visible contrast extravasation within the excluded aneurysmal sac near the distal graft attachment site, compatible with Type 1 (Type Ib) endoleak (Fig. 1A–C). Additionally, perigraft gas withinthe aneurysm sac wall, periaortic fat stranding, and obliteration of normal fat plane between the aneurysm sac and adjacent sigmoid colon were observed, raising strong suspicion for graft infection with secondary aortoenteric fistula formation(Fig. 1C–D). No definite contrast extravasation is noted through the suspected fistulous tract.

Table 1.

Pertinent blood laboratory results.

Lab parameters	Results	Reference
White blood cells (×10 ×3/µl)	12.2	4.3–11
Granulocytes (%)	82.9
Band cells (×10 ×3/µl)	0.19	(0–0.06)
Lactate (mmol/l)	9.08	(0.5–2.2)
C-Reactive Protein (mg/dl)	9.8	(<0.8)
Erythrocyte Sedimentation Rate (mm/h)	105	2–30

µl, microliter; mg/dl, milligram per deciliter; mmol/l, millimole liter; mm/hr, millimeter per hour.

Fig. 1.

Contrast-enhanced CT of the abdomen and pelvis. (A) Axial arterial-phase image demonstrating contrast extravasation at the distal graft attachment site (arrow), consistent with a Type I endoleak. (B) Coronal reformatted image confirming distal graft leak (arrow). (C) Sagittal image showing expanded aneurysmal sac with perigraft gas (upper arrow) and loss of the fat plane between the aneurysm sac and adjacent sigmoid colon (lower arrow) and (D) Axial image demonstrating intramural and perigraft gas with surrounding inflammatory fat stranding, suggestive of graft infection and aorto-enteric fistula.

Vascular surgery was urgently consulted and recommended definitive management with open surgical repair, including graft explantation and bowel resection. Given the patient’s advanced age, multiple comorbidities, and poor operative candidacy, the patient declined surgical intervention after extensive multidisciplinary discussion. Broad spectrum intravenous antibiotics were initiated and later escalated to intravenous piperacillin-tazobactam following blood cultures positive for Proteus mirabilis, a gram-negative rod. The patient developed septic shock 3 days after admission, necessitating vasopressor support and admission to the intensive care unit. After stabilization and a 10-day hospital stay, shewas discharged to hospice care on suppressive oral antibiotic therapy and analgesics.

Discussion

This case illustrates the exceptionally rare coexistence of 2 high-risk post-EVAR complications, a distal Type I endoleak and a secondary aortoenteric fistula, presenting with systemic infection rather than overt gastrointestinal hemorrhage. While both complications have been individually reported, their simultaneous occurrence remains exceedingly uncommon, and previously published cases have largely involved Type II endoleaks rather than high-pressure Type I endoleaks [2,4,5]. Previously reported individual cases describing the coexistence of endoleak and secondary aortoenteric fistula are summarized in Table 2, with emphasis on the radiologic features used to distinguish graft infection from fistulation.

Table 2.

Previously reported cases describing the coexistence of endoleak and secondary aortoenteric fistula.

Study	Repair type	Endoleak type	Enteric segment	Key radiological findings	Diagnostic emphasis	Management	Outcome
Antoniou et al. [15]	EVAR	Type II	Duodenum	Persistent sac opacification, perigraft gas, loss of aorto-duodenal fat plane	Infection with fistula	Surgical	Survived
Bas et al. [12]	EVAR	Type II	Duodenum	Perigraft gas, bowel wall thickening, inflammatory fat stranding	Infection predominance	Surgical	Variable
Lassandro et al. [11]	EVAR	Type II	Duodenum	Dynamic CTA showing aneurysm sac filling and bowel communication	Direct fistula confirmation	Endovascular	Survived
Mulita et al. [8] (case report)	Open repair	Not reported	Duodenum	Gas adjacent to graft, focal bowel erosion	Infection-driven fistula	Surgical	Poor
Present case	EVAR	Type I (Ib)	Sigmoid colon	Contrast extravasation within the distal graft sac, perigraft gas, loss of fat plane with colon	Endoleak + infection + fistula	Conservative	Hospice

Secondary AEFs following aortic repair most commonly involve the duodenum, accounting for the vast majority of reported cases, due to its fixed retroperitoneal position and close apposition to the infrarenal aorta [2,7,8]. In contrast, aortocolic fistulas are distinctly rare and have been described only sporadically in the literature, typically in the setting of advanced graft infection, extensive inflammatory change, or prior open surgical repair [7,8,12]. The present case is unusual not only because of the colonic involvement but also because it occurred in association with an active distal Type I endoleak, a combination that has not been previously reported to our knowledge. Multiphasic CT angiography remains the diagnostic cornerstone for evaluating suspected post-EVAR complications, as it allows simultaneous assessment of graft integrity, aneurysm sac dynamics, and surrounding soft tissues [11,13]. Type I endoleaks are optimally detected on arterial-phase imaging, where they appear as focal contrast extravasation at the proximal (Type Ia) or distal (Type Ib) graft attachment sites and are associated with persistent aneurysm sac pressurization and an increased risk of adverse outcomes [4,5,11]. Imaging findings suggestive of graft infection and secondary fistulization include perigraft gas, periaortic fat stranding, and loss of the normal fat plane between the aorta and adjacent bowel, with direct contrast communication to the gastrointestinal tract typically seen only in advanced cases [7,9,12,14]. Furthermore, PET-CT can serve as a useful adjunct in selected cases by identifying metabolically active infection when conventional CT findings are equivocal [9]. In our patient, portal venous-phase CT demonstrated perigraft gas and direct apposition of the graft to the sigmoid colon with loss of the intervening fat plane, findings that were highly suggestive of an aortocolic fistula despite the absence of direct contrast communication on the single-phase study.

Emerging artificial intelligence (AI)–based image analysis and clinical decision-support tools may further enhance detection of subtle post-EVAR complications. Machine learning algorithms have shown promise in automated endoleak detection and aneurysm sac volume quantification. Integration of AI-assisted analysis into radiology workflows may improve inter-reader consistency and reduce diagnostic delays, particularly in complex postoperative cases. Such tools may be especially valuable in elderly or high-risk patients where early recognition of overlapping complications is critical [16,17].The management of secondary AEF after EVAR typically involves urgent surgical intervention with graft explantation and bowel resection; however, outcomes remain poor, especially in elderly patients with significant comorbidities [[6], [7], [8]]. Conservative management is generally associated with high mortality but may be the only viable option in selected patients who decline or are not candidates for surgery, as in this case. This scenario provides valuable insight into the natural history and grave prognosis of untreated dual complications. This report is limited by the absence of surgical or autopsy confirmation and by restricted imaging follow-up due to palliative management. Nevertheless, the characteristic CT findings and clinical presentation provide strong diagnostic confidence.

Conclusions

The coexistence of a Type I endoleak and aorto-enteric fistula following EVAR is exceedingly rare and represents a diagnostic and therapeutic challenge with high mortality. This case underscores the essential role of meticulous cross-sectional imaging review in recognizing early radiologic signs of life-threatening post-EVAR complications. Prompt diagnosis can facilitate timely multidisciplinary decision-making and may prevent catastrophic outcomes.

Patient consent

A written informed consent was obtained from the patient for the publication of this case report.

Authorship

The authors declare that this is their original work, and they all approve the content of this manuscript. They confirm that this manuscript has not been published previously, in any language, in whole or in part, and is not currently under consideration elsewhere.

Ethical clearance

This project did not involve any research, and no ethical clearance was required.