Aortoenteric Fistula

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 22/04/2025

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(Left) Graphic shows a fistula image between the transverse duodenum and aorta at the site of the graft-aortic suture line image.

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(Right) Axial CECT in a 70-year-old man presenting with fever and hematemesis months after abdominal aortic aneurysm (AAA) repair shows the native, calcified aortic wall image wrapped around a synthetic graft. A gas collection is noted between the graft and aortic wall image, indicating infection or fistula. Note the soft tissue density surrounding the aorta and 3rd portion of duodenum image.
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(Left) This elderly woman had pain and fever years after AAA repair. Axial CECT shows a calcified aortic wall wrapped around synthetic graft material image. At the level of the 3rd portion of the duodenum, the duodenal wall image appears to be adherent to the aorta. Note an enhanced focus image that may represent active bleeding or inflammation.

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(Right) Axial CECT in the same patient reveals several bubbles of extraluminal gas image; aortoenteric fistula with underlying infection was surgically confirmed.

TERMINOLOGY

Definitions

• Abnormal communication between aorta and gastrointestinal (GI) tract

IMAGING

General Features

• Best diagnostic clue

image Inflammatory stranding and gas between abdominal aorta and 3rd part of duodenum following aneurysm repair
• Location

image Duodenum (80%); jejunum and ileum (10-15%); stomach and colon (5%)

CT Findings

• Microbubbles adjacent to aortic graft
• Focal bowel wall thickening &/or perigraft soft tissue thickening > 5 mm
• Pseudoaneurysm, disruption of aneurysmal wrap
• Contrast in pseudoaneurysm on arterial phase
• Arterial phase: ↑ attenuation of intestinal lumen contents 

image Attenuation of intestinal contents may decrease on delayed phase through same region
image Volume of intestinal blood may increase on delayed phase
• CT-guided needle aspiration: May confirm perigraft infection

Nuclear Medicine Findings

• PET/CT

image Site of infection/fistula is usually FDG-avid on PET
• Tagged RBC study 

image Radiolabelled RBC accumulate within bowel at site of fistula
• Tagged WBC scan can confirm infection

Imaging Recommendations

• Best imaging tool

image CT: 94% sensitive; 85% specific
image PET/CT may be even better

– CT portion of exam should be of diagnostic quality with IV contrast administration

DIFFERENTIAL DIAGNOSIS

Periaortitis

• Inflammatory perianeurysmal fibrosis
• Soft tissue attenuation encases aorta, IVC

Retroperitoneal Fibrosis

• Mantle of soft tissue enveloping aorta, IVC, ureters

Postoperative Changes

• Perigraft fluid may persist for up to 3 months

Postendovascular Stent

• Endoleak: Blood flow outside stent but within aneurysm sac or adjacent vascular segment
• Gas bubbles between stent-graft and aortic wall

PATHOLOGY

General Features

• Etiology

image Primary: Abdominal aortic aneurysms, infectious aortitis, penetrating peptic ulcer, tumor invasion, radiation therapy
image Secondary: Most common type, usually following aortic reconstructive surgery 

– Can occur after “open”/endovascular aneurysm repair
image Pathogenesis

– 3rd portion of duodenum fixed and apposed to anterior wall of aortic aneurysm → pressure necrosis
– Surgery → blood supply compromised
– Pseudoaneurysm formation with erosion
– Graft and suture line infection → anastomotic breakdown
– Aortocolonic fistula may follow aortoiliac graft

image Sigmoid diverticulitis near graft site may lead to fistula from colon to iliac artery/graft
• Associated abnormalities

image Aortic aneurysm or atherosclerosis; perigraft infection

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image “Herald” GI bleeding, followed hours, days, or weeks later by catastrophic hemorrhage
image Abdominal/back pain, palpable and pulsatile mass
image Intermittent rectal bleeding and recurrent anemia
image Low-grade fever, fatigue, weight loss, leukocytosis

Demographics

• Age

image 55 and older
• Gender

image M:F = 4-5:1
• Epidemiology

image Incidence: 0.6-1.5% after aortic surgery
image Onset after surgery: 21 days to 14 years

Natural History & Prognosis

• Very poor prognosis, up to 85% mortality

Treatment

• Percutaneous drainage of infected perigraft fluid may be initial treatment, followed by surgery
• Emergent reconstructive surgery may be required; removal of infected graft is usually required

DIAGNOSTIC CHECKLIST

Image Interpretation Pearls

• Perigraft infection evidenced by ectopic gas or perigraft soft tissue raises suspicion of fistula
image
Axial CECT shows an aorto-enteric fistula. Note the ectopic gas image and abnormal perigraft soft tissue indicating infection image. (Courtesy F. Hughes, MD.)

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Axial CECT shows a primary aorto-enteric fistula. Note the large abdominal aortic aneurysm (AAA) leaking into the peri-aortic hematoma image. The transverse duodenum image is draped over the hematoma.
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Axial NECT shows a large AAA. Note the crescent sign image of higher density between the aortic intimal calcification and patent lumen.
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Axial CECT in the same patient shows gas image within the thrombus, suggesting infection &/or communication to the bowel lumen. The 3rd portion of the duodenum stretches over and appears to adhere to the AAA image.
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Axial CECT shows fluid and a gas bubble between the graft lumen and aortic wall, which is wrapped around the graft. At surgery the graft was infected and a fistula was found between the graft and the duodenum image.
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Barium enema shows an extravasation of contrast which outlines a left common iliac artery graft image.
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Fatal aorto-duodenal fistula and hemorrhage. Axial NECT shows a mantle of soft tissue and gas surrounding the abdominal aorta and graft.

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