Aortoenteric fistula is an uncommon catastrophic cause of gastrointestinal haemorrhage. Aortic fistulas can be primary (associated with complicated abdominal aortic aneurysm) or secondary (associated with graft repair).
The annual incidence of primary aortoenteric fistulas is thought to be around 0.007 per million while that of secondary aortoenteric fistulas is about ~1% (range 0.6-2%) 1.
The incidence of secondary aortoenteric fistulas is found to be greater in patients following open aortic repair compared to patients with endovascular stent placement.
- initial presentation can be with a minor "herald" bleeding, which may be followed by a catastrophic, life-threatening gastrointestinal haemorrhage
- primary aortoenteric fistula: recurrent septicaemia with enteric pathogens
A primary aortoenteric fistula forms when a large abdominal aortic aneurysm closely abuts bowel loops, usually the 3rd or 4th parts of the duodenum. Due to long-standing pressure, the aneurysm slowly erodes into the bowel wall. These are most commonly due to infected mycotic aneurysms.
Secondary aortoenteric fistulas are seen as a complication of aortic reconstructive surgery with or without the placement of an aortic stent-graft. Secondary fistulas that result from perigraft infection may occur between 2 weeks and 10 years after surgery.
Primary aortoenteric fistula
Direct signs include:
- ectopic gas adjacent to or within the aorta
- the presence of vascular contrast within the gastrointestinal tract
Indirect signs include:
- bowel wall thickening overlying an aneurysm
- disruption of the aortic fat cover
- retroperitoneal haematoma or haematoma within the bowel wall or lumen
Secondary aortoenteric fistula
- increased perigraft soft tissue
- pseudoaneurysm formation
- disruption of aneurysmal wrap
- increased soft tissue between the graft and aneurysmal wrap
Treatment and prognosis
The only curative treatment is surgery. Without prompt surgical intervention, mortality approaches 100%. Operative mortality itself is as high as 50%.
On imaging consider
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- acute aortic syndrome
- thoracic aortic aneurysm
- abdominal aortic aneurysm
- endovascular aneurysm repair (EVAR)
- reporting tips for aortic aneurysms
- aortic coarctation
- aortic pseudocoarctation
- cervical aortic arch
- interrupted aortic arch
- transposition of the great arteries
- variant anatomy of the aortic arch
- traumatic aortic injury