Aorticenteric Fistula (AEF):
There are two different types of AEF:
Primary: Occurs when a chronic, untreated aortic aneurysm damages or destroys the aortic and bowel tissue.
Secondary: Occurs due to inflammation of previous aortic graft surgery that is near a section of bowel. This type is much more common than primary AEF.
AEF must be considered in any patient with GI bleeding and history of abdominal aortic surgery. Although AEF is not the most common cause of GI bleeding in these patients, it is life threatening.
The most common location is along the third or fourth portion of the duodenum. A large abdominal aortic aneurysm can erode primarily into the duodenum at these locations, resulting in fistula formation.
Fun fact: Postoperative AEF is most often associated with a graft infection.
Aortoenteric fistula can present with a sentinel or herald bleed that is minor, or with a sudden catastrophic bleed with hematemesis, melena, or hematochezia (so don’t rely on just upper or lower GI bleed).
If the patient is hemodynamically unstable, emergent laparotomy and blood transfusion are needed. If the patient’s condition is stable, upper GI endoscopy or CT angio of abdomen/pelvis (but you may just want to get the whole aorta). This is a good example of why it’s good to have both surgery and GI consults for your GI bleeds.
In a patient I had with this diagnosis, they had severe AKI he and we attempted to get a CTA but MRA was recommended/insisted by the radiologist (the patient was very stable). The radiologists were refusing to take this patient to CT due to the Cr. In the end, we learned that in order to get an accurate MRA, the patient needs to stay extremely still and pretty much not breath (…not practical). So after all the effort to get this patient to MRI, they ended up getting the CTA anyway, just hours later. Luckily this patient still did well but it was stressful sending them so far away to MRI land. Learn from my mistakes.
In the image below, this classic triad (GI bleed, abdominal pain and palpable mass) occurs in 6-12% of AEFs. Good for MCQs, bad for real life.
Sources:
Text: peer review, https://www.uptodate.com/contents/aortoenteric-fistula-recognition-and-management
Photo: Rosh review
