Teaching Case

The patient was admitted due to massive gastrointestinal (GI) bleeding. He had previously undergone abdominal aortic aneurism repair with graft insertion. Upon hospitalisation esophagoduodenogastroscopy (EGD) and colonoscopy were performed. EGD did not identify any bleeding. Colonoscopy found massive blood in the colon. However, the source of bleeding could not be identified.

Contrast-enhanced CT of the of the abdomen and pelvis (Fig 1-3) was performed after the endoscopic procedures. Substantial extravasation of contrast from the aorta to the proximal jejunum was observed. Furthermore small amounts of ectopic gas were present within the aorta, as well as peri-aortic soft tissue infiltration. The fat plane between aorta and proximal jejunum was obliterated. The described findings were present near the proximal end of the aortic graft in keeping with secondary aorto-jejunal fistula.
Following CT, the patient underwent emergency surgery with closure of the fistula and partial excision of the infected graft. The patient was treated in the ICU for 2 weeks after the surgery, but was severely weakened by the massive haemorrhage. He had several instances of cardiac arrest, before he passed away.

Aorto-enteric fistulas are classified based on aetiology. The primary form is caused by atherosclerotic aortic aneurisms. The secondary form is far more common and occurs after aortic aneurysm surgery with or without graft insertion. Chronic low grade infection of the aortic graft and the aortic pulsations lead to formation of the fistula [1]. The 3rd and 4th part of the duodenum is involved in 80% of cases but any part of the GI tract from the oesophagus to the sigmoid colon may be involved [2]. Fistulation to the jejunum is uncommon, but possible as shown in the present case.
The patients usually present with one or more of the following symptoms and findings: GI bleeding, sepsis, abdominal pain, back pain, groin mass and abdominal pulsatile mass [3]. Catastrophic GI bleeding is usually preceded by short, self-limiting, bleeding - hours to days before (herald bleed).
The diagnosis is usually made with either endoscopy or contrast-enhanced CT. EGD can usually identify fistulas in the oesophagus or duodenum. Contract-enhanced CT is more often used in an emergency setting due to availability. CT signs of aorto-enteric fistulas are perigraft ectopic air, soft-tissue attenuation and loss of fat plane between aorta and the involved GI-tract. Furthermore, contrast extravasation is uncommon but may be present if there is active bleeding [4]. All the mentioned signs were observed in the present case.
The condition is life threatening and requires prompt surgical treatment. Several surgical procedures are available, such as graft excision and extra-anatomic bypass, in situ graft replacement, and simple graft excision [5]. If untreated, mortality is approaching 100%. Thus promo diagnosis of this condition is crucial.
In conclusion, the present case illustrates typical imaging findings of an aorto-eneteric fistula with an uncommon location.