Teaching Case

A 56-year-old male patient presented to the ER in haemorrhagic shock with upper and lower GI bleeding. 5 years previously he had an aorto-bi-femoral graft for an aortic aneurysm. An aorto-duodenal fistula was found on CT, which the surgeons managed to suture, but due to ischaemic complications the patient eventually expired.

An Upper GI endoscopy was performed and revealed a massive quantity of fresh blood in the stomach and duodenum, with no identifiable cause for this, so a CT was requested.
In the unenhanced abdominal CT, a distended stomach filled with fresh blood and blood clots were visible (Fig. 1). An aorto-bi-femoral synthetic stent is faintly seen on the unenhanced CT, with no fat plane separating the aorta and the 3rd part of the duodenum (Fig. 2). In the arterial phase of the contrast enhanced abdominal CT, an aorto-duodenal fistula is clearly visible. Blood is seen going from the aorta into the 3rd portion of the duodenum (Fig. 3 and 4). In the portal phase a more extensive collection of blood is seen in the duodenum and jejunum (Fig. 5).

Aortoenteric fistula (AEF) is a communication between the aorta and the gastrointestinal (GI) tract. It is a rare but life threatening condition [1]. AEF is classified into two categories: primary and secondary [1-6]. A primary AEF results from diseases such as abdominal aortic aneurysm, infectious aortitis, penetrating peptic ulcer and tumour invasion. A secondary AEF is a much more common entity and is a complication of aortic prosthetic grafting – like in our case. It occurs in 0.3% to 2% of patients [1, 3, 5]. There are 2 types of secondary AEF. Type-1, the more common one, develops between the proximal aortic suture line and the bowel and is associated with massive upper GI haemorrhage. Type-2 accounts for 15-20% of secondary AEF. There is no communication between the bowel and the graft [3]. Sepsis (75%) is more likely to occur with this type of fistula than GI bleeding (30%) [4].
Aortoduodenal fistula (ADF) is the most frequent of the aortoenteric fistulae (73%). The third part of duodenum is most commonly involved [1, 2, 4].
Risk factors for developing a secondary AEF are associated with the aortic stenting procedure. This procedure may be complicated by perigraft haematoma due to perioperative thrombolysis, infection due to prolonged intragraft cannulation and stent-related aortic injury, especially if an endarterectomy has been performed. Endarterectomy creates a weakened aortic wall which is more prone to develop lesions, such as aortic perforation or pseudoaneurysm [7].
Due to its availability, short acquisition time, and high resolution, computed tomography (CT) is the initial diagnostic test of choice [1, 6]. Perigraft soft-tissue oedema, fluid and ectopic gas are normal CT findings immediately after surgery. After 3–4 weeks however, any ectopic gas should be considered a sign of perigraft infection and possible fistulisation to bowel. Other CT findings that are suggestive of both perigraft infection and aortoenteric fistula include pseudo-aneurysm, loss of the normal fat plane between the aorta and the adjacent bowel and disruption of the aortic wall [1, 6].
Management of aortoenteric fistulas consists of extra-anatomic bypass combined with aortic ligation or in situ aortic reconstruction. If the surgical intervention is not prompt, the mortality rate is near 100% [1, 3, 5]. In patients who survive there is a 10-40% prevalence of limb loss [2].