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Case 96

Aortoduodenal fistula

Unusual cause of gastrointestinal bleeding

Erica Buurman, Richard Edwards

A 54 year old man was admitted with a 1-day history of significant melaena associated with mild epigastric pain. His past history included ischaemic heart disease, chronic renal failure (treated by peritoneal dialysis) and aortic aneurysm repair 3 years previously. His haemoglobin on admission was 8.8 g/dl with a white cell count of 12.8. Upper gastro-intestinal (GI) endoscopy to the second part of the duodenum showed no source of bleeding. He was referred for visceral arteriography because of continued melaena. During the procedure his systolic blood pressure remained below 90 mmHg.

There is diffuse spasm in the branches of the coeliac and superior mesenteric arteries due to hypotension. There is reversed flow in the gastroduodenal artery. An AP flush aortogram was also performed (not shown) but no extravasation was demonstrated.

The patient's condition remained unstable requiring further blood replacement. Contrast enhanced CT was performed.

There is a defect in the anterior wall of the (repaired) aortic aneurysm contiguous with the third part of the duodenum. Increased attenuation material is present in the third part of the duodenum (the patient was not given oral contrast). Small bubbles of gas in the aneurysm sac and periaortic inflammatory tissue are also present. Note also the presence of peritoneal dialysis fluid.

Diagnosis

Aortoduodenal fistula

Discussion

Aortoenteric fistula (AEF) is a rare but potentially fatal complication of aortic aneurysm surgery with a reported incidence of 0.4 to 2.4%. This may occur as a primary complication of aneurysm repair or may present several years after surgery. AEFs most commonly involve the third or fourth parts of the duodenum but may involve the small bowel or colon in up to 20% of cases. Several mechanisms may be involved in their formation including failure to separate bowel from the graft. Adhesion between these two structures can lead to pressure necrosis particularly at the suture line due to repetitive trauma caused by the pulsating graft. Contamination of the graft with gut organisms is common. Approximately 50% of the patients with an AEF present with haematemesis or melaena but massive GI haemorrhage is rare. Other features may include abdominal pain and a pulsatile mass. Diagnosis is difficult and a high index of suspicion should be maintained in patients with unexplained GI bleeding and a previous history of aortic aneurysm repair. Endoscopy is the initial investigation of choice to exclude other more common causes of GI haemorrhage, although rarely the point of graft erosion may be identified. Barium studies are usually not helpful and dense contrast may interfere with CT or MR imaging. Laparotomy may be necessary in some cases, if imaging studies are negative. Surgical treatment usually involves extra-anatomic vascular bypass, removal of the infected graft, closure of the aortic stump and repair of the bowel defect. Unfortunately conventional surgical treatment is associated with a perioperative mortality of 25 to 90%.

References

Busuttil SJ, Goldstone J. Diagnosis and management of aortoenteric fistulas. Semin Vasc Surg 2001;14:302-311

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