What are aortoenteric and aortocaval fistulas, and how are they diagnosed?
Aortic aneurysms, usually when inflamed or infected, can erode into adjacent structures, such as bowel or the inferior vena cava, leading to connections between the aortic lumen and the lumina of these structures. The transverse portion of the duodenum and the inferior vena cava (IVC) are common locations for such fistulas as the expanding aneurysmal abdominal aorta exerts pressure on these adjacent structures. An aortoenteric fistula is suggested when there is a loss of fat plane between the enlarged aorta and the involved bowel loop, with inflammatory stranding in that region. Sometimes, air can be seen in the aortic lumen. If an aortoenteric or aortocaval fistula is suspected, imaging should first be performed without oral or intravenous contrast material, so that high attenuation in the affected bowel or IVC lumen on postcontrast scans can be correctly attributed to the fistula rather than from normal opacification by the administered contrast material