The red connection: a review of aortic and arterial fistulae with an emphasis on CT findings.

Fistulae between the aorta and adjacent structures are a rare, emergent, and potentially life-threatening process. Most commonly, aortic fistulae arise secondarily as a complication of prior aortic surgery with fistulization to adjacent structures. Rarely, a primary fistula may arise from the aorta in the setting of a pre-existing aneurysm or from a mass, inflammation, or infection. Although the incidence of aortic fistulae remains low, the frequency continues to increase as aortic surgical interventions and post-surgical follow-up with imaging become more common. Computed tomography (CT) is the modality of choice in evaluating the patient with suspected aortic fistula because of its accessibility and short scan time. In addition, CT allows for more clear depiction of para-aortic or intra-aortic gas than ultrasound or magnetic resonance (MR). This gas may be the first clue of a fistula. Given the high mortality associated with aortic fistulae, familiarity with the imaging findings of the spectrum of aortic fistulae is essential knowledge in the emergency setting. This review will discuss the imaging appearance of aortic and arterial fistulae to the bronchi, esophagus, gastrointestinal tract, ureters, and veins on CT.