Aortic Fistulas to the Digestive and Respiratory Tracts

Introduction: Aortic fistulas are uncommon, but life-threatening abnormal connections that form between the aortoiliac vasculature and adjacent organs. The most common organs involved are the gastrointestinal tract, notably the esophagus and duodenum, and rarely the respiratory tract, notably the trachea. Aortic fistulas are classified as primary, which occur spontaneously from an underlying aneurysm, infection or inflammation, or secondary, which occur postoperatively from aortic wall erosion after surgical or endovascular grafting. The most common fistula type is a secondary fistula to the bowel that occurs after abdominal aortic aneurysm repair. Regardless of the location, aortic fistulas usually present with bleeding in the involved organ system and a visible tract on imaging. When this occurs, they are termed direct fistulas and often result in hemodynamic instability. However, rarely there can be occult fistulas seen on imaging without clinical bleeding and indirect fistulas that result in bleeding without a clear tract. Imaging diagnosis is best established with computed tomographic (CT) angiography with findings including gas in or around the aorta, aortic wall disruption, underlying aneurysm with or without stent-grafting, bowel or respiratory tract wall thickening, contrast extravasation, and general infectious or inflammatory changes around the aorta. However, catheter angiography, endoscopy, and ultrasound can aid in the diagnosis as well. Management of aortic fistulas requires initial resuscitation and hemodynamic support, antimicrobial therapy, and eventually aortic repair. Repair usually requires a very extensive open surgery, which has a high morbidity and mortality. However, endovascular techniques can be used in conjunction with surgery or alone as temporizing measures to remove the source of infection and control bleeding in patients who are poor surgical candidates. This includes removal of existing infected stent-grafts, aortic balloon occlusion, or fistula tract embolization. These endovascular techniques also have a high morbidity and mortality with outcomes dependent on the speed of diagnosis, comorbidities, and the presence or absence of infection. Unfortunately, due to the rarity of the condition substantial research is not available on management; however, there is emerging data trying to push treatment toward endovascular repair.

Content Organization:

• Introduction.

• Diagnosis.

• Management.

• Current literature.

• Cases.

• Research opportunities.

• Take home points.

Learning Points:

• Aortic fistulas are rare, but life-threatening

• Secondary fistulas from previously repaired abdominal aortic aneurysm to the bowel are more common than primary fistulas from underlying infection.

• Patients often present with direct bleeding through the fistula tract and are frequently unstable.

• Diagnosis is best made on CT angiography.

• Management can be done with open or endovascular repair with both having a high morbidity and mortality