Aortic Fistulas: Pathophysiologic Features, Imaging Findings, and Diagnostic Pitfalls

Fistulas between the aorta and surrounding organs are extremely rare but can be fatal if they are not identified and treated promptly. Most of these fistulas are associated with a history of trauma or vascular intervention. However, spontaneous aortic fistulas (AoFs) can develop in patients with weakened vasculature, which can be due to advanced atherosclerotic disease, collagen-vascular disease, vasculitides, and/or hematogenous infections. The clinical features of AoFs are often nonspecific, with patients presenting with bleeding manifestations, back or abdominal pain, fever, and shock. Confirmation with invasive endoscopy is often impractical in the acute setting. Imaging plays an important role in the management of AoFs, and multiphasic multidetector CT angiography is the initial imaging examination of choice. Obvious signs of AoF include intravenous contrast material extravasation into the fistulizing hollow organ, tract visualization, and aortic graft migration into the adjacent structure. However, nonspecific indirect signs such as loss of fat planes and ectopic foci of gas are seen more commonly. These indirect signs can be confused with other entities such as infection and postoperative changes. Management may involve complex and staged surgical procedures, depending on the patient's clinical status, site of the fistula, presence of infection, and anticipated tissue friability. As endovascular interventions become more common, radiologists will need to have a high index of suspicion for this entity in patients who have a history of aneurysms, vascular repair, or trauma and present with bleeding. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. ^©RSNA, 2021.

Aorto-left atrial fistula: Rare cause of acute cardiac failure in a previously healthy individual

Complications of valvular infective endocarditis involving the peri-annular region puts the patient at a significantly high risk of adverse outcomes including heart failure and death. The "mitral-aortic intervalvular fibrosa" is relatively avascular and offers little resistance to the spread of abscesses, aneurysm, and fistula formation. Aorto-cavitary fistulous tract formation in the setting of native valve infective endocarditis is associated with higher rates of heart failure, ventricular septal defect, and atrioventricular block than nonruptured abscesses. Thus, a high index of suspicion is needed for rapid and accurate diagnosis, which can guide further management. A transesophageal echocardiogram is the preferred modality of investigation in such cases. Staphylococci are reported to be the most common pathogen involved. In addition to early antibiotic therapy, prompt surgical intervention might save lives in these scenarios.