When Air is a Red Herring: Benign Appearances of Air in Unusual Locations

In the emergency radiology setting, ectopic air can frequently be a cause for alarm, such as with pneumothorax, pneumomediastinum, and portal venous gas. Ectopic air can often serve as a harbinger of serious injury, which can prompt the radiologist to notify clinicians so patients can receive appropriate care. However, there are many benign conditions which may present radiographically with air in unusual locations. It is critical to be able to recognize these benign entities, as inaccurate identification could lead to unnecessary procedures or imaging. We present numerous benign conditions which can produce air in unusual locations that we have encountered in our practice. For each condition, we will describe its etiology and will also provide key imaging findings that help to distinguish it from pathology.