What is an air bronchogram?
In a normal chest radiograph, the air-filled bronchi are not distinguishable from the surrounding air-filled alveoli. If the alveoli become consolidated, then there is an attenuation difference between the air-filled bronchi and the surrounding fluid-filled alveoli. As a result, one or more bronchi become visible as dark branching lines within the opacified lung. This phenomenon is termed an “air bronchogram.” The presence of an air bronchogram is a specific marker of airspace lung disease