Air Bronchogram Definition
An air bronchogram is a radiologic sign defined by visualization of air-filled bronchi within an area of airless lung (e.g., consolidation or atelectasis). [1]
Typical Imaging Appearance
On chest radiography, an air bronchogram appears as branching lucent (dark) tubular structures coursing through a region of increased opacity from surrounding air-space consolidation. [2] On CT, an air bronchogram appears as air-filled bronchial structures within consolidation or within an atelectatic airless parenchymal background. [1]
Typical Anatomic Location on Imaging
The air bronchogram is typically observed in the lung parenchyma affected by air-space disease, rather than in normally aerated lung where bronchi are usually not visible on standard radiographs. [2] When present, the sign localizes to the same region as the underlying consolidation or atelectasis on the image. [1]
Common Clinical Context
Air bronchograms are commonly associated with conditions that fill alveolar spaces around patent bronchi, such as pneumonia. [2]
Key Differentiating Feature
Air bronchograms indicate that bronchi within the area of abnormal lung remain air-filled and patent while surrounding alveoli are airless. [1]