Air-bronchogram (summary)

This is a basic article for medical students and other non-radiologists

Air-bronchograms are gas-filled bronchi surrounded by alveoli filled with fluid, pus or other material . It is a very useful sign because it is highly sensitive and specific for the presence of lung consolidation rather than collapse.

Reference article

This is a summary article; read more in our article on air bronchogram.

Summary

• pathophysiology
  • gas-filled bronchus surrounded by abnormal lung
    • pus/fluid/cells/blood within the alveolar spaces
    • collapse adjacent to the bronchus
• role of imaging
  • determine the cause of adjacent opacification
    • air-space opacification (consolidation)
    • atelectasis (collapse) tends not to have air bronchograms
    • pleural fluid does not have air bronchograms
  • determine whether there are any associated complications
    • underlying cause
    • identify pleural effusion
    • identify cavitation

Radiographic features

Chest radiograph

A bronchus filled with gas does not attenuate x-rays as they pass through the thorax. As such, they appear black (or at least very dark) on radiograph or CT. In a normal lung the bronchi are surrounded by alveoli that are also filled with gas, and therefore are virtually indistinguishable.

However, when there is fluid material in the surrounding alveoli, this abnormal accumulation attenuates x-rays and so the lung appears dense or white. This is what we call air-space opacification. The bronchi running through this area are now clearly seen as gas-filled tubes coursing through a solid-appearing area of the lung.

Air-bronchograms are more commonly seen in consolidation than collapse although their presence does not exclude collapse.

CT Chest

Computer tomography uses x-rays to build up a multislice picture of a section of anatomy. As such, the imaging findings are similar to a radiograph - we just see them in much more detail.