• Etymology

  • Derived from the words air, referring to gaseous content, and bronchogram, originating from the Greek words bronchos (windpipe) and gramma (writing or representation), referring to the radiological depiction of air-filled bronchi.

  AKA

  • Bronchial aeration sign

  Definition

  • What is it? Air bronchogram refers to the radiological appearance of air-filled bronchi outlined by surrounding areas of alveolar consolidation, atelectasis, or other pathological opacification.
  • Caused by:
    • Alveolar filling processes such as pneumonia, pulmonary edema, or hemorrhage.
    • Surrounding tissue collapse due to atelectasis or mass effect.
    • Surfactant deficiency
  • Resulting in:
    • Structural changes: Air-filled bronchi become visible against the background of non-aerated lung tissue.  This may be due to consolidation or ground glass changes, or surround atelectasis
    • Pathophysiology: Air within bronchi persists while adjacent alveoli are filled with fluid, pus, blood, or cells, or are otherwise non-aerated.
    • Pathology: Preservation of bronchial patency despite the surrounding opacification.
  • Diagnosis:
    • Clinical: Often associated with symptoms of underlying lung pathology, such as fever, dyspnea, or cough, depending on the cause.
    • Radiology: Visible on chest X-ray (CXR) and CT as air-filled tubular structures within areas of increased lung opacity.
    • Labs: Findings depend on the underlying etiology, such as elevated inflammatory markers in infection or reduced oxygenation in pulmonary edema.
  • Treatment: Directed toward the underlying cause, such as antibiotics for infection, diuretics for pulmonary edema, or other disease-specific therapies.

  Radiology

  • CXR
    • Findings: Linear or branching air-filled structures (bronchi) visible within areas of increased lung density.
    • Associated Findings: May include consolidation, atelectasis, or other patterns of lung opacity.
  • CT
    • Parts: Visible as branching, air-filled bronchi within consolidated or otherwise non-aerated lung parenchyma.
    • Size: Reflects the bronchial anatomy in the affected region.
    • Shape: Tubular or branching.
    • Position: Located within consolidated, atelectatic, or otherwise opacified lung tissue.
    • Character: Well-defined air-filled structures surrounded by dense lung parenchyma.
    • Time: Can be transient or persistent, depending on the cause.
    • Associated Findings: May include ground-glass opacities, nodules, or other features of the underlying disease.
  • Other Imaging Modalities
    • Rarely evaluated with MRI; ultrasound may show air reverberation artifacts in consolidation.

  Key Points and Pearls

  • The presence of air bronchograms strongly suggests patency of the bronchi and rules out complete airway obstruction.
  • Commonly associated with alveolar processes such as pneumonia, pulmonary edema, or hemorrhage.
  • Air bronchograms can occur in atelectasis including compressive atelectasis when atelectasis is caused by compression from external forces and from adhesive atelectasis when there is collapse secondary to ARDS and deficiency of surfactant
  • A critical radiological sign for differentiating between various lung pathologies and guiding appropriate treatment.

It is Black and White

When Things are Different,
Especially When They Are Total Opposites –
They Each Become Much Clearer

CT Scan of Air Bronchograms
Secondary to Bacterial Pneumonia
in the Lingula

 

Multifocal Pneumonia with
Air Bronchograms Exemplified in the
Right Lower Lung Zone in the
Middle Lobe on CXR

On Closer Inspection
Prominent Air Bronchograms in the
Left Lower Lobe (behind the heart)
Also Upper Lobes (less obvious)

CT Scan of Air Bronchograms
Secondary to Bacterial Pneumonia in the Lingula

 

Chronic Eosinophillic Pneumonia
Upper Lobe Peripheral Consolidations with
Air Bronchograms

Lobar

Segmental

Subsegmental

 

Radiopaedia

“Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not be visible if the bronchi themselves are opacified (e.g. by fluid) and thus indicate patent proximal airways.

Air bronchograms can be seen with several processes:

• pulmonary consolidation
• pulmonary edema: especially with alveolar edema ³
• non-obstructive atelectasis
• severe interstitial lung disease
• neoplasms: bronchioloalveolar carcinoma; pulmonary lymphoma
• pulmonary infarct
• pulmonary hemorrhage
• normal expiration

Air bronchograms that persist for weeks despite appropriate antimicrobial therapy should raise the suspicion of a neoplastic process. CT may be planned in such cases.”