Air bronchogram
Updates to Article Attributes
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 oedema: especially with alveolar oedema 3
non-obstructive atelectasis
severe interstitial lung disease
neoplasms: bronchioloalveolar carcinoma; pulmonary lymphoma
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.
Radiographic features
Ultrasound
Sonographic air bronchograms arise as a secondary consequence of an extreme perturbation of the air-fluid relationship in the lung parenchyma, in which fluid-filled alveoli act as an excellent acoustic medium and allow visualisation of the lung parenchyma. Arborising tubular structures representing the bronchial tree may be visualised which, when patent, appear to contain punctiform-to-linear foci. These structures may remain fixed in position throughout the respiratory cycle or be observed to propagate distally and proximally with inspiration and expiration, respectively. This distinction is important for determining the aetiology of the underlying pathology 4;
-
dynamic air bronchograms move centrifugally with respiration
represent fluid mixed with air inside larger bronchi, which are in continuity with the gas inspired by the patient
indicates a non-retractile consolidation, ruling out resorption atelectasis
the specificity of 94% and a positive predictive value of 97% for pneumonia as the cause of the consolidation
-
static air bronchograms lack detectable movement
indicate isolated, trapped air, consistent with resorptive atelectasis
HRCT
Consolidation refers to the accumulation of fluid, exudate or cellular material in lung parenchyma, resulting in a decreased aeration of lung tissue. On high-resolution computed tomography (HRCT), consolidation appears as areas of increased density, with a hazy or homogeneous appearance. The imaging findings of alveolar filling consolidation depend on the underlying cause and the stage of the disease process.
Acute alveolar filling consolidation is commonly caused by infections such as pneumonia, which results in an accumulation of inflammatory exudate in the alveolar spaces. On HRCT, the consolidations appear as hazy, homogeneous opacities that may have an air-bronchogram. The air-bronchogram refers to the presence of air within airways within an area of consolidation, and is seen when the airway walls are still visible within the area of fluid accumulation.
Chronic alveolar filling consolidations may result from lymphoma, bronchovascular carcinoma, tuberculosis, and infarcts. On HRCT, these consolidations are usually more dense and have a lower likelihood of having an air-bronchogram. The opacities may become confluent, meaning they merge together to form larger areas of decreased density.
Pseudoalveolar filling consolidations are opacities that mimic alveolar filling but are caused by different mechanisms such as lipoid pneumonia or silicosis. On HRCT, pseudoalveolar opacities may have a different pattern than true alveolar filling opacities, with a more nodular or irregular appearance.
History and etymology
The term air bronchogram was coined by Ben Felson (1913-1988) 5.
See also
-<p><strong>Air bronchogram</strong> 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.</p><p>Air bronchograms can be seen with several processes:</p><ul>-<li><a href="/articles/air-space-opacification-1">pulmonary consolidation </a></li>-<li>-<a href="/articles/pulmonary-oedema">pulmonary oedema</a>: especially with <a href="/articles/pulmonary-alveolaroedema">alveolar oedema</a> <sup>3</sup>-</li>-<li>non-obstructive <a href="/articles/atelectasis">atelectasis</a>-</li>-<li>severe <a href="/articles/interstitial-lung-disease">interstitial lung disease </a>-</li>-<li>neoplasms: <a href="/articles/broncholoalveolar-carcinoma">bronchioloalveolar carcinoma</a>; <a href="/articles/pulmonary-lymphoma">pulmonary lymphoma</a>-</li>-<li><a href="/articles/pulmonary-infarct">pulmonary infarct</a></li>-<li><a href="/articles/pulmonary-haemorrhage">pulmonary haemorrhage</a></li>-<li>normal expiration</li>-</ul><p>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.</p><h4>Radiographic features</h4><h5>Ultrasound</h5><p>Sonographic air bronchograms arise as a secondary consequence of an extreme perturbation of the air-fluid relationship in the lung parenchyma, in which fluid-filled alveoli act as an excellent acoustic medium and allow visualisation of the lung parenchyma. Arborising tubular structures representing the bronchial tree may be visualised which, when patent, appear to contain punctiform-to-linear foci. These structures may remain fixed in position throughout the respiratory cycle or be observed to propagate distally and proximally with inspiration and expiration, respectively. This distinction is important for determining the aetiology of the underlying pathology <sup>4</sup>;</p><ul>-<li>dynamic air bronchograms move centrifugally with respiration<ul>-<li>represent fluid mixed with air inside larger bronchi, which are in continuity with the gas inspired by the patient</li>-<li>indicates a non-retractile consolidation, ruling out resorption atelectasis</li>-<li>the specificity of 94% and a positive predictive value of 97% for pneumonia as the cause of the consolidation</li>-</ul>-</li>-<li>static air bronchograms lack detectable movement <ul><li>indicate isolated, trapped air, consistent with resorptive atelectasis</li></ul>-</li>-</ul><h4>History and etymology</h4><p>The term air bronchogram was coined by <a href="/articles/benjamin-felson">Ben Felson</a> (1913-1988) <sup>5</sup>.</p><h4>See also</h4><ul><li><a href="/articles/air-space-disease">airspace disease</a></li></ul>- +<p><strong>Air bronchogram</strong> 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.</p><p>Air bronchograms can be seen with several processes:</p><ul>
- +<li><p><a href="/articles/air-space-opacification-1">pulmonary consolidation</a></p></li>
- +<li><p><a href="/articles/pulmonary-oedema">pulmonary oedema</a>: especially with <a href="/articles/pulmonary-alveolaroedema">alveolar oedema</a> <sup>3</sup></p></li>
- +<li><p>non-obstructive <a href="/articles/atelectasis">atelectasis</a></p></li>
- +<li><p>severe <a href="/articles/interstitial-lung-disease">interstitial lung disease</a></p></li>
- +<li><p>neoplasms: <a href="/articles/broncholoalveolar-carcinoma">bronchioloalveolar carcinoma</a>; <a href="/articles/pulmonary-lymphoma">pulmonary lymphoma</a></p></li>
- +<li><p><a href="/articles/pulmonary-infarct">pulmonary infarct</a></p></li>
- +<li><p><a href="/articles/pulmonary-haemorrhage">pulmonary haemorrhage</a></p></li>
- +<li><p>normal expiration</p></li>
- +</ul><p>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.</p><h4>Radiographic features</h4><h5>Ultrasound</h5><p>Sonographic air bronchograms arise as a secondary consequence of an extreme perturbation of the air-fluid relationship in the lung parenchyma, in which fluid-filled alveoli act as an excellent acoustic medium and allow visualisation of the lung parenchyma. Arborising tubular structures representing the bronchial tree may be visualised which, when patent, appear to contain punctiform-to-linear foci. These structures may remain fixed in position throughout the respiratory cycle or be observed to propagate distally and proximally with inspiration and expiration, respectively. This distinction is important for determining the aetiology of the underlying pathology <sup>4</sup>;</p><ul>
- +<li>
- +<p>dynamic air bronchograms move centrifugally with respiration</p>
- +<ul>
- +<li><p>represent fluid mixed with air inside larger bronchi, which are in continuity with the gas inspired by the patient</p></li>
- +<li><p>indicates a non-retractile consolidation, ruling out resorption atelectasis</p></li>
- +<li><p>the specificity of 94% and a positive predictive value of 97% for pneumonia as the cause of the consolidation</p></li>
- +</ul>
- +</li>
- +<li>
- +<p>static air bronchograms lack detectable movement </p>
- +<ul><li><p>indicate isolated, trapped air, consistent with resorptive atelectasis</p></li></ul>
- +</li>
- +</ul><h5>HRCT</h5><p>Consolidation refers to the accumulation of fluid, exudate or cellular material in lung parenchyma, resulting in a decreased aeration of lung tissue. On high-resolution computed tomography (HRCT), consolidation appears as areas of increased density, with a hazy or homogeneous appearance. The imaging findings of alveolar filling consolidation depend on the underlying cause and the stage of the disease process.</p><p>Acute alveolar filling consolidation is commonly caused by infections such as pneumonia, which results in an accumulation of inflammatory exudate in the alveolar spaces. On HRCT, the consolidations appear as hazy, homogeneous opacities that may have an air-bronchogram. The air-bronchogram refers to the presence of air within airways within an area of consolidation, and is seen when the airway walls are still visible within the area of fluid accumulation.</p><p>Chronic alveolar filling consolidations may result from lymphoma, bronchovascular carcinoma, tuberculosis, and infarcts. On HRCT, these consolidations are usually more dense and have a lower likelihood of having an air-bronchogram. The opacities may become confluent, meaning they merge together to form larger areas of decreased density.</p><p>Pseudoalveolar filling consolidations are opacities that mimic alveolar filling but are caused by different mechanisms such as lipoid pneumonia or silicosis. On HRCT, pseudoalveolar opacities may have a different pattern than true alveolar filling opacities, with a more nodular or irregular appearance.</p><h4>History and etymology</h4><p>The term air bronchogram was coined by <a href="/articles/benjamin-felson">Ben Felson</a> (1913-1988) <sup>5</sup>.</p><h4>See also</h4><ul><li><p><a href="/articles/air-space-disease">airspace disease</a></p></li></ul>
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