Thoracic radiology: pulmonary patterns
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This is a short review of pulmonary patterns.
Interstitial pattern:
can be structured versus non structured.
The structured pattern is further divided to milliary (distinct structures which are smaller than 5mm) and nodular (the structures are larger than 5 mm). Pulmonary masses are interstitial. Click here to view an example of milliary pattern.
Non structured interstitial pattern is characterized by increased lung opacity and a decrease in the visualization of the pulmonary vessels.
Obesity, expiration films and under exposure will also result in increased lung opacity.
Non structured interstitial pattern results from the presence of cellular infiltrates (neoplastic, inflammatory, hemorrhagic), fibrosis or fluids within the lung parenchyma. When becomes severe, it develops into alveolar pattern.
When the pattern observed is mainly interstitial a lung aspiration or biopsy is required in order to characterize the pathology.
Bonchial pattern
This pattern results from accumulation of fluid or cells around the bronchial walls. It is characterized by thickening of the bronchial walls which appears like tram lines (longitudinal view) or donuts (end-on). Donuts are easier to recognize.
Bronchoalveolar lavage and trans tracheal wash can aid in the diagnosis.
An example of a bronchial pattern:
An 11 year old cat with chronic asthma.
Note the diffuse broncho-interstitial pattern
Click on the image below to view full size
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Alveolar pattern
This pattern is characterized by air bronchogram and when severe enough a lobar sign will be seen as well.
When the amount of the fluid/cellular infiltrates in the interstitium is overzealous and the interstitium is full, there is air left only in the bronchi. In this case we will see air bronchograms which are a complete silhouette sign of the airway's wall.
A lobar sign is a sharp line of demarcation between an opaque (consolidated) lung lobe and adjacent aerated lung lobe.
Bobcho-alveolar lavage and transtracheal wash can be used to characterize the fluid.
In the example below there are airbronchograms and a lobar sign associated with the left cranial lung lobe. Those are visible over the cardiac silhouette.
Click on the image to view full size
