Mechanisms of Bullae Formation: the bullae may be simple airspaces or may retain the trabeculations of the emphysematous lung
Coalescence of Adjacent Areas of Emphysematous Lung
Locally Severe Panacinar Emphysema
Ball-Valve Effect in Bronchus Supplying an Emphysematous Region of Lung
Clinical Manifestations
Asymptomatic
Most bullae are clinically asymptomatic
Bullitis (Infected Bullae)
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Example
Clinical History: 82 y/o WM with active tobacco abuse, congestive heart failure, pulmonary hypertension, and home O2-dependent bullous emphysema who was admitted with COPD exacerbation and pneumonia with bullitis (sputum and blood cultures were negative in this case)
Radiologic Features
Note air-fluid levels within the bullae
Note the emphysematous changes in the surrounding right lung, consistent with severe underlying emphysema
Also note that the patient had a pre-existing bullae in this location prior to the infection, making the diagnosis of necrotizing pneumonia with cavitation (which can appear similarly) less likely