Emphysema Paraseptal emphysema 2021-02-24T12:52:39Z Paraseptal emphysema is characterized by predominant involvement of the distal alveoli and their ducts and sacs. It is characteristically bounded by any pleural surface and the interlobular septa. This emphysema is characterized by subpleural and peribronchovascular regions of low attenuation separated by intact interlobular septa, sometimes associated with bullae. See Figure 47 of Hansell DM, et al., Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246:697-722. Distal acinar emphysema