The computed tomographic characteristics of the pleural empyema were illustrated in three patients. A typical empyema is characterized by lower thorax location, oblong or round contour in cross-section, homogeneous content with or without air spaces or air-fluid levels, regularly thin wall opposing the chest wall (a rim sign), irregularly thick wall opposing the lung parenchyma, and smooth inner and outer margins. By application of such computed tomographic criteria, a pleural empyema can be readily distinguished from a peripheral lung abscess. © 1983.
