Differentiating empyemas and peripheral pulmonary abscesses: the value of computed tomography.

In 13 patients, conventional radiographic techniques and clinical histories were not sufficient to determine whether a peripheral cavitary lesion was an abscess or an empyema. However, after computed tomography (CT), eight patients were diagnosed as having abscesses and five as having empyemas. Abscesses had an irregular shape and a relatively thick wall which was not uniformly wide and did not have a discrete boundary between the lesion and lung parenchyma. In contrast, empyemas had a regularly shaped lumen, a smooth inner surface, and a sharply defined border between the lesion and lung. CT studies can help to distinguish between empyemas and abscesses, and treatment can be started sooner in difficult cases.