Computed tomography of lung abscess and empyema

Lung abscess and empyema can often be distinguished on plain radiographs. Sometimes, oblique or decubitus views may be necessary in order to demonstrate the more specific conventional radiographic features--the shape of the lesion and its relationship to the chest wall. In seriously ill patients, special positioning may be impossible. CT may be easier to perform than special views in some ill patients. In many cases of suppurative disease, both lung and pleura may be involved, and pleural disease in the presence of lung disease is easily missed on plain radiographs. Furthermore, infections located at the periphery or at the apices of the thorax are difficult to define with conventional imaging. CT with cross-sectional images and unequalled density resolution delineates the lung-pleura interface and the periphery and apices of the lung. With CT, lung abscess and empyema show statistically significant differences in shape--round (abscess) or lenticular (empyema); the presence of separation of pleural layers (empyema); the presence of lung compression (empyema); the presence of acute (abscess) or obtuse (empyema) chest wall angles; and wall characteristics--thick, nonuniform, and irregular (abscess) or thin, uniform, and smooth (empyema). Few lesions demonstrate all of these features; however, sufficient information may be obtained from CT to permit a confident diagnosis of lung abscess or empyema. Thus, CT helps in the evaluation of suppurative diseases. CT provides diagnostic information not available from conventional radiographs in 47 per cent of cases, and in 34 per cent of cases, CT gives more accurate delineation of the extent of disease.(ABSTRACT TRUNCATED AT 250 WORDS)