Role of conventional chest radiography in diagnosis and exclusion of emphysema.

Although recognizing that the subject is controversial, most authors of textbooks about diagnostic radiology conclude that chest radiography is of little value for either confirmation or exclusion of the diagnosis of emphysema. Yet several reports in the literature show a high degree of accuracy in the interpretation of films for presence of this disease. Some of the controversy results from continuing confusion over the current definition of emphysema in terms of lung structure rather than symptoms or physiologic evidence relating to impaired ventilation. Many autopsy studies have shown that emphysema is often present at postmortem examination and can involve as much as 30 percent of the lung tissue, even in subjects with no respiratory symptoms or impairment during life. Since radiographs deal with structure rather than function, interpreters of chest films should have the intention to recognize the presence of structural emphysema. The correct recognition of emphysema is useful even in a patient without symptoms, and the ability to exclude this diagnosis in symptomatic patients is of equal, if not greater value. The degree of success reported in various studies depends upon the criteria used and the strictness applied by the authors in matching their interpretations to the presence or absence of structural emphysema. This review of existing literature deals solely with papers in which radiographic observations have been related to morphologic evidence of emphysema in inflation-fixed autopsy lung specimens. It identifies reasons for discrepancies among reports and emphasizes the very high predictive value of validated radiographic criteria. Applications of radiographic interpretation both for diagnosis and for exclusion of emphysema in clinical situations are described.