Pneumonia. Pearls for interpreting patients' radiographs

The chest radiograph can detect pneumonia, but laboratory evaluation is needed to determine the specific causative organism. However, before these results become available, a presumptive diagnosis can be made with the help of chest radiography. A lobar pattern on radiography is usually produced by pneumococcal and Klebsiella infections. A lobular (bronchopneumonia) pattern may be produced by Staphylococcus, gram-negative organisms, and anaerobes. An interstitial pattern results from viral, Mycoplasma, and Pneumocystis carinii infections. Mixed patterns may also occur. There is great variation in the presentation of each infection. However, pertinent clinical information, epidemiologic factors, and associated radiographic findings (eg, adenopathy, pleural effusion, cavitation) are helpful in further limiting diagnostic possibilities.