SEVERAL entities can lead to localized pulmonary lucencies appearing on pediatric chest roentgenograms. Most are acquired abnormalities, since congenital lung cysts are rare, even in the pediatric age group. Inflammatory processes are the principal cause of acquired pulmonary cysts, with trauma being less common. Pneumatocele, lung abscess, and cavitating pneumonia fall into the category of acquired lesions. At times, the radiological appearance of these abnormalities can be prominent and even dramatic.
Abscesses characteristically occur during the course of bacterial infections. Klebsiella and staphylococcal pneumonia predominate but Escherichia coli and group B Streptococcus may be the offending organisms in neonates.1 Pulmonary abscess may also develop in Haemophilus influenzae pneumonia, tuberculosis, and aspiration pneumonitis when bacteria are involved. An abscess typically evolves slowly while the patient is extremely ill. The cavity appears to have ill-defined borders and thick walls because of surrounding infiltrate. Several points of bronchial communication are