Asymmetric radiographic findings in the pediatric chest: approach to early diagnosis.

Several conditions in children produce a mass effect within one hemithorax, which may be life threatening. The different radiographic appearances of these conditions provide a basis on which they can be classified. The three major categories include a large cystic hemithorax, a large lucent hemithorax, and a large opaque hemithorax. Some disorders may be seen within more than one major group. Within the large cystic hemithorax group, congenital cystic adenomatoid malformation and congenital diaphragmatic hernia may be life-threatening conditions that require emergency surgery. The large lucent hemithorax is usually caused by pneumothorax, partial bronchial occlusion, or compensatory hyperinflation of the unobstructed lung. The majority of cases within the large opaque hemithorax group involve pleural fluid collections. Because many conditions that cause a mass effect require intervention or surgery, accurate interpretation of the plain chest radiograph is essential for an early diagnosis. Classification of radiographic features into these three groups often allows accurate diagnosis without additional studies.