The definitive evaluation of a child with a suspected congenital cystic abnormality of the tracheobronchial tree is best done using which of the following?

b. Computerized tomography or magnetic resonance imaging

Plain film radiography is the first imaging study performed and remains a cornerstone for the diagnosis and follow-up of this group of lesions. The use of additional imaging provides definitive diagnosis and allows planning for the surgical approach as well. Computed tomography (CT) and magnetic resonance imaging (MRI) can separate cystic from solid components in a radiopaque lung mass. These are the most definitive diagnostic studies available. The MRI has reconstructive capabilities that obviate the need for angiography. Intravenous contrast with CT scan provides similar anatomic information. Ultrasonography is less costly, more readily performed and in select cases may be as sensitive. Angiography is not employed regularly because these alternative imaging strategies provide similar information at lower cost with less morbidity. A barium esophagogram is helpful in the diagnosis of children with dysphagia but that is a rare presentation for these lesions. Bronchoscopy is rarely helpful for these lesions and in these infants and small children carries the risk of general anesthesia and positive pressure ventilation. In children with congenital lobar emphysema and cystic adenomatoid malformation, hyperinflation following positive pressure may induce mediastinal compression and create a surgical emergency. For these reasons, CT or MRI are considered the best definitive diagnostic imaging choices after the initial chest x-ray.