Congenital Lobar Emphysema

Congenital lobar emphysema refers to progressive hyperinflaction of a lobe due to a check-valve mechanism at the bronchial level. There is no destruction of alveolar walls and the majority of cases are idiopathic. Malacia or stenosis of the bronchial cartilage can be seen in patients and are thought to represent possible etiologies. Cardiovascular anomalies can be seen in about 15% of cases.

The most commonly affected lobe is the left upper lobe (40%), followed by the right middle (35%) and upper (20%) lobes. The lower lobes are less commonly affected.

Most patients present before 6 months of age, most commonly with respiratory distress. Three clinical types can be defined based on the age of presentation: infancy (type I, most common), older children (type II, rare), or incidental in asymptomatic patients (type III, rare).

Chest radiographs obtained during the neonatal period may reveal the affected lobe to be opaque (because of retained fetal lung fluid) or diffusely reticular (due to distended lymphatic channels filled with fetal lung fluid). As the fluid clears by absorption, the affected lung progresses from alveolar opacification to interstitial reticulation to hyperlucency.

Mass effect from the expanded lobe or segment can compress adjacent lobes and structures, sometimes causing ipsilateral or contralateral atelectasis. The adjacent lobe collapses either caudad or cephalad but not medially. The ipsilateral rib spaces may be widened, the ipsilateral hemidiaphragm may be depressed, and there may be contralateral mediastinal shift.

Differential considerations for the hyperlucent lung include pneumothorax, lung cysts (simple or acquired), foreign body with air trapping, and pulmonary sling (only vascular ring associated with asymmetric lung aeration).

The images above show an opacity in the right lung that progressively clears to result in a hyperexpanded right lung that causes compression of the adjacent lung and contralateral mediastinal shift by 6 months. Chest radiograph at 2 years of age reveals a hyperexpanded right hemithorax with widening of the intercostal spaces and leftward mediastinal shift.

References

Berrocal T, Madrid C, Novo S, Gutiérrez J, Arjonilla A, Gómez-León N. Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology. Radiographics. 2004 Jan-Feb;24(1):e17.