congenital lobar overinflation
Congenital lobar overinflation (CLO), previously called congenital lobar emphysema, is a congenital lung abnormality that results in progressive overinflation of one or more lobes of a neonate's lung.
On imaging, it classically presents on chest radiographs as a hyperlucent lung segment with overinflation and contralateral mediastinal shift.
Congenital lobar overinflation is more common in males (M: F = 3:1).
Patients typically present with respiratory distress, most commonly in the neonatal period, and usually within the first six months of life .
In congenital lobar overinflation, a lobe (or more) becomes distended and may or may not have an overabundance of alveoli. There are many presumed mechanisms for progressive overdistension of a lobe, including obstruction, cartilage deficiency, dysplasia, and immaturity . Most cases are idiopathic.
Interestingly, there is a pronounced predilection for certain lobes:
- left upper lobe: most common, 40-45%
- right middle lobe: 30%
- right upper lobe: 20%
- involving more than a single lobe: 5%
- much rarer in the lower lobes
Therefore, although the left upper lobe is most commonly affected, the right hemithorax is more commonly affected than the left .
Immediate postpartum period
The affected lobe tends to appear opaque and homogeneous because of fetal lung fluid or it may show a diffuse reticular pattern that represents distended lymphatic channels filled with fetal lung fluid.
- appears as an area of hyperlucency in the lung with oligemia (i.e. paucity of vessels)
- mass effect with mediastinal shift and hemidiaphragmatic depression
- lateral decubitus film with the patient lying on the affected side will show little or no change in lung volume
- lateral film may show posterior displacement of the heart
CT is usually performed to confirm the diagnosis, evaluate the mediastinal vascular structures, and to rule out other abnormalities.
- shows above features in greater detail
- attenuation of vascular structures in affected lobe
- may also show compressive atelectasis of adjacent lobes
Treatment and prognosis
General imaging differential considerations include:
- bronchial atresia: the parenchyma distal to the atretic segment can have air trapping
- congenital pulmonary airway malformation (CPAM)
- pulmonary arterial hypoplasia
- pulmonary hypoplasia
- Swyer-James syndrome
- filamin A mutation
- differential for unilateral transradiant hemithorax