Congenital lobar overinflation
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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) 5.
Patients typically present with respiratory distress, most commonly in the neonatal period, and usually within the first six months of life 5.
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 2. 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 6.
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 4
- 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
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- 2. Berrocal T, Madrid C, Novo S et-al. Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology. Radiographics. 24 (1): e17. doi:10.1148/rg.e17 - Pubmed citation
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