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) 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) become distended and may or may not have more 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 quite a pronounced predilection for some lobes:
- left upper lobe: most common, 40-45%
- right middle lobe: 30%
- right upper lobe: 20%
- may involve more than a single lobe: 5%
- much rarer in the lower lobes
Therefore despite the left upper lobe being most commonly affected, the right hemithorax is the most common side to be affected 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 a paucity of vessels
- mass effect with mediastinal shift and hemidiaphragmatic depression
- decubitus films lying on the affected side will show little or no change in lung volume
- lateral film may demonstrate 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 neighbouring lobes
Treatment and prognosis
Mildly symptomatic patients are usually followed up. A lobectomy can be considered in severe cases 3.
General imaging differential considerations include:
- congenital cystic adenomatoid malformation (CCAM) / congenital pulmonary airway malformation (CPAM)
- pulmonary arterial hypoplasia
- pulmonary hypoplasia
- bronchial atresia: the distal to the atretic segment can have air trapping
- 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
- 3. Man DW, Hamdy MH, Hendry GM et-al. Congenital lobar emphysema: problems in diagnosis and management. Arch. Dis. Child. 1983;58 (9): 709-12. doi:10.1136/adc.58.9.709 - Free text at pubmed - Pubmed citation
- 4. Daltro P, Fricke BL, Kuroki I et-al. CT of congenital lung lesions in pediatric patients. AJR Am J Roentgenol. 2004;183 (5): 1497-506. AJR Am J Roentgenol (full text) - Pubmed citation
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- 6. Stigers KB, Woodring JH, Kanga JF. The clinical and imaging spectrum of findings in patients with congenital lobar emphysema. Pediatr. Pulmonol. 1992;14 (3): 160-70. - Pubmed citation
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