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 lung. Various mechanisms have been postulated including an obstructive check valve mechanism at the bronchial level 2.


Congenital lobar overinflation is more common in males (M:F = 3:1) 5.

Clinical presentation

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. Most cases are idiopathic.


CLO may be associated an aberrant left pulmonary artery 7 and also with congenital heart defects:

Radiographic features

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.

Plain radiograph
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.

Later findings
  • 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
  • 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.

Differential diagnosis

General imaging differential considerations include:

See also

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