Fig. 50.1
Chest x-ray showing congenital lobar emphysema involving the left upper lobe. Note the mediastinal shift and herniation of the affected lobe to the other side with compression on the contralateral lung
Congenital cardiac anomalies may be present in as many as 10 % of patients with CLE. All patients with CLE should have adequate preoperative cardiac evaluation by echocardiography.
CLE commonly occur in whites.
CLE appears to be more common in males than females. The male-to-female ratio is 3:1.
Sites
CLE primarily involves one lobe of the lung (upper lobes are predominantly involved) as follows:
Left upper lobe, 40–42 %.
Right middle lobe, 34–35 %.
Right upper lobe, 20–21 %.
Involvement of the lower lobes is rare, occurring in fewer than 5 % of patients.
Bilateral involvement in 20 %.
Pathogenesis
CLE is characterized by progressive lobar hyperinflation that commonly results from disruption in bronchopulmonary embryological development .
These result from abnormal embryological interactions between embryonic endodermal and mesodermal components of the lung.
These disturbances may lead to changes in the number of airways or alveoli or abnormalities in alveolar size. Based on this, CLE is divided into two forms:
Hypo alveolar: Characterized by fewer than expected number of alveoli.
Polyalveolar: Characterized by greater than expected number of alveoli.
The exact cause of CLE is not known and several factors have been incriminated. These include:
Intrinsic absence or abnormality of cartilaginous rings (deficiency in the cartilage of the bronchial wall). This is seen in 50–60 % of these cases.
Extra luminal obstruction and compression of the affected bronchus by abnormal blood vessel (as in the absence of the pulmonary valve) or congenital lung cyst. This leads to emphysema from partial obstruction.
Congenital bronchial stenosis and redundant bronchial mucosal flaps.
Polyalveolar lobe (the alveolar size may be normal, but the alveolar number is increased three- to fivefold). This leads to hyperexpansion of the affected pulmonary lobe .
All of these factors lead to a ball-valve effect that permits inflation of the affected lobe during periods of negative intrathoracic pressure, but collapses and obstructs the affected bronchus with expiration. Ultimately, this leads to air trapping and overexpansion of the affected lobe of the lung.
CLE should be differentiated from the Swyer–James syndrome (i.e., acquired pulmonary abnormality secondary to infection leading to small but hyperlucent lung).
A mucous plug which can obstruct a bronchus, creating a “check-valve” phenomenon that partially obstructs an airway should be excluded .
Associated Malformations
Associated congenital malformations are seen in 14–21 % of patients with CLE .
Congenital heart disease (PDA, VSD) is the commonest.
Of those with congenital heart disease, 10 % have additional anomalies including:
Rib cage defects
Renal anomalies
Clinical Features
Most patients with CLE present before 6 months of life with recurrent respiratory distress. Half of the cases of CLE present within the first 4 weeks of life and three-quarters are seen in infants less than 6 months of life .
The presentation of CLE in relation to age is as follows:
At birth: 33 %
By 1 month of age: 50 %
After 6 months of age: 5 %
Although the majority of patients with CLE present early as an acute neonatal respiratory distress, a small group of them may be asymptomatic or present at a later age with recurrent chest infection.
Neonates commonly present with mild-to-moderate respiratory distress.
This is associated with mediastinal shift, hyperresonance, and decreased breath sounds on the affected side.
Infants usually present with cough, wheezing, respiratory distress, and cyanosis.
Older children with CLE may present with recurrent chest infections.
The severity of CLE is variable as follows:
Most patients present with moderate respiratory distress.
Cyanosis in half of the patients.
Less than half present with mild respiratory distress.
CLE can be asymptomatic discovered incidentally on chest x-ray.
Rarely, CLE presents with severe life-threatening respiratory distress .
Diagnosis
CLE is most often detected in neonates or identified during in utero ultrasound which shows the affected lobe as an overinflated, fluid-filled lobe associated with mediastinal herniation .
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