CONGENITAL LOBAR EMPHYSEMA
This is a rare
case of respiratory distress in the neonatal period. The overdistended lobe or
lobes cause compression of the remaining normal ipsilateral lung and a marked
shift of the mediastinum to the opposite side, so that a ventilatory crisis
results with dyspnea, cyanosis, and sometimes circulatory failure.
The pathogenesis of congenital lobar emphysema falls
into three categories. In the first group, there are defects in the bronchial
cartilage with absent or incomplete rings; the abnormality has also been
described in chondroectodermal dysplasia or Ellis-Van Creveld syndrome. In the
second group, there is an obvious mechanical cause of bronchial obstruction
such as a fold of mucous membrane acting as a ball valve, an aberrant artery or
fibrous band, tumors, or a tenacious mucous plug. In the third and largest
group, no local pathologic lesions other than overdistension of the lobe can be
seen, but unrecognized bronchiolitis has been thought to be a possible cause.
In each instance, the lobe inflates normally as the bronchus widens during
inspiration, but the obstruction to it during expiration results in air
trapping and overdistension.
The upper lobes are most commonly involved (80% of
cases), particularly on the left side (43% of cases); the right middle lobe
(32%) is second in order of frequency. Multilobar bilateral involvement rarely
occurs. Differential diagnosis from endobronchial pneumothorax, diaphragmatic
hernias, tension cysts, and endobronchial foreign bodies must be made.
One-third of patients are symptomatic at birth, and
approximately half are symptomatic in the first few days after birth. Affected
infants may have severe respiratory symptoms and a rapid deterioration,
resulting in death. Infants present with increasing dyspnea and recession;
cyanosis occurs in 50% of cases and is more obvious on crying. Only 5% of
patients are presented after 6 months of age. Physical examination reveals hyperresonance and bulging of the affected hemithorax
with a contralateral displacement of the trachea and mediastinum. Hyperlucency
of the diseased side is seen on radiography; the ribs are spread farther apart,
the diaphragm is lower than normal and flattened, and the uninvolved lobe or
lobes may be atelectatic. There is displacement of the mediastinum to the
opposite side where the lung appears relatively radiopaque, but the diaphragm
is not elevated as seen in atelectasis. In the involved lung, vascular markings may distinguish the abnormality from a
pneumothorax.
Lobectomy is indicated for patients who have
persistent or progressive respiratory failure, and early lobectomy is required
for infants who have significant respiratory distress in the neonatal period.
Patients presenting with relatively mild symptoms or diagnosed on chest
radiographic examination may be treated conservatively.
