Congenital lobar overinflation is a rare fetal developmental anomaly of the lungs. It is also termed congenital lobar emphysema, characterized by air entering the lungs, but due to an obstruction in the airways, air cannot leave the lungs, leading to an enlarged, overinflated lung lobe. It is also sometimes associated with congenital heart defects such as ventricular septal defect, patent ductus arteriosus, and tetralogy of Fallot. It is most commonly seen in neonatal or early infancy and rarely seen in adults. It has a male predilection over females with a 3:1 ratio.

Each lung is divided into two or three sections, known as lobes. The right lung is divided into three lobes, whereas the left is divided into two lobes only. The left upper lobe is affected mostly by almost 40 %, followed by the right middle lobe at 34 % and the right upper lobe at 21 %. The involvement of the lower lobe is rare and present in only 2 % of the cases.

The affected lobe becomes non-functional due to overdistention and air trapping. Due to the severity of the symptoms, it is often diagnosed within the first six months of birth. The overinflated lobes thereby cause impaired ventilation and perfusion. The increased overinflation causes compression of adjacent organs and ultimately causes respiratory failure and death.

What Is the Cause of Congenital Lobar Overinflation?

Congenital lobar overinflation can be due to the followings:

Idiopathic or unknown causes in 50 % of the cases.
Absence of bronchial cartilage. Hypoplasia or dysplasia.
Parenchymal diseases.
External bronchial obstruction.
Internal bronchial obstruction.

What Is the Histopathology Behind Congenital Lobar Overinflation?

There is no destruction of the alveolar walls and septum with normal acini, but acinar maturation with age and overinflated alveoli are seen.

There is no tissue destruction, as seen in the case of emphysema. It has two forms:

What Are the Types of Congenital Lobar Overinflation?

There are two types of congenital lobar overinflation:

Intrinsic congenital lobar overinflation.
Extrinsic congenital lobar overinflation.

Intrinsic Congenital Lobar Overinflation: It occurs when there is an obstruction from within. For example, an abnormal airway obstruction.

Extrinsic Congenital Lobar Overinflation: It occurs when there is a compression of the airways due to nearby abnormal structures, such as a bronchogenic cyst.

What Are the Signs and Symptoms of Congenital Lobar Overinflation?

The signs and symptoms include

Shortness of breath or dyspnea.
Rapid breathing or tachypnea.
Enlarged chest due to overinflation involving at least one lung lobe.
Cyanosis - bluish discoloration of the skin.
Wheezing.
Increased heart rate or tachycardia.
Respiratory distress.
Underdevelopment of cartilage that supports the Bronchial tube.

What Are the Diagnostic Tests for Congenital Lobar Emphysema?

The Diagnostic test involves

Chest X-ray.
Computed tomography (CT) scan.
Fetal Ultrasound.
Fetal magnetic resonance imaging.

Chest X-ray: The affected lobes show overinflation and hyperlucency with oligemia or paucity of vessels. The lateral film may show posterior displacement of the heart. Mass effect with mediastinal shift and hemidiaphragmatic depression is also seen. A lateral decubitus film with the patient lying on the affected side may show little or no change in the lung volume.

CT Scan: It is the standard gold method to diagnose congenital lobar emphysema. It attenuates vascular structures in the affected lobe and may also show compressive atelectasis of adjacent lobes. It helps in evaluating the affected lobe from the normal structures. A single photon emission technology combined with a CT scan can be used to evaluate the perfusion ventilation ratio in affected lobes. A CT, along with injectable intravenous contrast, helps to evaluate the vascular anomalies in congenital lobar emphysema.

Fetal Ultrasound: The lungs of the fetus show hyperechogenicity with or without mediastinal shift.

What Is the Treatment Modality?

The severity of the disease defines the treatment modality. Patients with mild to moderate symptoms can be treated conservatively with regular follow-up and observation, whereas lobectomy or surgical removal of the affected lobe is preferred with severe symptoms. The conservative approach has become popular due to antenatal diagnosis and intrauterine regression.

What Are the Differential Diagnosis of Congenital Lobar Overinflation?

The differential diagnosis includes

Bronchial atresia.
Pulmonary hypoplasia.
Congenital pulmonary airway malformation (CPAM).
Pulmonary arterial hypoplasia.
Swyer- James syndrome.
Filamin A mutation.
Pneumothorax.
Pneumonia.

Bronchial atresia is typically seen with obliterated proximal segments of the bronchus associated with hyperinflation of the distal lung. Air trapping can be seen in the parenchyma distal to the atretic segment.

Congenital pulmonary airway malformation and congenital lobar emphysema typically show similar features on ultrasound with high echogenic masses. Also, congenital lobar emphysema has no cystic spaces compared to congenital pulmonary airway malformation.

Pneumonia in the affected lungs in chest X-ray shows consolidations which improve on taking antibiotics. There is no overinflation seen in cases of pneumonia.

Filamin A gene produces filamin protein, which helps build the internal network of protein filaments known as the cytoskeleton. The cytoskeleton gives cellular structure and allows them the flexibility to change shape. It leads to skeletal dysplasia, cardiovascular abnormalities, and otopalatodigital spectrum disorders and is also associated with lung diseases.

How Is the Prognosis of the Disease?

Mild to moderate cases can be managed easily with a conservative approach, whereas severe cases require lobectomy. The prognosis of the disease is excellent, and mortality is quite low.

What Are the Complications?

The complications include:

Cyanosis.
Surgical complications.
Respiratory failure.
Infantile death.

Conclusion:

To conclude, congenital lobar overinflation is a rare developmental anomaly of the lungs in infants characterized by overinflation of one or more lobes leading to compression of lung parenchyma and displacement of mediastinal structures.

It usually presents with cyanosis, rhonchi (airway sound), wheezing, and difficulty in breathing. The diagnosis is made based on the clinical examination and imaging findings. Computed tomography of the lungs is considered the gold standard for diagnosing congenital lobar overinflation. The best treatment for a severe case is lobectomy or lobar resection. The prognosis of the disease is excellent, and mortality is quite low.