Discussion
The association of congenital heart defects and congenital lobar emphysema is well known, and the large left to right shunts are commonly associated with CHD. Though, Tetralogy of Fallot (TOF) and other right to left shunts are seen sometimes6. Cough, tachypnea, and respiratory distress in early infancy are the usual clinical presentation in both conditions; CLE and left to right shunts. It is quite possible in clinical practice, that CHD being much more commoner is suspected and diagnosed first. Then, the entire clinical constellation is attributed to the CHD and the presence of CLE is only detected after correction of the CHD. Similar cases have been reported in the past6,7.
The etiology of CLE remains unknown in almost half of the cases. Absent or dysplastic bronchial cartilage is evident in one-fourth of the cases. Internal obstruction or external compression of the lobar bronchus due to various causes is postulated in the remaining cases. These defects cause ball valve effect and air trapping during the expiration with progressive hyperinflation of the affected lobe. The hyperinflated lobe may compress the surrounding normal lobes. In extreme cases, the hyperinflated lobe can herniate to the surrounding lobes as well as to the opposite thoracic cavity with tracheal and mediastinal shifts. This reduces the respiratory reserve and causes ventilation/perfusion mismatch with resultant hypoxia1,3.
In the embryo, the development of the bronchial cartilage occurs during 4 to 6th intrauterine weeks. This time coincides with an important developmental stage of cardiac chamber septation. Thus, the defect during this stage can affect both the heart and lungs1. Many a time, CLE is secondary to bronchial compression due to aberrant or dilated pulmonary vessels owing to pulmonary hypertension in presence of a large left to right shunt. In this case, CLE may get self-resolved on correction of underlying CHD5,6.
CLE continues to pose a diagnostic dilemma. The first diagnostic modality is the X-ray chest. The affected lung lobe is hyperlucent with atelectasis of the adjacent lung lobes due to compression. As well, a mediastinal shift can be seen. Though, all the features are not evident on X-ray at an early age. X-ray findings are often misreported as pneumonia owing to the crowding of the surrounding lobes, and the affected lobe hyperlucency may get reported as a pneumothorax. Computed Tomography (CT scan) of the lung is confirmatory and delineates anatomical details. Bronchoscopy may aid the diagnosis when the internal bronchial obstruction is suspected1-4.
Treatment of CLE is the surgical resection of the affected lobe. Conservative management is proposed for older children having no or minimal symptoms.But the infants with persistent distress are the ideal candidates for the surgery. Surgery is by far well tolerated with low mortality and favorable outcomes2,8. In the case of concomitant CLE and CHD, there are diverging views in the management as to what to repair first, or a combined lung and cardiac repair would be the ideal approach. An individualized approach has been suggested. Many a time, CLE gets corrected with the relaxation of the vascular compression on the repair of the large left to right shunt and reduction of pulmonary hypertension5,9.
In our case, the child presented with respiratory distress. During the stay, clinical suspicion leads us to perform 2D Echocardiography which revealed a large VSD with moderate PDA with PAH. The presence of a congenital defect of the lung was overshadowed by the presence of a large heart defect. The symptoms were obviously contributed to the heart defect.The X-ray finding was interpreted as pneumonia initially. We may see in Figure 1 (two months of age) that there is no obvious hyperlucency of the right middle lobe, rather haziness is evident in the right upper lobe. In contrast, later X-ray, Figure 2 (seven months of age) clearly demonstrated a large hyperlucent area in the right middle lobe with surrounding lobe crowding and mediastinal shift.In retrospect, we could make out the faint hyperlucency in Figure 1, which was initially missed out.We believe that the X-ray chest being a basic investigation is often given less attention, particularly when the other advent diagnostic modality has suggested alternative diagnosis.
Congenital lobar emphysema is a diagnostic challenge, and the confusion can be further augmented in the presence of an obvious large congenital heart defect. A close look over the chest X-ray may give the lead, but the CT scan is a confirmatory investigation. Regular follow-up and a high index of suspicion are necessary for early diagnosis. Lobectomy can lead to dramatic improvement and is well tolerated.