Dr. Pepe’s Diploma Casebook: Case 117 – SOLVED!

Findings: PA radiograph shows a small right hemithorax with loss of volume and increased opacity of the right lung. The mediastinum is shifted towards the right (A, arrow) and there is elevation of the right hemidiaphragm, which is blurred in the lateral view (B, arrows).

Coronal CT confirms the right lung involvement and marked mediastinal shift (C, arrow). The patient had end-stage lung disease secondary to NSIP and had undergone a lung transplantation. MIP coronal reconstruction shows the area of suture of the left bronchus (D, arrow).

Final diagnosis: Small right lung due to NSIP. Transplanted left lung

I am presenting this case to discuss the small hemithorax, which is easily recognized because of its reduced size in comparison to the opposite side. Small hemithorax often shows partial or complete opacification of the underlying lung, pleural thickening, and crowding of the ribs.
The etiology of small hemithorax may be a pulmonary or pleural disease.

Lung-related causes of small hemithorax can be congenital or acquired. Among the congenital causes, the most frequent is hypoplasia/aplasia of the lung and bronchial tree (Fig. 1). Much less common is congenital unilateral absence of the pulmonary artery or pulmonary veins (Fig. 2).

Acquired causes of small hemithorax can be obstruction of the main bronchus of any etiology (Fig. 3) (malignant endobronchial tumor being the most common), or a chronic pulmonary infection, with lung destruction and volume loss (most commonly due to TB) (Fig. 4).

Coronal CT confirms the left lung volume loss and the endobronchial lesion (C, arrow). Bronchoscopy extracted thick mucus from the left main bronchus. A post-procedure radiograph shows re-expansion of most of the left lung with residual LUL collapse (D, arrow). Diagnosis: allergic aspergillosis

Pleural disease may cause small hemithorax by creating a thick cuirass that impedes expansion of the lung and decreases the size of the affected hemithorax. Most causes of benign pleural thickening result from empyema or a hemothorax, which often become calcified (Fig. 5).

Malignant pleural mesothelioma may grow in a plaque-like manner and encase the lung, causing a decrease in size of the hemithorax (Fig. 6). Metastasis to the pleura can give a similar appearance (Fig. 7).

Last, but not least, we have to consider previous surgery as the cause of small hemithorax. The most frequent etiology is lung resection (Fig. 8), but a rib cage intervention should also be considered (Fig. 9).

Thoracoplasty is an old procedure, mainly used in the pre-antibiotic era to collapse tuberculous cavities. We still see some of these patients (Fig. 9).

Follow Dr. Pepe’s advice:

1. Congenital small hemithorax is usually due to hypoplasia of the lung.

2. The most common cause of acquired small hemithorax is an endobronchial lesion.

3. Chronic pleural disease is not an uncommon cause of small hemithorax.