Pneumonectomy with compensatory hyperinflation
This patient had a right pneumonectomy for lung cancer. The unusual lucency (arrows) projected over the right hemithorax on this follow-up CXR actually represents part of the left lung, which has hyperinflated to compensate for the volume loss in the right hemithorax. This compensatory hyperinflation can develop as a result of any cause of severe volume loss in the contralateral loss, such as bronchial obstruction or extensive fibrosis. Following pneumonectomy, the space left behind by the resected lung gradually fills in with fluid, elevation of the hemidiaphragm and compensatory hyperinflation. The hemithorax also reduces in size due to a reduction in the space between the ribs on that side (nicely demonstrated in this example).