Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest are compared to previous exam from ___ . Previously identified left mid lung zone opacity has cleared . There is however new left basilar opacity which projects over the retrocardiac region on the lateral view . Given lower lung volume on the current exam particularly on the lateral this could be due to atelectasis however developing infiltrate is not excluded . Elsewhere the lungs are clear . Cardiomediastinal silhouette is within normal limits . Osseous and soft tissue structures are unremarkable .
    OUTPUT:
    
Increased opacity in the retrocardiac region on the lateral view likely localizing to the left . This could represent atelectasis given lower lung volume however developing consolidation from infection could be considered in the appropriate clinical setting .