Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are moderately well expanded . Opacity in the left lung base , consistent with previously described chronic atelectasis , although can not exclude a superimposed pneumonia or infection in the right clinical setting . There is a small left pleural effusion , which appears increased from prior exam . There is no right pleural effusion . The cardiomediastinal silhouette is enlarged , similar prior exam . There are degenerative changes of the thoracic spine .
    OUTPUT:
    
Left lung base opacity , consistent with previously described chronic atelectasis although can not exclude a superimposed pneumonia affection the right clinical setting , particularly with the increased left pleural effusion .