Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single AP upright view of the chest was reviewed and compared to the prior study . Lung volumes are low and there has been interval increase in a retrocardiac opacity since ___ as well as increased opacifications at both lung bases , particularly the left lung base that could be atelectasis with or without pneumonia . Normal heart , mediastinal and pleural surfaces .
    OUTPUT:
    
Bibasilar and retrocardiac opacities have been increasing since ___ due to atelectasis with or without pneumonia .