Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable view of the chest is compared to previous exam from ___ . There is elevation of the right hemidiaphragm as on prior . There is more dense retrocardiac opacity seen on the current exam when compared to prior , which raises the possibility of pneumonia or aspiration . Streaky right basilar opacity may be due to atelectasis . Superiorly , the lungs are clear . Cardiomediastinal silhouette is within normal limits . Left shoulder arthroplasty again noted .
    OUTPUT:
    
Retrocardiac opacity , potentially due to pneumonia versus aspiration .