Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest . There is subtle increased opacity in the left mid lung which projects in the retrosternal clear space on the lateral view . Elsewhere , the lungs are clear . There is no pneumothorax or effusion . The cardiomediastinal silhouette is within normal limits . No acute osseous abnormality is identified . Surgical clips in the right upper quadrant suggest prior cholecystectomy .
    OUTPUT:
    
Subtle left mid lung opacity which could represent atelectasis although infection is possible in the proper clinical setting .