Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral radiographs of the chest demonstrate mild asymmetric opacity at the left base which may represent atelectasis . Left upper lobe scarring is unchanged . Additionally , there is a minimal left pleural effusion . No definite rib fracture is identified . The remainder of the lungs are clear and the cardiac and mediastinal contour is within normal limits .
    OUTPUT:
    
Mild asymmetrical opacity at the left base which may represent atelectasis . Small left pleural effusion .