Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single AP upright portable chest radiograph demonstrates several healed fractures involving the right ribs . Opacity at the left lung base may reflect atelectasis or alternatively scarring . An early pneumonia can not be excluded . The remaining lungs are clear . Cardiomediastinal and hilar contours are within normal limits allowing for patient positioning .
    OUTPUT:
    
Opacity at the left lung base may reflect atelectasis or alternatively scarring . In the appropriate clinical setting , early pneumonia can not be excluded .