Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: New patchy and linear opacities have developed in the left lower lobe , most marked in the retrocardiac area . Cardiomediastinal contours are stable in appearance , and there are no pleural effusions .
    OUTPUT:
    
Left lower lobe opacity , which could be due to atelectasis , aspiration or infectious pneumonia .