Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is at the upper limits of normal size . There is no pleural effusion or pneumothorax . There is vague opacity obscuring the left cardiac margin , probably within the lingula . Elsewhere , the lungs appear clear . Old remodeled fractures involve the posterior lateral third through fifth ribs on the left only .
    OUTPUT:
    
Patchy lingular opacity ; differential considerations include atelectasis or potentially pneumonia .