Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a focal opacity in the left lower lung , partially obscuring the left cardiac silhouette . The lungs are otherwise clear . There is a large amount of relative lucency within the left lung , which is suggestive of emphysema . The hilar and cardiomediastinal contours are normal . There is no pneumothorax or large pleural effusion . Pulmonary vascularity is normal .
    OUTPUT:
    
Subtle opacity of the left lower lung abutting the left heart border which may represent an early lingular pneumonia . Please refer to subsequent CTA chest for additional details .