Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable supine view of the chest was provided . There is irregular opacity at the left lung base which could represent a very early pneumonia versus atelectasis / scarring . The lungs appear lucent in the upper lobes , likely reflecting emphysema . Cardiomediastinal silhouette appears normal . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
Subtle reticular opacities in the left lower lung likely represent scarring / atelectasis , though pneumonia is not excluded . Probable underlying emphysema .