Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest . There is subtle opacity at the left costophrenic angle with opacity also projecting in the posterior costophrenic sulcus on the lateral view . Elsewhere , the lungs are clear . Note is made of a fat pad at the right cardiophrenic angle similar to prior CT scan . The cardiomediastinal silhouette is within normal limits . No acute osseous abnormality is identified .
    OUTPUT:
    
Focal opacity at the left lung base , potentially infection in the proper clinical setting .