Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: On the lateral view is increased opacity at the posterior costophrenic angle , not clearly localized to the left of the right based on the frontal view . Elsewhere , the lungs are clear . The cardiomediastinal silhouette is within normal limits . No acute osseous abnormality .
    OUTPUT:
    
Opacity projecting over the posterior costophrenic angle variably present on prior exams potentially atelectasis or scarring noting that infection can not be excluded . If treatment is planned , followup after course of antibiotics is suggested to document resolution . If not compatible with pneumonia clinically , CT scan is suggested to further characterize .