Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Slight interval increase in the degree of left retrocardiac airspace opacity , which may represent worsening atelectasis versus consolidation . The right lung is grossly clear . No pleural effusion or pneumothorax . The cardiomediastinal silhouette is unchanged .
    OUTPUT:
    
Slight increase in left basilar retrocardiac airspace opacity , likely representing atelectasis versus pneumonia .