Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle opacity at the lateral left lung base appears new since the prior study and may be due to a subtle pneumonia versus atelectasis . No pleural effusion is seen . There is no pneumothorax . The cardiac and mediastinal silhouettes are stable . No pulmonary edema is seen .
    OUTPUT:
    
No pulmonary edema . Subtle opacity over the lateral left lung base appears new since the prior study ; findings may be due to atelectasis or pneumonia .