Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patchy left base opacity is seen , which could be due to atelectasis although pneumonia is not excluded in the appropriate clinical setting . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Patchy left base opacity , which is subtle , could be due to atelectasis although pneumonia is not excluded in the appropriate clinical setting .