Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a small left pleural effusion , which is decreased as compared to the ___ radiograph . A rounded opacity in the left mid lung may have been previously obscured by the pleural effusion , and may correspond to known pleural metastasis or new infection . Biapical pleural scarring is unchanged . The right lung is clear . There is no pneumothorax . The heart and mediastinum are within normal limits .
    OUTPUT:
    
Decreased small left pleural effusion . Rounded opacity in the left mid lung may be due to infection or known pleural metastases .