Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a left retrocardiac opacity , possibly representing pneumonia based on clinical presentation , less likely atelectasis . There is a small left pleural effusion . Cardiomediastinal silhouette and hila are normal . There is no pneumothorax .
    OUTPUT:
    
Left retrocardiac opacity might represent pneumonia given context . Atelectasis considered given volume loss .