Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded . There is a retrocardiac opacity which was not present in the prior exam . No other focal opacities are noted . Increased hilar prominence bilaterally may represent vascular congestion . Cardiomediastinal and hilar contours are unremarkable . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
1 . Retrocardiac opacity may represent left lower lobe peumonia versus atelectasis . 2 . Bilateral hilar prominence suggests fluid overload .