Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal contours are unchanged . The lungs demonstrate improved vascular congestion . In the retrocardiac region , there is a rounded density which is confirmed on the lateral view , compatible with a hiatal hernia . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Retrocardiac opacity represents hiatal hernia .