Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest provided demonstrate a retrocardiac opacity which could represent a hiatal hernia . The lungs appear clear without focal consolidation , effusion , or pneumothorax . The cardiomediastinal silhouette appears normal . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
Retrocardiac opacity which is most compatible with a hiatal hernia .