Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright chest radiograph provided . There is significant volume of free air below both right and left hemidiaphragm . There is basilar atelectasis . Otherwise , lungs are clear . Cardiomediastinal silhouette is normal . Bony structures appear intact .
    OUTPUT:
    
Large volume pneumoperitoneum . Please refer to outside hospital CT exam for further details .