Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A single portable frontal chest radiograph was obtained . Subcutaneous emphysema in the right and left lateral margins of the chest and lower cervical regions is extensive . An air - filled retrocardiac structure is similar to the pre-operative appearance of the large hiatal hernia . The cardiac silhouette is widened by AP portable technique .
    OUTPUT:
    
1 . Extensive subcutaneous emphysema .