Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Chest PA and lateral radiographs demonstrate unremarkable mediastinal , hilar , and cardiac contours . Low lung volumes causing mild vascular crowding at the lung bases , otherwise , lungs are clear . Rounded opacification with air - fluid in retrocardiac space likely corresponds with moderate - to - large hiatal hernia present on the ___ abdominal CT .
    OUTPUT:
    
Large hiatal hernia . No acute cardiopulmonary process .