Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP chest radiograph . The left lung base is chronically opacified , likely due to combination of a pericardial fat pad and scarring as shown on prior CT . The lungs are otherwise clear . There is no pleural effusion or pneumothorax . The cardiomediastinal silhouette is stable . There is a chronic fracture of the right lateral sixth rib .
    OUTPUT:
    
No acute cardiopulmonary process .