Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is stable retrocardiac opacity that may reflect scarring / postsurgical change or atelectasis . The lungs and pleural spaces are otherwise clear without evidence of pneumothorax or pleural effusions . No focal consolidations are seen . The heart is within upper limits of normal in size . Mild degenerative change is present within the thoracic spine with some spurring . No acute fractures are seen .
    OUTPUT:
    
No acute intrathoracic process .