Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well - expanded . There is an elevated left hemi-diaphragm . There is a retrocardiac opacity which may represent atelectasis , but can not exclude pneumonia or aspiration in the right clinical setting . No pleural effusion or pneumothorax is seen . There is mild to moderate cardiomegaly , similar prior exam . Left - sided subcutaneous gas may be related to recent VATS .
    OUTPUT:
    
Retrocardiac opacity which may represent atelectasis or post procedure changes , but can not exclude pneumonia or aspiration in the right clinical setting