Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal and hilar contours are within normal limits . The aorta is minimally tortuous . There is a retrocardiac opacity as well as mild opacity seen at the base of the right lung . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Retrocardiac and right basal opacity may represent atelectasis or infection in the appropriate clinical setting .