Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . Heart size is normal . Mediastinal and hilar contours are within normal limits . Crowding of the bronchovascular structures is demonstrated without pulmonary edema . Patchy opacities in the retrocardiac region may reflect atelectasis , but infection can not be completely excluded . No pleural effusion or pneumothorax is demonstrated . There are no acute osseous abnormalities .
    OUTPUT:
    
Patchy retrocardiac opacity , potentially atelectasis in the setting of low lung volumes , but infection can not be completely excluded .