Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is of normal size with normal cardiomediastinal contours . Density projecting behind the heart is compatible with a moderate size hiatal hernia , similar to prior . Patchy retrocardiac opacity is compatible with atelectasis , although infection is not excluded . No pneumothorax . Osseous structures are unremarkable . No radiopaque foreign body .
    OUTPUT:
    
Patchy retrocardiac opacity compatible with atelectasis , although infection can not be excluded in the correct clinical setting .