Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is at the upper limits of normal , likely exaggerated by AP technique . The mediastinal contours demonstrate a prominent right upper contour and a lack of a left - sided aortic knob , suggestive of a right - sided aorta , confirmed on localizer images from ___ spinal MR . ___ hilar contours are within normal limits . The lung volumes are low with bibasilar opacities , most compatible with atelectasis , although underlying pneumonia can not be entirely excluded . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
1 . Probable bibasilar atelectasis , although in the appropriate clinical setting , pneumonia must be considered . 2 . Right - sided aortic arch .