Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . There is a retrocardiac posterior lower lobe opacity more readily appreciated on the lateral view . The lungs are otherwise clear . The hilar and cardiomediastinal contours are normal . There is crowding of the pulmonary vasculature due to incomplete inspiration .
    OUTPUT:
    
Retrocardiac opacity best appreciated on the lateral view which may represent early pneumonia in the appropriate clinical setting .