Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal and hilar contours are within normal limits . A retrocardiac opacity correlates with a subtle haziness projecting over the posterior lung bases on the lateral view . There is no pneumothorax , fracture or dislocation . Limited assessment of the abdomen is unremarkable .
    OUTPUT:
    
A retrocardiac opacity at the left lung base is concerning for pneumonia .