Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single chest AP radiograph demonstrates a calcified , tortuous aorta . Otherwise , the mediastinal , hilar , and cardiac contours are unremarkable . A very faint opacity in the left lower lung likely represents atelectasis , though in the appropriate clinical setting can not exclude early pneumonia . No pleural effusion or pneumothorax evident .
    OUTPUT:
    
Faint left base opacity represents most likely atelectasis but an early pneumonia can not be excluded in appropriate clinical setting .