Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is top normal . The hilar and mediastinal contours are within normal limits . Chronic cephalization of the pulmonary markings is seen , however , there is no overt pulmonary edema present . There may be small bilateral pleural effusions . There is no evidence of a pneumothorax . There is a subtle opacity at the left lung base , which may be secondary to atelectasis ; however , an acute infectious process can not be excluded .
    OUTPUT:
    
No definite evidence of pulmonary edema . Subtle increased opacity at the left lung base may be secondary to atelectasis ; however , a superimposed infectious process can not be excluded .