Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . Mediastinal and hilar contours are unremarkable . There is mild calcification of the aortic arch . There is no pulmonary vascular congestion . Patchy opacities within the left lung base are nonspecific but could reflect areas of atelectasis or infection . Blunting of the costophrenic angle on the left posteriorly suggests a trace pleural effusion . There is no pneumothorax . No acute osseous abnormalities are seen .
    OUTPUT:
    
Patchy opacity in the left lung base could reflect an area of infection or atelectasis with probable small left pleural effusion .