Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac , mediastinal and hilar contours . Pulmonary vasculature is normal . Patchy opacity is noted within the left lower lobe , possibly atelectasis but early infection is not excluded . The right lung is clear . There is no pleural effusion or pneumothorax is present . No acute osseous abnormality is demonstrated .
    OUTPUT:
    
Patchy opacity in the left lower lobe , possibly atelectasis though infection can not be excluded .