Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . Heart size is normal . Mediastinal and hilar contours are unremarkable . There is no pulmonary edema . Small left pleural effusion is noted with associated left basilar opacity , possibly compressive atelectasis though infection can not be excluded . Right lung is clear . No pneumothorax is identified . No acute osseous abnormalities are seen .
    OUTPUT:
    
Small left pleural effusion with adjacent left basilar opacity , possibly reflecting compressive atelectasis though infection is not excluded .