Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are slightly reduced , with the heart size appearing borderline enlarged . The mediastinal and hilar contours are unremarkable , and there is no pulmonary vascular engorgement . Streaky opacity within the left lung base may reflect atelectasis , but infection can not be completely excluded . There is no pleural effusion or pneumothorax . No acute osseous abnormalities are detected .
    OUTPUT:
    
Slightly decreased lung volumes with streaky left basilar opacity , possibly reflecting atelectasis , but infection can not be excluded .