Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . Mediastinal and hilar contours are unremarkable , and the pulmonary vasculature is normal . Apart from mild atelectasis in the left lung base , no focal consolidation , pleural effusion or pneumothorax is present . No acute osseous abnormalities demonstrated . There are mild degenerative changes in the thoracic spine .
    OUTPUT:
    
Mild left basilar atelectasis .