Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiograph demonstrate linear opacity at the left lung base , present on examination dated ___ , likely atelectatic in etiology . No opacity convincing for pneumonia is present . Cardiomediastinal and hilar contours are stable relative to prior examination , the cardiac silhouette mildly enlarged . Pulmonary vasculature is normal . There is no pneumothorax or pleural effusion . There is no evidence of pulmonary edema .
    OUTPUT:
    
No acute intrathoracic abnormality .