Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiographs demonstrate clear lungs bilaterally . Linear opacity at the base of the left lung is most likely atelectatic in etiology . Cardiomediastinal and hilar contours are within normal limits . There is no pneumothorax , evidence of pulmonary edema , or pleural effusion . No free air under the right hemidiaphragm is identified .
    OUTPUT:
    
No acute intrathoracic abnormality .