Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . The heart is of normal size with normal cardiomediastinal contours . Subsegmental atelectasis is seen at the left lung base . No pulmonary consolidation , pleural effusion , or pneumothorax . Pulmonary vasculature is unremarkable . Osseous structures are unremarkable . No radiopaque foreign body .
    OUTPUT:
    
Left lung base subsegmental atelectasis .