Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single frontal view of the chest demonstrates normal cardiomediastinal silhouette . The lung volumes are slightly low . There is a patchy opacity in the left lung base , probably representing atelectasis , although early infection can not be excluded in the appropriate clinical setting .
    OUTPUT:
    
Patchy opacity in the left lower lobe , which could represent subsegmental atelectasis versus subtle early infection in the appropriate clinical setting .