Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal silhouette is within normal limits . Low volume lungs are clear . There is no pleural effusion or pneumothorax . Retrocardiac opacity is likely related to atelectasis from low lung volumes . Lungs and the upper abdomen are grossly unremarkable .
    OUTPUT:
    
No evidence of pneumonia .