Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart is top normal size and cardiomediastinal silhouette is stable . A well - defined rounded retrocardiac opacity containing an air - fluid level is consistent with known hiatal hernia . There is mild bibasilar atelectasis . No focal consolidation , pleural effusion or pneumothorax .
    OUTPUT:
    
No evidence of pneumonia .