Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . There is mild left base atelectasis . Retrocardiac density with subtle suggestion of air - fluid level on the lateral view , most likely represents a hiatal hernia , correlate with history of hiatal hernia . The aorta is calcified and tortuous . The cardiac silhouette is not enlarged .
    OUTPUT:
    
Clear lungs . Retrocardiac density with suggestion of air - fluid level on the lateral view most likely represents a hiatal hernia .