Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest provided . Lung volumes are low . Retrocardiac opacity is noted which could reflect the presence of known hiatal hernia . No convincing signs of pneumonia or edema . No large effusion or pneumothorax . The heart appears mildly enlarged . Aortic calcification is noted . The mediastinal contour is unchanged . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
Retrocardiac opacity likely reflects known hiatal hernia . Mild cardiomegaly .