Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Retrocardiac opacity is increasing . The left diaphragmatic contour remains blunted . Aortic arch calcifications are similar . No new consolidation or pneumothorax is present . Mild thoracolumbar scoliosis is unchanged .
    OUTPUT:
    
Increasing retrocardiac opacity likely represents atelectasis rather than consolidation .