Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiograph demonstrate increased retrocardiac opacification new since prior examination concerning for infection . The right lung is clear with no convincing opacity concerning for pneumonia . Blunting of bilateral costophrenic angles is unchanged when compared to prior examination and may represent pleural thickening . The cardiomediastinal and hilar contours are stable in appearance . Osseous structures demonstrates no acute abnormality .
    OUTPUT:
    
Retrocardiac opacity , new since prior examination , which could be pneumonia . Recommend repeat after treatment to document resolution .