Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal contours are mildly exaggerated secondary to low lung volumes , otherwise are unremarkable . New retrocardiac opacity may be due to pneumonia or atelectasis . There is persistent blunting of the right costophrenic angle . There is no evidence of a pneumothorax .
    OUTPUT:
    
New retrocardiac opacity may be due to pneumonia or atelectasis , given low lung volumes .