Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are unchanged compared to the prior study . The trachea is central . The cardiomediastinal contour is normal . A right internal jugular catheter terminates in the distal SVC . There is persistent visualization of a retrocardiac opacity which may reflect atelectasis , aspiration or pneumonia . This is similar in appearance when compared to the prior study . No pleural effusion seen . No pneumothorax seen .
    OUTPUT:
    
Persistent left basal retrocardiac opacity may reflect atelectasis , aspiration or pneumonia . Appearances are unchanged compared to the prior study .