Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Pediatric sternal wires are present . A prosthetic cardiac valve is unchanged in configuration . The heart size is top - normal . The aortic arch is moderately calcified . There is no pneumothorax or pleural effusion . The central pulmonary vessels are prominent , without edema or congestion . There persistent left retrocardiac opacity is again seen , slightly more exaggerated on the current examination due to lower lung volumes , likely reflecting atelectasis , although underlying consolidation can not be entirely excluded .
    OUTPUT:
    
Minimal change since the ___ chest radiograph . Persistent left retrocardiac opacity is difficult to differentiate between atelectasis and small consolidation .