Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs demonstrate slightly decreased lung volumes with prominence of the cardiac silhouette and bronchovascular crowding . Even allowing for this , the cardiac silhouette is likely top normal to mildly enlarged in size . A retrocardiac opacity likely represents pneumonia . There is no pleural effusion or pneumothorax . The visualized upper abdomen is unremarkable .
    OUTPUT:
    
Retrocardiac opacity , which likely represents pneumonia .