Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is mildly enlarged . There is no pneumothorax or pleural effusion . Bibasilar linear opacities likely reflect atelectasis , though a left basilar retrocardiac opacity with small air bronchograms may reflect a small underlying consolidation , difficult to differentiate from focal atelectasis . There is persistent elevation of left hemidiaphragm . The central pulmonary vessels are engorged , without overt edema .
    OUTPUT:
    
Small retrocardiac opacity at the left base may represent a small consolidation , versus focal atelectasis .