Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Mild cardiomegaly is persistent . The pulmonary arteries bilaterally , also demonstrate mild enlargement , consistent with pulmonary hypertension . There is no large pleural effusion , or pneumothorax . Subtle retrocardiac opacity is seen . There is mild bibasilar atelectasis . The visualized osseous structures are unremarkable .
    OUTPUT:
    
Subtle retrocardiac opacity may be secondary to pneumonia .