Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is retrocardiac opacification , localized to the lower lobe on the lateral , which may represent atelectasis , but is concerning for an early / developing pneumonia . The heart is mildly enlarged , which may be projectional . There is pulmonary vascular congestion , but no frank pulmonary edema . Probable small left pleural effusion . No pneumothorax .
    OUTPUT:
    
1 . Left lower lobe retrocardiac opacification , which may represent atelectasis , but is concerning for an early / developing pneumonia . 2 . Pulmonary vascular congestion with a small left pleural effusion .