Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Minimal retrocardiac opacity these left lower lobe is likely from atelectasis due to volume loss . There is mild increased pulmonary venous pressure . No pleural abnormality is seen . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Minimal retrocardiac opacity , likely atelectasis . However , difficult to unequivocally exclude superimposed pneumonia .