Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart is mildly enlarged ; however , stable compared to the prior exam . The mediastinal contours are unremarkable . The lung volumes are low . There is a new focal opacity at the left lung base concerning for infection . There is mild right basilar atelectasis . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
New focal opacity at the left lung base concerning for pneumonia , versus atelectasis .