Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . The heart continues to be enlarged with a left ventricular configuration . There is a left retrocardiac opacity which could reflect pneumonia versus atelectasis . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Cardiomegaly with left retrocardiac opacity possibly reflecting atelectasis versus pneumonia .