Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are very low . Retrocardiac opacities could be due to atelectasis or pneumonia in the right clinical setting . Widened mediastinal contours and cardiomegaly are likely accentuated by AP technique . Pulmonary edema is mild . A left pleural effusion is small .
    OUTPUT:
    
Retrocardiac opacities could be due to atelectasis or pneumonia .