Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right IJ catheter tip projects over the expected region of the proximal right atrium , unchanged . Lung volumes remain low . Asymmetric appearance of the lungs has resolved , likely reflecting rotation on the prior exam and asymmetric edema . However , mild left lower lobe opacity persists , suggesting atelectasis . No pneumothorax . No large effusion .
    OUTPUT:
    
Mild left lower lobe atelectasis .