Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior exam , lung volumes are slightly lower . Slight interval increase in left infrahilar opacity may reflect developing atelectasis . Elevation of the left hemidiaphragm is unchanged . Mild right basilar atelectasis . Aortic knob calcifications are similar the prior exam . No pneumothorax . No pleural effusion . Heart size is difficult to assess . Nonspecific gaseous distension of visualized bowel loops in the left upper quadrant .
    OUTPUT:
    
Subtle increased opacity in the left infrahilar region could reflect atelectasis .