Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is no significant change and decreased volume and left basal opacity consistent with left lower lobe collapse . Bilateral small pleural effusions are unchanged with subsegmental right basilar atelectasis . The pulmonary vasculature is normal . The cardiac and mediastinal contours are notable for enlargement of the aortic knob contour , consistent with known dissection . Retrocardiac opacity likely reflect a combination of atelectasis and known large hiatal hernia .
    OUTPUT:
    
1 . Unchanged left lower lobe collapse . 2 . Abnormal aortic knob contour , consistent with patient 's known aortic dissection is not enlarging .