Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided pacemaker device is noted with leads terminating in the right atrium and right ventricle . Moderate enlargement of cardiac silhouette is re - demonstrated . The aortic knob is calcified . Mediastinal and hilar contours are unchanged . Pulmonary vasculature is not engorged . Patchy retrocardiac opacity may reflect an area of atelectasis . No focal consolidation , pleural effusion or pneumothorax is present . No acute osseous abnormality is detected . Multiple clips are visualized within the right upper quadrant of the abdomen .
    OUTPUT:
    
Retrocardiac patchy opacity , likely atelectasis .