Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP semi-upright view of the chest demonstrates low lung volumes . Linear opacity in the right lung base likely represents atelectasis . Small left pleural effusion is unchanged . There is no right pleural effusion or pneumothorax . Hilar and mediastinal silhouettes are unchanged . Heart size is normal . Right - sided chest tube is in unchanged position . Partially imaged upper abdomen is unremarkable .
    OUTPUT:
    
1 . No pneumothorax . 2 . Linear opacity in the right lung base , most likely atelectasis and left pleural effusion , unchanged .