Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright portable view of the chest demonstrates low lung volumes . Left pleural effusion is noted . Retrocardiac opacity likely represents atelectasis . The right lung is clear without pleural effusion or pneumothorax . Hilar and mediastinal silhouettes are unremarkable . Heart size is top normal . There is no pulmonary edema .
    OUTPUT:
    
Left lung base opacity , likely atelectasis with associated small left pleural effusion .