Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post coronary artery bypass graft surgery . Left - sided cardiac and hilar borders are obscured , but otherwise cardiac , mediastinal borders are visualized and appear unchanged . The right lung remains clear without pleural effusion . On the left , the lower half of the hemithorax is opacified with a large pleural effusion and probably extensive atelectasis , noting no net shift in mediastinal structures . Projecting over the lateral left lung apex , a small new vague area of nodularity measuring up to about 10 mm is noted either within the lung parenchyma or perhaps associated with subpleural thickening or sclerosis in the left second rib , but new since the prior study .
    OUTPUT:
    
Large pleural effusion with the suspected atelectasis . Small nodular opacity in the left upper lung of unclear etiology . Investigation with CT , preferably with intravenous contrast is suggested when clinically appropriate .