Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Allowing for low lung volumes , the cardiac , mediastinal and hilar contours appear unchanged . Patchy left basilar opacity is most suggestive of minor atelectasis . There is a lenticular opacity projecting over the left lower posterior hemithorax , which is probably associated with the left posterior hemithorax and although not specific , its shape is suggestive of a new loculated pleural effusion . Other etiologies such as pneumonia or pulmonary mass are not excluded by this study , however , and investigation with chest CT should be considered when clinically appropriate .
    OUTPUT:
    
Left posterior opacity , smooth and lenticular , suggesting there may be a loculated effusion , although other etiologies including a pulmonary mass can not be excluded . Assessment with chest CT is suggested when clinically appropriate .