Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the last exam , in a large left lower lobe opacity has developed , likely a large pleural effusion , causing mass effect on the mediastinum and the left hemidiaphragm . The remaining left upper lung and the right lung are clear . The cardiomediastinal silhouette is difficult to evaluate , though likely unchanged .
    OUTPUT:
    
Interval development of large left lower lobe opacity , likely a large pleural effusion . Further evaluation with CT is recommended given the extent and mass effect on the adjacent structures .