Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable view of the chest . The large left pleural effusion persists , not definitely changed since most recent exam given differences in positioning . The right lung remains clear . There is no visualized pneumothorax on either side . No acute osseous abnormality detected .
    OUTPUT:
    
Persistent large left pleural effusion . No visualized pneumothorax .