Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided pneumothorax is seen , small to moderate in size . Surgical chain sutures seen at the left hilum and left lung apex . The lungs are otherwise clear . The lower trachea and mediastinum are slightly shifted to the right . Cardiomediastinal silhouette is otherwise within normal limits . No acute osseous abnormalities .
    OUTPUT:
    
Small to moderate left - sided pneumothorax . Mild rightward mediastinal shift .