Sacral nerve stimulation is used to treat patients with more severe forms of faecal incontinence. Nerves that send and receive electrical signals from the pelvic floor muscles, the anal sphincter and the rectum enter and exit the spinal column through the sacrum (the flat bone at the base of the spine). By positioning an electrical lead in contact with these nerves, a constant low voltage stimulus can be delivered to this area. A temporary electrode is inserted through the sacrum under anaesthesia and left in place for 2-3 weeks. During this period, a diary of bowel function and continence is maintained. If there is a significant improvement in continence with the stimulation, a permanent stimulator can be placed with a "pacemaker" in the buttock.