Sacral Nerve Stimulation (SNS)


Sacral Nerve Stimulation (SNS) is primarily a treatment for faecal incontinence. It involves low-level electrical stimulation to the sacral nerve supply of the lower bowel and sphincters, delivered by an implantable device similar to a cardiac pacemaker. The device is placed within the fatty tissue of the buttock and is controllable by an external handset. This allows the user to adjust or turn off the device.

The exact means by which SNS works is still being investigated. It does not increase muscle tone or cause spasms, but we do know that it improves blood flow and “alertness” of nerves in the bowel. It is also thought to improve communication and coordination between the bowel and the brain.


We will need to see you in clinic to assess your symptoms and to perform an examination.

Most patients having this operation will need an endoscopic (telescope) test on the bowel (colonoscopy or flexible sigmoidoscopy). We will also perform studies on the anal sphincter to look at its structure and function (anorectal physiology and ultrasound) and transit studies and a proctogram. These tests will look for damage to the sphincter muscle whilst ruling out other causes for your symptoms such as prolapse or inflammation.

If these investigations identify any important conditions, we might recommend treatment of these before considering sacral nerve stimulation.

Some patients, despite appearing suitable on the basis of these investigations, do not benefit from the procedure. A “test” or “temporary” wire is therefore inserted in patients before the permanent implant is undertaken.


Patients who are considered likely to benefit from sacral nerve stimulation are first given a temporary or test wire. This is usually done as an outpatient procedure, in a treatment room. You usually remain awake throughout the procedure.

You will be asked to lie on a bed. You will be given an injection to numb the skin over the lower spine just above the buttocks. Then, a very fine wire will be inserted under your skin. The other end of the wire is attached to a little stimulator (battery box) like an ipod, worn on a belt.

It usually takes about 30 minutes to insert the temporary wire. You will be able to drive and return to work later the same day if you wish.


The test period usually lasts two to three weeks.

The wire and stimulator connectors are completely covered up with dressings. It is this dressing that holds the wire in place, so it is very important not to remove or dislodge it during the test period. You will be given extra dressings to put on top if the edges begin to peel. You should not bathe or shower during the test period as it is important that the dressings, the wire and stimulator stay dry and do not get dislodged. You will be shown how to disconnect the wire from the stimulator and we would recommend that you do this when driving. Avoid excessive bending, heavy lifting, strenuous exercise and sexual intercourse.

You will be given a diary to fill in so that your surgeon can assess how beneficial the temporary stimulator has been. About three quarters of patients improve with the temporary wire and are then offered a permanent implant.

At the end of the test period the temporary wire is removed at a clinic appointment. Removal of the wire is straightforward and does not even require a local anaesthetic.


This is a very safe procedure. No major complications have been reported in over 175,000 patients. Sometimes a small bruise occurs at the wire insertion point. It is possible that an infection could occur at the insertion site, or you could have an allergic reaction to the dressings. Even if the test fails, no deterioration of bowel function has ever been reported.


The permanent stimulator may to be inserted under a local or a general anaesthetic.

A wire is inserted into the buttock in the same location as the test wire. The other end of the wire is tunnelled under the skin and attached to a small stimulator buried in the fat of the buttock. The stimulator is the size of a small matchbox. At the end of this procedure there are no wires or stimulators visible from the outside. You will usually be allowed home from hospital on the same day.

Sometimes it is possible to turn the stimulator on immediately, but you may need to come back to clinic a week or so later to have the implant switched on.


The hospital will contact you before your operation to arrange for you to come in for a pre-assessment visit. This normally lasts 30-60 minutes.

At your visit you will have some basic health checks to ensure you are fit for surgery. These may include:

  • Blood Pressure
  • Pulse
  • Weight
  • Urine Analysis
  • Electrocardiogram (ECG)
  • Medical History Questionaire
  • MRSA Screen

The nurse will advise whether you should continue to take any regular medication.

You will also be given instructions about when to stop eating and drinking before your operation, what to bring into hospital with you and when to arrive.


You will be given full instructions before you are discharged home and contact details in case you have any questions. You will be supplied with a wireless handset that communicates with the implanted stimulator, enabling you to turn it on and off and change the settings. It is not necessary to turn off the stimulator in order to pass a bowel movement, and you should not often need to make changes to the settings.

When the wounds have healed, you can shower and bathe as usual. You can drive as normal.

Even if your implant was activated on the day of the operation, you will normally need at least one further clinic visit to get the settings right. The correct settings are different for everybody, so it may take a number of visits to get it exactly right for you.

We will keep you under regular review to ensure that you are continuing to benefit from the stimulator. Once up and running, you will normally need a minimum of one visit a year to check the implant is working correctly and that the settings are still correct.


SNS is a relatively safe procedure. Bleeding or bruising at the implant site is possible though very uncommon. Occasionally (less than 2%) patients experience infection of the wire or pacemaker.

In 5% of patients, the permanent wire will not work even though the temporary wire did. Very occasionally this can be corrected at a second operation by repositioning the wire. In other patients this can be due to placebo effect, where the patient experiences a perceived or actual improvement in symptoms with the temporary wire which is not due to the physical effects of the SNS.

5-10% of people experience pain after the operation. Pain caused by the wire is felt in the leg. Implantation under local anaesthetic, where patients give feedback during the operation, helps to minimise this. Pain generated by the box itself can be over the scar or deep in the buttock. This may be triggered by excessive weight loss or a fall that moves the box out of position.


If you get back pain, you should try turning off the stimulator for a couple of days. If the pain persists, then it is not due to the stimulator and you should consult your GP. If the pain stops, then you need to contact us for an appointment and we will make adjustments to the stimulator.

Pain in your buttock in the area where the device is implanted could be caused by the implant. If you see redness around the scar, or feel the device moving or tilting when you move, contact us for an appointment.

Leg pain caused by SNS can only be felt on the side that the wire and box are implanted. If you have pain in your other leg, contact your GP. If you have pain in the leg on the implant side (especially below the knee), try switching off the stimulator for a couple of days and see if this stops the problem. Leg pains are more likely than back pains to be related to the stimulator, so don’t worry if this happens. Make an appointment to come into clinic and we can make adjustments that should be able to overcome this.


Once you have healed after your operation, you should be able to go about life as normal. After four weeks you may resume all normal activities.

However, because you have a metal implant:

  • You cannot go through airport scanners without setting off the alarm. You will be given a small card to carry to explain your situation to the necessary authorities, or you may ask your surgeon for a letter if you intend to fly. The SNS implant is unlikely to set off security alarms in shops.
  • You will not be able to have an MRI scan, other than of your brain.


The life of the battery is normally 5-8 years. After this time, the main part of the implant (but not the wires) needs to be replaced. This is a similar but smaller operation to having the whole implant put in, and can be done under local anaesthetic. This is often referred to as a ‘battery change’, but this can be confusing as it is actually a replacement of the whole main part.

Please be advised that the information on this website is not a substitute for professional medical advice, diagnosis or treatment