Sacral Neuromodulation

Overview

Here is how it works: a small wire (called an electrode) is placed near the sacral nerves (S3) at the base of your spine — the nerves responsible for telling your bowel when to hold and when to release. That wire connects to a tiny pulse generator (the device itself) implanted just under the skin of your buttock. Together they send gentle, continuous electrical signals that help your brain and bowel communicate better.

The good news is that before you commit to anything permanent, you get to try it first. The procedure is done in two stages — a trial phase lasting 2–4 weeks where you wear an external device and see how much it helps, followed by permanent implantation only if the trial shows meaningful improvement (generally more than a 50% reduction in leakage episodes). If the trial does not help, the wire is simply removed.

Who needs this procedure?

• You have faecal incontinence (leakage of stool) that has not improved with diet changes, medications, or pelvic floor physiotherapy
• Your sphincter muscle is intact or has already been repaired — SNM can help even if there is a small remaining gap in the muscle
• You experience urge incontinence — where you feel the urge and cannot make it to the toilet in time — which responds especially well
• You have passive incontinence — where leakage happens without you realising
• A previous sphincter repair has not given you the improvement you hoped for
• You prefer not to have, or are not suitable for, sphincteroplasty (sphincter repair surgery)

Benefits

• Very effective — around 70–80% of patients see more than a 50% drop in leakage episodes
• Completely reversible — the device can be adjusted, turned off, or removed at any time
• Helps with both urge and passive incontinence
• Avoids the longer recovery of open sphincter repair surgery
• Benefits last — most people maintain improvement for more than 5 years
• If you also have urinary urgency or leakage, SNM can help with that too

Risks & considerations

• Infection at the implant site — happens in about 3–5% of patients and is usually treatable with antibiotics, though the device may occasionally need to be removed temporarily
• Lead migration — the wire can shift position in 5–10% of cases, sometimes needing a small procedure to reposition it
• Battery runs flat after 5–10 years — a straightforward procedure replaces just the pulse generator (the battery part), not the lead
• Discomfort at the implant site — affects about 5–10% of people, often settles on its own or with device adjustment
• Device malfunction — uncommon; easily identified at follow-up checks
• MRI scans — modern devices are MRI-compatible in many settings, but you will need to tell any imaging centre that you have an implant so they can check compatibility first

Before the procedure

• Before the trial, you will have anorectal manometry (a short pressure test) and an endoanal ultrasound (an internal scan of the sphincter muscles) — these are painless tests done in the rooms and give Mr Nguyen a clear picture of how your bowel is working before treatment
• You will be asked to keep a bowel diary for a few weeks before the trial — this helps measure how much improvement the device actually makes
• You will be prescribed antibiotics to take around the time of the procedure
• Mr Nguyen will explain both stages of the procedure fully and answer any questions you have before you consent

On the day

• Stage 1 — the trial: This is a day procedure done under local anaesthetic with light sedation so you are relaxed and comfortable. A thin wire is placed near the sacral nerve (S3) in your lower back using X-ray guidance, and connected to a small external device you wear on your belt or in a pocket. You go home the same day.
• You use the trial device for 2–4 weeks at home and keep a diary of your symptoms. If you see a clear improvement, you move on to Stage 2.
• Stage 2 — the permanent implant (if the trial works): Done under general anaesthetic. The permanent electrode is secured in place and the pulse generator is implanted just under the skin of your buttock through a small incision. It sits flush under the skin — you can feel it but it is not visible through clothing.
• The device is switched on and programmed to your comfort level before you leave
• Most patients go home the same day or stay one night

Recovery & aftercare

• During the trial (weeks 1–4): You can go about your normal life. You will manage the external device yourself at home — it is straightforward to use and the team will show you how
• If the trial does not help enough: the wire is removed as a simple outpatient procedure and no permanent implant is placed
• After permanent implantation: Keep activity light for the first 2 weeks and avoid bending deeply or twisting at the waist while the wound heals
• By week 4: You can return to your normal activities including exercise
• The device settings are fine-tuned at follow-up appointments — small adjustments can make a big difference to how well it works
• Long-term: you will have an annual check-up and, when the battery eventually runs low (usually after 5–10 years), a simple procedure replaces just the generator
• You will be given a device ID card to carry — show it at airports and tell any doctor or radiologist about your implant before scans
• A post-operative review with Mr Nguyen is routinely arranged 2–6 weeks following your procedure, with timing depending on the type of operation — this review is provided at no charge

Related patient guides

Articles written for patients and their families — to help you understand what you are experiencing and what to expect.