Sacral neuromodulation

A thin wire placed next to a nerve at the base of the spine sends mild electrical pulses that help the bladder and brain communicate better. You try it first for a few days to two weeks, and you only get the small permanent battery if it helps.

Also called SNM, sacral nerve stimulation, SNS, InterStim, Axonics, bladder pacemaker, pacemaker for the bladder, sacral nerve stimulator

Where: Test: clinic procedure room or operating room. Permanent implant: outpatient surgery center or hospital operating room
Anesthesia: Local numbing, usually with light sedation (medicine through an IV that relaxes you but lets you answer questions)
Time in the room: Office test wire: about 30 minutes. Each operating room stage: about 30 to 60 minutes
Hospital stay: Same day
Going home with: No urine tubes. During the test you wear a small outside stimulator taped to your lower back.
Back to normal: A few days for most daily activities. Avoid heavy lifting and hard bending or twisting for about 4 to 6 weeks after a permanent wire is placed
Back to work: About 1 to 3 days for desk work, longer for physical jobs

See the steps

SacrumS3 openingSacral nerveSpinal cordBladder

Where it happens. The highlighted part is what this procedure treats.

Overview

The bladder and brain talk to each other through nerves that leave the spine at the sacrum, the flat, triangle-shaped bone at the base of your spine. When those signals get mixed up, the bladder may squeeze too often, or may not empty. Sacral neuromodulation places a thin wire next to one of these nerves, the third sacral nerve (S3), and sends gentle, steady pulses. Over time this helps the bladder, pelvic floor, and brain work together more normally.

It is done in two parts. First comes a test phase: a temporary wire is placed and connected to a small outside stimulator for about 3 to 14 days while you keep a bladder diary. If your main symptoms improve by at least half, you move to the second part: a small battery (the implantable pulse generator) is placed under the skin of the upper buttock and connected to a permanent wire. If the test does not help, the wire is removed and nothing is left behind.

Devices are made by more than one company, and InterStim and Axonics are the best-known names. Some batteries are rechargeable with a small charger held over the skin. Others do not need charging and are replaced in a short procedure when they run down.

It is used for overactive bladder, for urinary retention without a blockage, and for bowel leakage. It does not treat leaking with coughing, sneezing, or exercise (stress incontinence).

The parts of your body involved

Nerves that control the bladder, bowel, and pelvic floor muscles come out of the lower spinal cord and pass through small holes in the sacrum. The third sacral nerve (S3) carries many of the signals between the bladder and the brain. The wire for this treatment sits right next to S3, entering through the S3 hole from the back. The battery sits in a pocket under the skin of the upper buttock.

Sacrum
The flat, triangle-shaped bone at the base of the spine, above the tailbone. It has small holes on each side for nerves to pass through.
S3 nerve
The third sacral nerve. It helps control the bladder, the pelvic floor muscles, and the bowel. The wire sits beside it.
Spinal cord
Carries messages between the brain and the nerves of the bladder.
Bladder
The organ that stores urine and squeezes to empty it. Its nerve signals are what the treatment adjusts.
Lead
The thin, flexible wire with small contacts at its tip. Soft plastic tines (tiny barbs) hold the permanent lead in place.
Battery (pulse generator)
A small sealed device, roughly the size of a large coin to a small matchbox depending on the model, that sends the pulses.

Why it’s done

Your urologist may suggest sacral neuromodulation when overactive bladder or urinary retention has not improved enough with simpler treatments, or when medicines are not tolerated. The AUA and SUFU guidelines list it as an option for carefully chosen people with overactive bladder who understand what it involves.

Overactive bladder that persists
Urges, frequent trips, and urge leaks that continue despite lifestyle changes, pelvic floor exercises, and medicines.
Urinary retention without a blockage
Some people, often younger women, cannot empty the bladder even though nothing is blocking it. This treatment can help some of them urinate on their own again and reduce or stop catheter use.
Bowel leakage too
Many people with bladder symptoms also have bowel leakage. The same device is used for both and may help both.
Avoiding catheter risk
Unlike bladder Botox, this treatment does not cause trouble emptying the bladder.
A treatment you can test first
You find out whether it works for you before committing to a permanent implant.

Other options

Lifestyle changes and pelvic floor therapy
Bladder training, timed voiding, fluid and caffeine changes, and pelvic floor muscle therapy. Safe and often helpful alongside any other treatment.
Medicines
Beta-3 agonists such as mirabegron or vibegron, and antimuscarinic medicines, relax the bladder.
Bladder Botox injections
Office injections repeated about every 6 to 12 months. In a large trial comparing the two in women, Botox reduced leaks slightly more on average, but caused more urinary infections and sometimes a need for catheters. The stimulator sometimes needed another operation to adjust or remove it.
Percutaneous tibial nerve stimulation (PTNS)
A needle near the ankle stimulates a leg nerve that shares roots with the bladder nerves. Weekly office sessions, no implant.
Implanted tibial nerve stimulators
Small devices placed under the skin near the ankle have become available in recent years. Ask whether one could suit you.
Catheterization for retention
For urinary retention, draining the bladder with a thin catheter several times a day is safe and effective, and is the usual alternative.

In the operating room, step by step

Press play or pick a step. Each drawing shows what your surgeon is doing at that moment. Your team may do some steps differently.

YouX-ray machineSurgeon

1 / 9

1. Lying face down

You lie on your stomach on padded pillows that tilt your hips up. You get light sedation so you are relaxed but can still tell the team what you feel. An X-ray machine (fluoroscopy) helps the doctor see the sacrum.

You lie on your stomach on padded pillows that tilt your hips up. You get light sedation so you are relaxed but can still tell the team what you feel. An X-ray machine (fluoroscopy) helps the doctor see the sacrum.
Using X-ray pictures, the doctor finds the S3 hole in the sacrum. The skin is numbed, and a thin hollow needle is passed through the skin into the hole.
A small current is sent through the needle. At the right spot, the muscles between your legs tighten and your big toe curls down. You may feel tapping or pulling in the vagina, scrotum, rectum, or the area between. Tell the team where you feel it.
More detail
The surgeon looks for a 'bellows' tightening of the pelvic floor and flexing of the big toe at low current. These responses, plus where you feel the sensation, confirm the S3 nerve.
A wire is passed through the needle and the needle is removed. In an office test, a thin temporary wire is taped to your back and pulled out at the end of the test. In a two-stage test, a permanent tined lead is placed in the operating room and connected to a temporary cable that comes out through the skin.
More detail
The tined lead has four contacts and soft barbs that anchor it in the tissue, so it moves less than a temporary wire. Many surgeons prefer it because more people get a clear answer from the test.
The wire is connected to a small outside stimulator taped to your back. You go home the same day and live normally, with care. You keep a bladder diary for about 3 to 7 days with an office wire, or up to about 2 weeks with a tined lead.
You and your doctor compare your diary with your baseline. A good test is usually at least a 50 percent improvement in your main symptoms. If it passes, you schedule the permanent implant. If not, the temporary wire is pulled out in the office, or the tined lead is removed in a short procedure.
More detail
For retention, success usually means a large drop in the amount you need to drain by catheter. Before calling a test a failure, the team often tries different settings, because programming changes can rescue some tests.
If you had an office test, the permanent tined lead is now placed in the operating room using the same steps: lying face down, X-ray guidance, and nerve testing. If you had a two-stage test, your permanent lead is already in place.
Through a cut about 1 to 2 inches long in the upper buttock, below the belt line, the surgeon makes a pocket under the skin. The lead is passed under the skin to the pocket and connected to the battery. The skin is closed with dissolving stitches and glue.
The device is programmed before you leave or at your first visit. You get a hand-held remote to raise or lower the strength, switch between programs, check the battery, and turn it off when needed.

After the operation

Right afterward

Short recovery
You rest for about 30 to 60 minutes while the sedation wears off.
Checking the settings
A nurse or device specialist checks that you feel the stimulation in the right place and that it is comfortable.
Dressing and remote
You are shown how to protect the dressing and how to use the remote or outside stimulator.
Device card
You receive an identification card for your device. Carry it with you.
Going home
Someone needs to drive you home after sedation.

At home

Pain
Soreness at the battery site and over the sacrum is normal for 1 to 2 weeks. Acetaminophen and ice packs (20 minutes at a time, with a cloth over the skin) usually help. Some people need a few days of stronger pain medicine.
During the test
Keep the dressing dry: no showers or baths over it. Sponge bathe instead. Keep the cable taped down and avoid bending, lifting, and hard exercise so the wire stays in place.
Wound care after the implant
Most teams let you shower after 1 to 3 days. Avoid baths, hot tubs, and swimming until the incisions are fully healed, usually about 2 weeks.
Activity
Walk every day. For about 4 to 6 weeks after a permanent lead, avoid heavy lifting, hard bending and twisting, and high-impact exercise, so scar tissue can anchor the lead.
Sitting
Sitting on the battery side can be tender at first. A soft cushion helps.
Driving
You can usually drive once you are off sedating pain medicine and can sit and turn comfortably, often within a few days.
Using the remote
If the feeling changes or symptoms return, try the remote first: check the battery, then adjust the level or program as you were shown. Call the team if this does not help.
Charging
If your battery is rechargeable, charge it as directed with the small pad held over the skin. If it is not, the battery is replaced when it runs low.
Medical care and tests
Tell every doctor, dentist, and imaging center that you have a sacral nerve stimulator. Do not have diathermy (a deep-heat treatment used by some therapists). MRI is possible with most current devices under specific conditions, so the imaging team must check your device first.
Sex and work
Sex is fine once you are comfortable. Some people turn the device down or off during sex. Most return to desk work in a few days.

Recovery timeline

Day 0
Test wire placed
You go home the same day with the outside stimulator.
Days 1 to 14
The test period
You live with the stimulator on and keep a daily diary, for about 3 to 7 days with an office wire or up to about 2 weeks with a tined lead.
End of the test
The decision
If symptoms improved by about half or more, you plan the implant. If not, the wire is removed.
Within a few weeks
The permanent implant
A short outpatient operation places the battery, and the permanent lead if you did not have one already.
Weeks 1 to 2 after the implant
Healing
Soreness at the battery site fades. Your incisions are checked.
Weeks 4 to 6
Back to full activity
Most people return to exercise and lifting.
Months 1 to 6
Fine-tuning
Settings are adjusted as needed. Another diary shows how much has changed.
Years
Living with the device
Regular check-ins. A non-rechargeable battery is replaced in a short procedure when it runs low, often after several years. Rechargeable batteries are designed to last much longer.

What it feels like

People often describe the treatment as stranger than it is painful. The sedation keeps you comfortable but awake enough to say where you feel the tapping. The test week takes patience: a cable taped to your back, no showers, and a diary to fill in.

Lying face down during the test
Drowsy and relaxed, then suddenly aware of odd tapping or pulling deep in the pelvis or a toe moving on its own. It can feel strange to be asked questions while sedated.
What helpsAnswer as simply as you can: front or back, left or right, comfortable or not. There are no wrong answers.
Feeling the stimulation for the first time
A light tapping, buzzing, or pulling in the vagina, scrotum, rectum, or the area between. It should never be painful.
What helpsIf it is too strong or in the wrong place, turn it down with the remote and call the team. Settings can be changed.
Living with the test wire
Careful with every move, worried about pulling the wire out, and tired of sponge baths.
What helpsKeep the cable taped flat, wear loose clothes, and sleep on your side or back with care. It is only for days.
Looking at the diary numbers
Relief if the numbers improve; disappointment if they do not.
What helpsTalk with the team before deciding. A change in settings sometimes turns a poor test into a good one.
After the battery goes in
A sore buttock and trouble sitting comfortably for a week or two.
What helpsIce packs, a cushion, and short walks. The soreness fades steadily.
Months later
Many people forget the device is there. Some notice the stimulation more when they change position, for example sitting compared with standing.
What helpsAsk about a second program for different positions, or a small change in the level.
If symptoms creep back
Worry that it has stopped working.
What helpsCheck the battery and the remote first. Reprogramming often restores the benefit before anything else is needed.

How well it works

Success is measured with your bladder diary. A good result is at least half as many leaks or bathroom trips, or, for retention, being able to urinate with much less or no catheter use. In a large five-year study of people with overactive bladder who had the implant, most still had at least a 50 percent improvement at five years.

Bladder diary
Repeated at follow-up visits to compare with your starting point.
Programming visits
Settings are adjusted to keep the best balance of comfort and benefit.
Battery checks
The remote shows battery status. Your team plans a replacement before a non-rechargeable battery runs out.
For retention
Leftover urine is measured with a bladder scan or catheter volumes to see how well you now empty.
Bowel symptoms
If you also had bowel leakage, your team will ask about it, since it often improves as well.

Risks

Every operation has risks. These are the ones people ask about most, with honest odds where good numbers exist. Your surgeon’s own results matter more than averages.

Common

The test does not help enough

Not everyone responds. If the test fails, the wire is removed and you have lost only some time.

Pain or tenderness at the battery or wire site

Usually mild and fades over weeks. Occasionally the battery needs to be moved to a more comfortable spot.

Unwanted or uncomfortable stimulation

A jolting feeling, or stimulation felt in the leg, foot, or the wrong area. Usually fixed by reprogramming.

Benefit fading over time

Some people lose part of the benefit over months or years. Reprogramming often helps; sometimes the lead needs to be repositioned.

Another procedure later

Over the years, a fair number of people need another operation to adjust, replace, or remove part of the system. Battery replacement for non-rechargeable devices is expected.

Less common

InfectionA few in 100 people

Redness, swelling, or drainage at the battery or wire site. An infected device usually has to be removed, and can be replaced later once the infection has cleared.

Lead moving out of place

The wire can shift, especially early on, and the benefit may drop. It may need to be repositioned.

Changes in bowel habits

Some people notice looser or firmer stools. This usually settles or improves with programming.

Bruising or a collection of blood at the battery site

Usually goes away on its own; occasionally it needs to be drained.

Rare

Nerve irritation or lasting leg pain

Rare, and usually improves when the settings are changed or the lead is moved.

Device problems

A broken wire or a battery fault that needs replacement.

Skin wearing thin over the battery

More likely in very thin people. It may need a revision of the pocket.

Call your care team or go to the emergency room if

Fever of 101°F (38.3°C) or higher
Redness, warmth, swelling, or pus at the battery or wire site, or an incision that opens
A painful, quickly growing swelling at the battery site
A jolting or shock-like feeling that does not stop when you turn the device off
New weakness or numbness in a leg or foot
During the test: the cable pulls loose or the wire comes partly out (do not push it back in)
You cannot urinate at all and your bladder feels full

Questions to ask your surgeon

Do you recommend the office test wire or the two-stage method for me, and why?
Which device would you use, and is it rechargeable?
How long does the battery usually last, and how is it replaced?
Will I be able to have MRI scans with this device, and of which parts of the body?
What will count as a successful test for my symptoms?
What should I avoid during the test and after the implant?
Who programs the device, and how do I reach them if it stops helping?
How many of these implants do you do each year?
What should I do with the device if I become pregnant?
If the test does not work, what are my next options?

Words you may hear

Sacral neuromodulation: Treatment that uses mild electrical pulses on the sacral nerves to change how the bladder and bowel nerves signal.
Sacrum: The triangle-shaped bone at the base of the spine.
S3 nerve: The third sacral nerve, which carries signals for the bladder, bowel, and pelvic floor.
Lead: The thin wire that carries the pulses to the nerve.
Tines: Small soft barbs on the permanent lead that hold it in place.
Implantable pulse generator (IPG): The small battery device placed under the skin of the buttock.
Percutaneous nerve evaluation (PNE): An office test using a thin temporary wire for a few days.
Staged implant: A two-step approach: a permanent lead and test first, then the battery if the test works.
Fluoroscopy: Live X-ray pictures used to guide the needle into the right hole in the sacrum.
MRI conditional: A device that is safe in an MRI scanner only when specific conditions set by the maker are followed.
Diathermy: A deep-heat treatment used by some therapists and dentists. It must not be used on people with this device.
Non-obstructive urinary retention: Being unable to empty the bladder when nothing is physically blocking the flow.
Bladder diary: A record of your trips to the bathroom, urges, leaks, and catheter volumes.

Common questions

Will it shock me?

No. The pulses are mild. Most people feel a light tapping or pulling in the pelvis, and many stop noticing it over time. If it ever feels sharp or jolting, turn it down or off and call your team.

Can I have an MRI?

Most current devices allow MRI under specific conditions set by the maker, and some allow scans of the whole body. Always tell the imaging center you have the device. They will check its model and settings, and you may need to turn it off before the scan.

Can I go through airport security?

Yes. Show your device card. Metal detectors may detect the device, and security staff can check you another way.

What if the test does not work?

The wire is removed and nothing is left in your body. You can move on to other options such as bladder Botox.

Can it be removed later?

Yes. The battery and lead can be removed in a short procedure if you no longer want or need them.

How often do I need to charge it?

That depends on the model and your settings. Rechargeable models are charged with a small pad held over the skin, typically every week to every few weeks. Non-rechargeable models need no charging but are replaced when the battery runs low.

Will it also help bowel leakage?

It often does. Sacral neuromodulation is also approved for fecal incontinence.

Sources this page draws on

American Urological Association / SUFU, The AUA/SUFU Guideline on the Diagnosis and Treatment of Idiopathic Overactive Bladder (2024)
Journal of Urology (Siegel and colleagues), Five-year followup results of a prospective, multicenter study of patients with overactive bladder treated with sacral neuromodulation (InSite study) (2018)
JAMA (Amundsen and colleagues), Effect of intradetrusor onabotulinumtoxinA vs sacral neuromodulation on urgency urinary incontinence among women (ROSETTA trial) (2016)
Urology Care Foundation, Overactive Bladder (OAB)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Nerve Disease and Bladder Control

Written November 2026. This page explains what usually happens. It is not medical advice and does not replace a conversation with your own surgeon, whose plan for you comes first.

Sacral neuromodulation

Overview

The parts of your body involved

Why it’s done

Other options

Getting ready

Weeks before

The week before

The day before and the morning of

In the operating room, step by step

1. Lying face down

After the operation

Right afterward

At home

Recovery timeline

What it feels like

Lying face down during the test

Feeling the stimulation for the first time

Living with the test wire

Looking at the diary numbers

After the battery goes in

Months later

If symptoms creep back