Urodynamic testing

Urodynamic testing measures how your bladder fills, stores and empties. Thin catheters in the bladder and rectum record pressures while the bladder is slowly filled with water and then while you urinate.

Also called UDS, urodynamics, urodynamic study, multichannel urodynamics, cystometry, cystometrogram, CMG, pressure-flow study

Where: Clinic urodynamics room
Anesthesia: None; you stay awake so you can describe what you feel
Time in the room: 30 to 60 minutes of testing; about 1 to 1.5 hours in the office
Hospital stay: Go home right after
Back to normal: The same day; mild burning may last a day or two
Back to work: The same day or the next day

See the steps

BladderUrethraBladder neckRectum

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

Overview

Urodynamic testing, often called urodynamics or UDS, is a set of tests that measures how your bladder and urethra (the tube that carries urine out) store and release urine. It shows what is happening inside the bladder while it fills and while you urinate, which symptoms alone cannot always tell.

Thin, soft catheters (tubes) are placed in your bladder through the urethra and in your rectum (back passage). Each carries a pressure sensor. Your bladder is slowly filled with sterile water while a computer records the pressures and you tell the team what you feel. You are asked to cough and strain to check for leaks. At the end, you urinate with the bladder catheter still in place so pressure and flow can be measured together.

The test is done while you are awake, without anesthesia. Leaking during the test is expected and helpful, because it shows the team exactly what happens. The results guide treatment for leakage, overactive bladder, trouble emptying, and bladder problems caused by nerve conditions.

Not everyone with bladder symptoms needs urodynamics. AUA and SUFU guidelines say, for example, that women with straightforward stress leakage can often go ahead with treatment without it. The test is most useful when the picture is unclear, symptoms are mixed, an earlier treatment has not worked, a nerve condition is present, or surgery is being planned.

The parts of your body involved

The bladder is a muscular bag. Its wall, the detrusor muscle, stays relaxed while the bladder fills and squeezes when you urinate. As it fills, nerves send messages to the brain about how full it is. The urethra is held closed by the sphincter muscles and the pelvic floor, which relax when you choose to urinate. In men, the prostate surrounds the urethra just below the bladder and can narrow it. Urodynamics measures pressure inside the bladder and pressure inside the belly, using the rectum. The difference between the two shows how hard the bladder muscle itself is squeezing.

Bladder and detrusor muscle
Stores urine at low pressure, then squeezes to empty. Urodynamics checks how it fills, how it feels, and how it squeezes.
Bladder neck and urethra
The outlet and the tube to the outside. A leak with coughing means this outlet is not closing firmly enough.
Sphincter and pelvic floor
Muscles that keep the urethra closed and relax to let urine out. Sticky sensors near the anus can record their activity.
Prostate
In men, a gland around the urethra below the bladder. When enlarged, it can block flow, which the pressure-flow study can show.
Rectum
A small balloon catheter here measures pressure in the belly, so the computer can separate belly pressure from bladder muscle pressure.

Why it’s done

Urodynamics is offered when knowing exactly how your bladder behaves is likely to change your treatment.

Leakage that is unclear or mixed
When it is hard to tell whether leakage comes from a weak outlet (stress leakage), an overactive bladder muscle (urge leakage), or both.
Before surgery
Before some operations for leakage, prolapse or an enlarged prostate, especially if you have had surgery before or symptoms are mixed.
Overactive bladder that has not improved
When medicines and bladder training have not helped and more advanced treatments are being considered.
Trouble emptying
A slow stream or urine left behind can come from a blockage or from a weak bladder muscle. The pressure-flow study tells these apart, which changes treatment.
Nerve conditions
Spinal cord injury, multiple sclerosis, spina bifida and similar conditions can cause high pressure in the bladder that silently harms the kidneys. Urodynamics checks for it and guides treatment.
Problems after a previous operation
New leakage or trouble emptying after prostate, bladder or sling surgery.

Other options

Bladder diary, exam and simple tests
For many people, a 2 to 3 day bladder diary, a urine test, a physical exam and a quick ultrasound bladder scan are enough to start treatment.
Flow test and bladder scan alone
A flow test and a bladder scan for leftover urine need no catheters. They show how well you empty but not why.
Trying treatment first
Starting pelvic floor exercises, bladder training or medicines, and doing urodynamics only if they do not help.
Cystoscopy
A look inside the bladder with a camera. It shows the structure of the bladder and urethra, not how they work, and is sometimes done along with urodynamics.
Going straight to surgery for simple stress leakage
For women with uncomplicated stress leakage confirmed on exam, a large trial found that skipping urodynamics before sling surgery did not worsen results.

The procedure, 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.

YouScrub nurse

1 / 10

1. The flow test

You sit on a special commode chair, in private, and urinate as you normally would. It looks like an ordinary toilet seat, but the funnel below measures how fast and how much you urinate.

You sit on a special commode chair, in private, and urinate as you normally would. It looks like an ordinary toilet seat, but the funnel below measures how fast and how much you urinate.
The machine draws a curve of your flow over time. A strong, smooth, bell-shaped curve is normal. A slow, flat or stop-start curve suggests a blockage or a weak bladder muscle.
More detail
This test, called uroflowmetry, is most reliable when you pass a reasonable volume. If you could not hold much, the team may repeat it.
Right after you urinate, a quick ultrasound scan over your lower belly, or the first catheter, measures how much urine is left in your bladder.
You lie or sit on the test chair. After cleaning and, often, numbing gel, a very thin catheter is passed through the urethra into the bladder. A second small catheter with a soft balloon is placed just inside the rectum. Both are taped in place.
More detail
The bladder catheter is much thinner than a usual catheter and has two channels: one to fill the bladder, one to measure pressure. Small sticky pads near the anus may also be placed to record the pelvic floor muscles, a measurement called EMG.
Sterile water at room temperature flows slowly into your bladder, usually over about 10 to 20 minutes. You tell the team when you first feel the bladder filling, when you first want to urinate, when the urge becomes strong, and when you feel you cannot hold any more.
During filling, a healthy bladder muscle stays relaxed and the pressure stays low. The computer shows whether the muscle squeezes on its own before you choose to urinate, which is a sign of overactive bladder, and whether pressure rises too steeply as the bladder fills.
More detail
Squeezes you did not choose are called detrusor overactivity. A bladder that becomes stiff and high-pressure as it fills has low compliance, which matters most in people with nerve conditions because it can harm the kidneys.
With the bladder partly full, you are asked to cough and bear down, sometimes standing. The team watches for leaking and records the pressure at which it happens. If you have prolapse, it may be gently supported to see whether leakage is hidden behind it.
When your bladder feels full, you are asked to urinate into the commode with the thin bladder catheter still in place. Measuring pressure and flow together shows whether a slow stream is caused by a blockage or by a weak bladder muscle.
More detail
This is called a pressure-flow study. High bladder pressure with a slow flow points to a blockage, such as an enlarged prostate. Low pressure with a slow flow points to an underactive bladder.
In some people, the bladder is filled with contrast dye instead of water, and X-ray pictures are taken during filling and urinating. This shows the shape of the bladder, whether urine flows back up to the kidneys, and exactly where a blockage sits.
The catheters slide out easily, and any leftover water is drained or urinated out. You can clean up, dress, and go home.

After the procedure

Right afterward

Cleaning up
Wipes, pads and a spare pair of underwear make it easy to clean up and dress in private.
Your results
Some findings are clear right away. Often the full tracing is reviewed afterward and discussed with you at a follow-up visit.
The first time you urinate
It may burn or look slightly pink.
Heading home
You can usually drive yourself home and return to your day.

At home

Burning
Mild burning when you urinate is common for a day or two.
Pink urine
A little blood in the urine can happen for a day.
Drink extra
Drink a few extra glasses of water for the rest of the day, unless you have been told to limit fluids.
Medicines
Restart any bladder or prostate medicines you stopped, unless your team tells you otherwise.
Activity, work and sex
Return to normal activity, work and sex whenever you feel comfortable, usually the same or the next day.
Watch for infection
Burning that gets worse after 2 days, fever, or cloudy, foul-smelling urine can mean infection. Call your team.
If you have a spinal cord injury
Watch for a pounding headache, flushing or sweating above your injury level, or a stuffy nose over the rest of the day. These can be signs of autonomic dysreflexia and need urgent action.
Your follow-up visit
Your urologist will explain the results alongside your symptoms and diary, and suggest treatment.

Recovery timeline

Days before
Bladder diary
Two to three days of tracking drinks, urination and leaks.
Minute 0
Flow test
Urinating in private into a measuring commode, then a quick bladder scan.
Minutes 10 to 20
Catheters placed
A brief sting and pressure as the thin catheters go in.
Minutes 20 to 50
Filling and testing
Slow filling, telling the team what you feel, coughing and straining, then urinating with the catheter in.
End of visit
Catheters out
Clean up, dress and go home.
That evening
Mild burning
Burning and frequent urges are common. Drink extra water.
Days 1 to 2
Back to normal
Any burning or pink urine settles.
1 to 3 weeks
Results and a plan
Your urologist goes over the results and recommends treatment.

What it feels like

Most people say urodynamics was less uncomfortable than they feared but more personal than they expected. Being asked to leak and urinate in front of others is often the hardest part, and the team understands that.

Before the test
Dread about embarrassment, about a catheter in the rectum, or about leaking in front of strangers.
What helpsRemember the team does this test many times a week, and leaking is exactly what they need to see. Ask any questions before you start.
The flow test
Pressure to perform. Urinating on command into a machine can make it hard to start.
What helpsTake your time. Running water or relaxing your breathing can help. If it does not work the first time, the team can try again later.
The catheters going in
A brief sting as the bladder catheter passes, then little sensation. The rectal catheter feels like mild pressure, as if you need a bowel movement.
What helpsBreathe out slowly and relax your pelvic floor as the catheter passes.
The filling
Cool water and a growing feeling of fullness, just like a real full bladder. Some people feel their bladder squeeze and leak, which can be embarrassing.
What helpsDescribe what you feel as honestly as you can. A leak is useful information, not a failure.
Coughing and straining
Self-consciousness about leaking in front of others, especially when asked to stand.
What helpsPads are in place. The team is watching numbers on a screen and is focused on the tracing.
Urinating with the catheter in
Many people find it hard to urinate with a catheter in and people nearby. Shy bladder is very common.
What helpsAsk for privacy. The team can step behind a screen or out of the room while the computer records.
Afterward
Relief that it is over, mild burning, and curiosity or worry about the results.
What helpsDrink extra water. Ask when you will hear the results and how they will guide treatment.

How well it works

The test produces a tracing of pressures, volumes and flow. Your urologist reads it together with your symptoms and bladder diary to explain what is happening and which treatment fits.

Flow and emptying
How fast and how completely you empty. A slow flow can come from a blockage or a weak bladder muscle, and the pressure-flow study tells which.
Bladder storage
How much your bladder holds, when you first feel the urge, and whether the pressure stays low as it fills. High filling pressure can harm the kidneys over time, especially with nerve conditions.
Overactive bladder squeezes
Squeezes during filling that you did not choose point toward overactive bladder and guide medicines, Botox or nerve stimulation.
Stress leakage
Leaking with a cough or strain, and the pressure at which it happens, confirms stress leakage and helps plan treatments such as slings.
Blockage or weak bladder
Shows whether surgery to open the outlet, such as prostate surgery, is likely to help, or whether catheter drainage may be needed.

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

Burning with urinationMany people

For a day or two.

Frequent urges

For the rest of the day.

Pink urine

A little blood for a day.

Less common

Urinary infection

Signs are worsening burning after 2 days, fever, or cloudy, foul-smelling urine. It is treated with antibiotics.

An incomplete test

Some people cannot urinate with the catheter in, or their usual leaks or squeezes do not happen during testing. The results may then be less complete.

Discomfort or anxiety

Some people find the catheters or the setting distressing. The team can pause at any time.

Rare

Autonomic dysreflexia

In people with a spinal cord injury at or above T6, a full bladder can trigger a sudden, dangerous rise in blood pressure. The team monitors blood pressure and drains the bladder at once if it happens.

Unable to urinate afterward

Short-term trouble urinating, more likely in men with a blocked outlet. A catheter may be needed briefly.

Injury to the urethra

Very rare with the thin catheters used.

Kidney infection

Fever with back or side pain. It needs prompt antibiotics.

Call your care team or go to the emergency room if

Fever of 101°F (38.3°C) or higher, or shaking chills
Burning that gets worse after 2 days or lasts more than 3 days
You cannot urinate, or your bladder feels full and painful
Bright red urine, clots, or bleeding that lasts beyond 2 days
Pain in your side or back
With a spinal cord injury: a pounding headache, flushing or sweating above the injury, or very high blood pressure (sit up, check your catheter or bladder, and call 911 if it does not settle quickly)

Questions to ask your surgeon

Why do I need urodynamics, and how will the results change my treatment?
Should I stop any bladder or prostate medicines beforehand, and for how long?
Should I arrive with a full bladder?
Where will the pressure catheters go?
Will you use X-ray pictures (video urodynamics)?
Will I get an antibiotic?
Who will be in the room during the test?
What happens if I cannot urinate with the catheter in?
When and how will I get my results?
Can I drive and go back to work afterward?

Words you may hear

Urodynamics: Tests that measure how the bladder and urethra store and release urine.
Uroflowmetry: Measuring how fast and how much you urinate, using a special commode.
Post-void residual: The amount of urine left in the bladder after you urinate.
Cystometry: Measuring bladder pressure and feeling while the bladder is filled. The tracing is called a cystometrogram.
Detrusor: The muscle in the bladder wall that squeezes to empty the bladder.
Detrusor overactivity: Squeezes of the bladder muscle during filling that you did not choose. A sign of overactive bladder.
Compliance: How easily the bladder stretches as it fills. Low compliance means pressure rises steeply.
Leak point pressure: The pressure at which urine leaks during coughing or straining.
Pressure-flow study: Measuring bladder pressure and urine flow at the same time while you urinate.
Bladder outlet obstruction: A blockage at the bladder outlet or urethra, such as from an enlarged prostate or scar tissue.
Underactive bladder: A bladder muscle that does not squeeze strongly or long enough to empty fully.
EMG: Electromyography: recording the electrical activity of the pelvic floor muscles with small sticky pads.
Video urodynamics: Urodynamics done with contrast dye and X-ray pictures to show the bladder's shape and movement.
Autonomic dysreflexia: A dangerous rise in blood pressure that can happen in people with high spinal cord injuries, often triggered by a full bladder.
Bladder diary: A record of what you drink, when and how much you urinate, and when you leak, kept for a few days.

Common questions

Will it hurt?

Most people feel a brief sting when the bladder catheter goes in, pressure from the rectal catheter, and the strong urge of a full bladder. No anesthesia is needed. Burning afterward usually settles within a day or two.

What if I leak during the test?

That is expected and useful. Pads and covers are in place, and the team sees it every day. A leak during the test often gives the exact answer needed to choose treatment.

What if I can't urinate in front of people?

This is very common. Ask for privacy, and the team can step away while the computer records. If you still cannot go, the rest of the test is still useful.

Do I need this before surgery for stress leakage?

Not always. For women with simple stress leakage confirmed on exam, a large trial found that skipping urodynamics before surgery did not change results, and AUA/SUFU guidelines allow going ahead without it. It is more helpful when symptoms are mixed, when you have had surgery before, or when you have trouble emptying.

Why is there a catheter in my rectum?

Pressure inside the belly pushes on the bladder whenever you cough, move or strain. The rectal catheter measures that belly pressure so the computer can subtract it and show how hard the bladder muscle itself is squeezing.

Should I stop my bladder medicines?

Ask your team. Some prefer you stop them for several days so the test shows your bladder without them. Others want to see how you do on them.

Can I eat and drive?

Yes. No fasting or sedation is needed. You can drive yourself and return to normal activities the same day.

How long until I get results?

Some findings are clear during the test. A full review often takes a few days, and your urologist will discuss results and treatment at a follow-up visit, often within 1 to 3 weeks.

Sources this page draws on

American Urological Association and Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction, Adult Urodynamics: AUA/SUFU Guideline (2012)
International Continence Society, Good Urodynamic Practices and Terms 2016
New England Journal of Medicine, A randomized trial of urodynamic testing before stress-incontinence surgery (the VALUE trial) (2012)
American Urological Association and Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction, Diagnosis and Treatment of Idiopathic Overactive Bladder: AUA/SUFU Guideline
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Urodynamic Testing

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.

Urodynamic testing

Overview

The parts of your body involved

Why it’s done

Other options

Getting ready

A week or so before

The day of

In the test room

The procedure, step by step

1. The flow test

After the procedure

Right afterward

At home

Recovery timeline

What it feels like

Before the test

The flow test

The catheters going in

The filling

Coughing and straining

Urinating with the catheter in

Afterward