How do urodynamic tests work?
Each type of urodynamic test works a little differently. Your healthcare provider may even perform multiple tests at one time to get the best understanding of how your urinary system is working.
Cystometry
A cystometric test, or a cystometrogram, is a test that uses catheters (thin, flexible tubes) to measure pressure inside your bladder. The test can tell:
- How much pee your bladder can hold.
- How much pressure your bladder is under when it stores your pee and how quickly that pressure rises while your bladder fills.
- How full your bladder is when you feel the urge to pee.
The test can also measure contractions or spasms of your bladder wall while your bladder is filling.
In a cystometric test, you begin with an empty bladder. Your healthcare provider inserts a small catheter into your bladder through your urethra. This catheter has a sensor called a manometer on it, which can measure bladder pressure throughout the study. Your provider may also insert a second catheter into your vagin* or rectum to measure pressure inside your abdomen.
Then, they slowly fill your bladder with a warm, sterile solution. You might be asked to cough or strain while your bladder is filling so that the point of pressure (leak point pressure) can be recorded. At the end of a cystometrogram, you’ll be asked to empty your bladder. The manometer will measure the pressure of your bladder and your flow rate (pressure flow measurement).
Some people may find it difficult to empty their bladders with a catheter or with another person in the room. Don’t be embarrassed if this happens. While you might feel your healthcare provider inserting the catheter into your urethra, the test doesn’t hurt.
In men and people assigned male at birth (AMAB), the results of this test might indicate an enlarged prostate, which can make it difficult to pee.
Electromyography
Electromyography uses sensors to measure the electrical activity of the muscles and nerves in and around your bladder and sphincters. The test uses electrode patches near your urethra and rectum to record electrical currents when muscles in your pelvic floor contract.
Uroflowmetry
Another test that measures how much and how quickly you pee is uroflowmetry. For this test, your provider will ask you to have a full bladder when you come to the office. You’ll pee into a machine (sort of like an electronic toilet) that automatically measures the amount and flow rate of your pee, creating a graph that shows any changes. Test results will indicate that you may have weak bladder muscles or some kind of blockage causing your stream of urine to be weak or intermittent.
Postvoid residual measurement
The postvoid residual measurement test measures the amount of pee left in your bladder after you empty it. The urine that’s left is called thepostvoid residual and everyone has a tiny bit left after they pee. Your healthcare provider typically uses an ultrasound to create a picture of your bladder (called a bladder scanner).
People with certain medical conditions may not be able to have a bladder scan. In these cases, postvoid residual can also be tested by using a catheter that’s placed into your urethra and then into your bladder to remove the excess urine. A postvoid residual of 5 to 6 ounces (oz) or more is a sign that your bladder isn’t emptying completely, but this can vary. Your healthcare provider will review the results with you.
Video urodynamic tests
Video urodynamic tests combine cystometry, uroflowmetry and X-ray cystography into a single test. The digital equipment healthcare providers use in this test can measure urine flow and pressure in your bladder and rectum by using X-rays. The equipment takes images of your bladder during filling and emptying. These tests provide useful information about bladder and urethral function and show the size and shape of your bladder. If X-rays are done, your bladder will be filled with a fluid that contains contrast dye material, which makes the images show up more clearly. These contrast dyes typically don’t absorb into your body. However, people with a contrast dye allergy should always let their healthcare provider know about their allergy (and any others) before any procedure or treatment.
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Is there any preparation for urodynamic testing?
Most of the tests don’t require any special planning. For some, your provider may ask you to drink fluids before the test so that your bladder is full. Be sure to ask your healthcare provider any questions before the test or if you have to stop taking certain medications beforehand.
What happens after a urodynamic test?
You might have mild discomfort or soreness when you pee. This should only last a few hours. You might even see a small amount of blood in your pee. These symptoms might ease up if you drink 8 to 16 ounces of water every hour for two hours.
Your healthcare provider might also suggest taking a warm bath or holding a warm, damp washcloth over your urethral opening. You might also be told to take over-the-counter (OTC) pain medication if you need it.
In some cases, your provider might give you a prescription for an antibiotic to prevent infection, but this isn’t always necessary. If you have any symptoms of infection, such as a fever, chills or pain, you should call your healthcare provider immediately.
How long do urodynamic tests take?
The exact length of the test varies but you can expect it to take 30 to 45 minutes, on average.
What are the risks of urodynamic testing?
Urodynamic testing is extremely safe and reliable. There’s a small chance of developing a urinary tract infection due to inserting a catheter into your urethra.
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How painful is urodynamic testing?
Urodynamic tests shouldn’t be painful. You may feel soreness for up to 24 hours afterward, but you shouldn’t have severe pain.
Can you be sedated for urodynamic testing?
It’s usually not necessary for adults to receive sedation or anesthesia before urodynamic testing. But, if a child is having the test, very mild sedation may help relax them. It’s best to discuss concerns about sedation or anesthesia with your provider
