What is a urodynamics study?
The urodynamics study is a test used to assess how well your child's bladder and urethral sphincter are doing their jobs of collecting, holding and releasing urine.
- Normally, muscles and nerves of the urinary system work together to control the release of urine. Nerves carry messages from the bladder to the spinal cord and then to the brain, as well as messages from the brain to the muscles of the bladder and sphincter, telling them either to tighten or release.
- Urodynamics testing is an excellent way to evaluate how the bladder carries out its two main functions: filling and emptying.
What happens during the test?
Your child's urine flow is measured as he or she urinates in a special, privately placed toilet. Then a thin, flexible tube is placed in your child's bladder to fill it slowly with a warm saltwater solution. At the same time, bladder pressures are monitored and the presence or absence of premature bladder contractions is noted, along with any sensations experienced by your child. Other aspects of the bladder that are monitored include its emptying characteristics (whether or not the bladder empties completely with normal pressures, high pressures or low pressures).
The study can have as many as five parts:
- Urinary flow rate (also known as the Uroflow): Your child will be asked to urinate in a special toilet that is attached to a computer that records the actual flow of urine. It measures second-by-second flow and the total volume of urine.
- Catheterization: A thin flexible plastic tube called a catheter will be gently inserted into your child's urethra and advanced into the bladder to drain any urine left in it. Then it is taped loosely so it won't come out during further testing.
- Urethral pressure profile (UPP): The catheter is slowly drawn through the urethra, while a computer measures pressures in the urethra.
- Cystometrogram (CMG): The bladder is filled with warm saltwater through the catheter and, when the bladder is full, your child will need to urinate with the catheter in place so that the computer can continue to record pressures. This lets doctors monitor bladder pressures.
- Electromyogram (EMG): If your pediatric urologist suspects a neurological cause for your child's condition, an EMG will likely be recommended. For this part of the test, an electrode is placed into the external urinary sphincter muscle. The doctor will record your child's sphincter muscle reflexes and responses when the bladder is filled and emptied.
Who should undergo urodynamics testing and when should testing occur?
Children with urinary incontinence may need a urodynamic study if the problem hasn't been fixed by simpler methods of treatment, such as drugs to help achieve dryness and behavioral modification strategies.
- For children with recurring urinary infection, urodynamics studies are usually performed after the child has been on continued long-term antibiotics, but is still having episodes of incontinence or recurring infection.
- The studies may also be necessary when x-ray imaging reveals particular abnormalities of the bladder in children who have had multiple urinary infections.
- Studies may also be performed when imaging studies reveal changes in the appearance of the upper urinary tract, which suggests an alteration in bladder function.
For children with known neurological conditions, such as myelodysplasia, the studies are usually performed during the newborn period, so that therapy can be initiated as soon as possible. Studies are also needed when these children are older, if they haven't achieved continence with simple measures of intermittent catheterization and drugs that help paralyze the bladder.
In children with anatomic conditions that lead to incontinence, such as bladder exstrophy/epispadias or anorectal malformations, urodynamics studies are recommended as soon as the diagnosis is made and after initial treatments fail to correct the incontinence. Testing helps guide the pediatric urologist toward other means of therapy and improves the efficiency of your child's treatment plan.
How do I plan for the testing?
To be sure that your child does not have a urinary infection at the time of testing, your pediatric urologist will want to obtain a urine culture approximately one week before the scheduled date.
On the day of the test, it is important to make sure that your child comes to the urodynamics suite with a relatively full bladder (if toilet trained) so that he or she can urinate voluntarily. A full bladder is not crucial for children who cannot void voluntarily and require catheterization to empty the bladder.
It is also important to prepare your child, explaining why the test is important, what it is designed to accomplish and how it might improve your child's health. Understanding the purpose of the test and all of its aspects is likely to make the testing easier for your child.
Why Boston Children's Hospital uses urodynamics testing
By tracking how the bladder fills and empties, physicians can get clues to why a child may have urinary incontinence or urinary infections. Urodynamics testing can also assess any abnormalities of the upper urinary tract.
A urodynamics study is usually performed when the following conditions are suspected or diagnosed: