Urodynamic Tests

The urinary tract system consists of the two kidneys, two ureters and the bladder. It also includes the sphincter muscle that controls the flow of urine and the urethra, which brings urine from the bladder to outside the body. This is a test that tells us how the "lower urinary tract," the bladder, and urethra work.

How does the urinary tract system normally work?

The kidneys filter blood and make urine that flows from the kidneys through tubes called ureters to the bladder. The bladder holds the urine, and then releases it, when the sphincter muscle relaxes, through the urethra. Normally, as urine fills the bladder, it stretches to hold the increasing amounts at a low bladder pressure. When the bladder becomes full, a message is sent to the brain. Signals from the brain then tell the sphincter muscle when to relax, and the bladder when to squeeze, so the bladder can empty. The bladder must squeeze at the same time as the sphincter muscle relaxes. Normally, the individual can wait until the right time to empty the bladder.

What information will I get from these tests?

  • How much urine the bladder can hold
  • If the bladder is able to keep pressures low as it fills, holds, and releases urine. This is very important because high bladder pressures can cause kidney damage.
  • How well the bladder empties
  • If the bladder squeezes and the sphincter relaxes at the same time
  • If reflux (the backup of urine from the bladder to the kidneys) is present

Who may need urodynamic tests?

Children who have conditions that affect the bladder may need urodynamic tests at times to check how the bladder is working. These conditions include children with:

Neurogenic bladders or other birth defects such as:

  • Bladder exstrophy
  • Sacral agenesis
  • Spina bifida
  • Spinal cord injury
  • Posterior urethral valves

Significant voiding problems such as:

  • Persistent incontinence (wetting) who do not respond to standard treatment
  • Severe dysfunctional voiding

The tests cannot be done if your child is currently being treated for a urinary tract infection or if he/she has completed treatment for an infection within the past week. If this is the case, please call to have the test re-scheduled.

Who will perform the test?

The test will be done by a nurse and a doctor (pediatric urologist) who have special training in doing this test.

Preparing for the test

The nurse or doctor doing the test will explain to the parent and child what will be done. Parents are encouraged to stay with the child during the test. When the child arrives, he/she will be shown the equipment in the room. This includes X-ray equipment and a television screen where the child can look at his/her bladder.

It is important that the child be as relaxed as possible during the test. Having a book to read or having the child hold a favorite stuffed animal during the test may be helpful. Older children may want to bring a personal music player. Sedation is generally not given since it may affect the test results. Most children can be talked through this test. Also, the more relaxed the parent, the more relaxed the child will be.

How will the test be done?

Before the test, you will be asked about your child's medical history and his/her urinary habits. The child should have a full bladder at the beginning of the test. If the child is toilet trained, he/she may be asked to go to the bathroom or may be asked to urinate on a special commode that is attached to a computer that measures the flow of urine. Children performing clean intermittent catheterization do not need to come with a full bladder.

After this, the child will lie on a table. This test requires that a catheter, which is a small flexible tube, be placed in the bladder. The nurse will first wash the child's genitalia (between the legs). Then a jelly-type medicine may be used to numb the area. The catheter will then be put in the urethral meatus, the opening where your child urinates. Some children may help insert the catheter.

After this, the nurse drains and measures any urine left in the bladder. The bladder is then filled slowly with a clear fluid that has a material in it that will show up on an x-ray. As the bladder is filling, the pressures in the bladder are checked and other information is recorded on a computer. If the child is toilet trained, he/she is asked to tell the doctor when he/she feels the need to go to the bathroom. The child also needs to be observed, to see if leaking of urine occurs that the child may not be aware of. This is especially true in the young infant or toddler or a child with a known neurological problem affecting the bladder.

As the bladder is being filled, several x-rays will be taken to look for reflux, and to check on how the bladder and urethra look. When the bladder is full, or the child feels the need to void, he will be asked to urinate, while on the table. Films will also be taken as the bladder is emptying.

When the test is finished, the doctor will talk over the test results with you and make a treatment plan for your child.

If you have any questions before this test is done, please contact us.

Page reviewed on: Apr 29, 2009

Page reviewed by: Leslie T. McQuiston, MD