Urodynamic Studies

Urodynamic Study

Urinary System

What is an urodynamic study?

A urodynamic study is when a special machine is used to look at how the bladder, urethra, and sphincter (muscle) work.

The bladder is the part of your child’s body that stores urine. When it is time for the bladder to empty, the sphincter (muscle) relaxes and the bladder squeezes the urine out. Once the bladder is empty, the sphincter tightens and the bladder relaxes and starts to refill. The urethra is the tube the urine flows through from the bladder to the outside of the body.

Problems passing urine can be due to either the storage or emptying of urine from the bladder. This can be caused by:

  • Conditions of the nervous system
  • Blockage of the urethra
  • Bladder muscle dysfunction
  • Side effects of medicines (i.e., cold medicines, tranquilizers)
The tests that may be done in the Urodynamic Study include:
  • The uoflow study checks how well your child passes urine by measuring the amount of urine passed and the time it takes to pass it. Your child should have a full bladder and will need to pass urine into a special toilet after the machine is turned on.
  • The cystometrogram (CMG) tests how well your child’s bladder muscle stretches, the amount of urine the bladder holds, how well your child can feel it filling and the pressure in the bladder needed to cause a stream and expel the urine. A catheter will be placed in your child’s bladder, if one is not already in place, for the uroflow study. The tube will be attached to a machine that will fill your child’s bladder with water. Your child will be asked certain questions during this test, such as, “Do you feel the need to pass urine”? X-rays may be taken during this study. The CMG will show how much urine your child’s bladder holds before he/she feels the need to pass urine.
  • A sphincter electromyogram (EMG) is done to show how well your child’s sphincter muscles are working and if they are working with the bladder muscle. Special patches will be placed on your child’s bottom. This will record the muscle activity while your child’s bladder is being filled or emptied. It allows us to "hear" your child’s muscles working.

What to expect after the test:

  • Your child may have slight discomfort after the test when he/she passes urine. Warm baths may be helpful.
  • Your child will need to drink lots of fluids for one day.