Cystometric study measures the amount of fluid in the bladder when you first feel the need to urinate, when you are able to sense fullness, and when your bladder is completely full.
How the test is performed
You will be asked to void (urinate). The following will be recorded:
- The time it takes you to begin voiding
- The size, force, and continuity of your urinary stream
- The amount of urine
- How long it took you to empty your bladder
- Any straining, hesitancy, or dribbling that occurred
You lie down, and a thin, flexible tube (catheter) is gently placed in your bladder. The catheter measures any urine left in the bladder. A smaller catheter is then placed in your rectum, and measuring electrodes are placed near the rectum.
Next, heat sensation is measured. Room-temperature salt-water (saline) solution is placed into the bladder. This is followed by warm water. You will tell the health care provider what, if any, sensations you feel. The water is then drained from the bladder.
A tube used to monitor bladder pressure (cystometer) is attached to the catheter. Water or carbon dioxide gas flows into the bladder at a controlled rate. You will be asked to tell the provider when you first feel the need to urinate.
You may be asked to cough or push so that the health care provider can check for urine leakage. When the bladder is full, you will be told to urinate. The pressure of your urine flow is recorded.
The bladder is again drained of any urine or water, and the catheter is removed.
In some cases, x-rays are taken during the test. This is called videourodynamics.
How to prepare for the test
No special preparations are necessary for this test.
For infants and children, preparation depends on the child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
How the test will feel
There is some discomfort associated with this test. You may experience:
- Bladder filling
- Urgent need to urinate
Why the test is performed
The test will help determine the cause of bladder voiding dysfunction.
Normal values vary and should be discussed with your health care provider.
What abnormal results mean
Abnormal results may be due to:
What the risks are
There is a slight risk of urinary tract infection and blood in the urine.
This test should not be done if you have a known urinary tract infection. Existing infection increases the possibility of false test results. The test itself increases the possibility of spreading the infection.
Peterson AC, Webster GD. Urodynamic and videourodynamic evaluation of voiding dysfunction. In: Wein AJ, ed. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 58.
Bradley CS, Smith KE, Kreder KJ. Urodynamic evaluation of the bladder and pelvic floor. Gastroenterol Clin North Am. 2008 Sep;37(3):539-52, vii.
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Scott Miller, MD, Urologist in private practice in Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.