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.

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 and records any urine left in the bladder. A catheter is then placed in your rectum, and measuring electrodes are placed near the rectum (perineum).

Next, thermal 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 then connected to the catheter. Water or carbon dioxide gas is introduced into the bladder at a controlled rate. You will be asked to tell the provider when you first feel the need to urinate. When the bladder is full, you must urinate. The pressure of this urination is recorded.

The bladder is again drained of any urine or water, and the catheter is removed.

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:

• Preschooler test or procedure preparation (3 to 6 years)
• School age test or procedure preparation (6 to 12 years)
• Adolescent test or procedure preparation (12 to 18 years)

There is some discomfort associated with this test. You may experience:

• Bladder filling
• Flushing
• Nausea
• Pain
• Sweating
• Urgent need to urinate

The test will help determine the cause of bladder voiding dysfunction.

Normal values vary and should be discussed with your health care provider.

The test might indicate a cause for:

• Enlarged prostate
• Multiple sclerosis
• Overactive bladder
• Reduced bladder capacity
• Spinal cord injury
• Stroke
• Urinary tract infection

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.