Cystometric study

Definition

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.

Alternative Names

CMG; Cystometrogram

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:

• 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)

How the test will feel

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

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

Why the test is performed

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

Normal Values

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

What abnormal results mean

Abnormal results may be due to:

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

What the risks are

There is a slight risk of urinary tract infection and blood in the urine.

Special considerations

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.

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References

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.