AUA Summit - What is a Cystometry/Cystometrogram (CMG)?


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What is a Cystometry/Cystometrogram (CMG)?

Cystometry, or cystometrogram, with a pressure flow study is part of urodynamic testing (or UDS). These tests measure how well the bladder functions. They help diagnose problems related to urine control. These can be incontinence, difficulty emptying the bladder, overactive bladder, obstructions or frequent infections.

Cystometry is used to measure how much urine the bladder can hold. It also measures pressure inside the bladder, and how full it is when you have the urge to go.

What to Expect

There is nothing special needed to prepare for this test. Some people are asked to stop certain medicine before the test. Sometimes antibiotics are given before you start. This is done to prevent infection.

Before the test, you will be asked to empty your bladder as much as you can. A small soft tube (called a catheter) is inserted into the urethra until it reaches your bladder. The catheter allows the bladder to be emptied completely. It is also used to measure the amount of urine remaining in the bladder after you go. Plus, it measures the strength of your bladder by recording pressure.

Another small catheter, about the size of a soft spaghetti noodle, is placed into the rectum. This catheter is used to measure pressure on the outside of the bladder in the abdomen.

The bladder is then slowly filled with liquid (usually sterile water, sterile saline, or a sterile fluid). This liquid includes a dye that can be seen on x-ray. You will be asked to describe what you feel in your bladder. Does it feel cool? Do you feel full? Does it hurt? You may be asked to cough or bear down to see if there are leaks.

When you feel a full bladder and you need to urinate, you will do so in a special toilet. You will go while the special catheters and sensors are in place. This allows your health care provider to measure pressure as you urinate. This part of the test is called a Voiding Pressure Study (pressure flow study).

For about one day after the study, some people feel a sense of burning or pain when they urinate or may see blood. This will go away. If you continue to see blood in your urine or have a fever, please tell your doctor.

More Information

  • What are results from this test telling you?
  • Will I need other tests to explain my problem?
  • What are my next-steps for treatment?

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