Cystometric study measures the amount of fluid present 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.
Why the CMG is Performed
The test will help determine the cause of bladder-voiding dysfunction.
How the CMG is Performed
You will be asked to void (urinate). The time it takes you to begin voiding, and the size, force, and continuity of your urinary stream will be recorded. The amount of urine, how long it took you to empty your bladder, and any straining, hesitancy, or dribbling that occurred are recorded.
You lie down, and a thin, flexible tube (catheter) is gently positioned in your bladder to measure and record 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 saline solution is placed into the bladder, 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 a tube used to monitor bladder pressure (cystometer) is then connected to the catheter. Water or carbon dioxide gas is slowly 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, and the pressure of this urination is recorded.
The bladder is again drained of any urine or water, and the catheter is removed.
How to Prepare for the CMG
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)
- Schoolage test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
How the CMG Will Feel
There is some discomfort associated with this test. You may experience pain, flushing, sweating, nausea, bladder filling, and an urgent need to urinate.
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, and the test itself increases the possibility of spreading the infection.
Normal values vary and should be discussed with your health care provider.
What Abnormal Results Mean
The test might indicate a cause for urinary tract infection, diminished bladder capacity, multiple sclerosis, stroke, spinal cord injury, bladder outlet obstruction such as benign prostatic disease, or overactive bladder.