Cystometric Study

Written by Ann Pietrangelo | Published on August 15, 2012
Medically Reviewed by George Krucik, MD

What is a Cystometric Study?

A cystometric study is used to determine the size and functionality of your bladder. It measures how much fluid your bladder can hold, how full it is when you begin to feel the need to urinate, and the pressure of your urine stream.

Your doctor may want you to undergo this procedure if you have trouble completely emptying or controlling your bladder.

Cystometric studies require no preparation. You may experience discomfort during the procedure, which carries some risk of urinary tract infection.

Cystometric studies are sometimes referred to as “cystometrograms” or “CMGs.”

What Cystometric Studies Can Show

Bladder dysfunction can cause embarrassment and have a significant impact on your quality of life. Cystometric studies help to measure the bladder and analyze how it works. This can assist your doctor in identifying specific problems and recommending treatments that will improve your ability to carry on with normal daily activities.

Bladder problems, including overactive bladder, reduced bladder capacity, and inability to completely empty the bladder are associated with a variety of conditions, such as:

How a Cystometric Study Is Performed

A cystometric study can be performed in a doctor’s office, an outpatient clinic, or a hospital. General anesthesia is not required. CMG should not be done if you have an active urinary tract infection, as this procedure may cause your infection to spread to the bladder.

Before the Procedure

Your doctor may prescribe antibiotics before or after the procedure to help prevent infection. Exactly how the test is performed will vary slightly based on the doctor, the facility, and your medical condition. Your doctor will provide details specific to your procedure.

During the Procedure

You may be instructed to empty your bladder so the technician can record:

  • how long it takes you to start urinating
  • the size and strength of your stream
  • how long it takes to empty your bladder
  • the amount of urine you produce

Any difficulties or abnormalities will be recorded.

The test will take place while you are lying on your back on a bed or examination table. The skin around your urethra will be cleaned and a local anesthesia may be used.

A healthcare professional will insert a catheter (a thin tube) into your urethra and up into your bladder. This sometimes causes a slight burning sensation. The catheter will measure how much urine is still in your bladder.

A second catheter will then be inserted into your rectum, with electrodes placed in the surrounding area. A cystometer (a tube attached to the catheter) is used to gauge pressure.

Your bladder will be filled with a saline solution and water. You will be asked if you feel fullness, pressure, pain, or an urge to urinate. You may also feel the sensation of coolness or warmth from the liquid. It is possible that your bladder may leak a little during the procedure. This is normal.

As your bladder fills, the technician will ask you to report when you begin to feel an urge to urinate. After your bladder is full, you will urinate while the pressure of your urine stream is recorded.

Any fluid still in your bladder will be drained and the catheters will be withdrawn.

The entire procedure will take about 15 to 30 minutes to complete.

Side Effects and Risks

During the Procedure

Depending on your medical condition, you may experience some pain during the procedure. Most people report discomfort when the catheter is inserted and when the bladder is filled. You may feel an urgent need to urinate. Other potential side effects include nausea, sweating, and flushing.

For people who have a high spinal cord injury, there is a risk of autonomic dysreflexia, an abnormal response to the pressure of a full bladder. Symptoms include:

  • sweating
  • feeling flushed
  • headache
  • high blood pressure.

This is a dangerous condition that can cause seizure, stroke, or even death. If you begin to have some of these symptoms during the test, tell the doctor immediately.

After the Procedure

You may have some discomfort during urination for a few days, and your urine might contain small amounts of blood. Urinary tract infection is also reported in some patients. If you experience fever, chills, excessive bleeding, or increasing pain, this may be a sign of infection and you should contact your doctor immediately.

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