Cystometry

Test Overview

Cystometry is a test that measures the pressure inside of the bladder to see how well the bladder is working. Cystometry is done when a muscle or nerve problem may be causing problems with how well the bladder holds or releases urine.

Urination is a complex process. As the bladder fills, nerves in the bladder wall send a message to the spinal cord and brain that you need to urinate. In response, your spinal cord sends a signal for the bladder to contract (voiding reflex). When you hold in your urine, your brain is overriding this reflex. When you allow the reflex to occur, urination occurs. A problem affecting this nerve pathway or the muscles of the bladder wall can cause bladder dysfunction.

During cystometry, your bladder is filled with water to measure its ability to hold in and push out the water. Medicine may also be given to see whether your bladder contracts or relaxes normally in response to the medicine. A small tube (catheter) can be placed in your rectum to measure pressure as the bladder fills. A small pad or needle may be placed near your anus to measure muscle function in this area.

Why It Is Done

Cystometry is done to:

• Find the cause of problems with the bladder or the muscle that holds urine in the bladder (bladder sphincter). Problems in one or both of these areas may cause uncontrolled urine leakage, an urgent feeling that you have to urinate, or a weak urine stream.
• Measure how much urine your bladder can store and how much urine remains in your bladder after you feel you have completely emptied it (residual volume).
• Help you and your doctor make decisions about how to treat your urinary symptoms.
• See how well the bladder works in people with progressive neurological diseases, such as multiple sclerosis.

How To Prepare

You will need to drink enough fluids and avoid urinating so that you will be able to give a urine sample. Tell your doctor if you are having symptoms of a urinary tract infection or bladder infection.

How It Is Done

Cystometry is done in a doctor's office.

You will need to take off most of your clothes below the waist. You will be given a cloth or paper covering to use during the test.

• At the start of the test, you will be asked to urinate into a toilet that is connected to a machine called a uroflowmeter. This machine measures how much urine passes and how long it takes. The time and effort needed to start the flow of urine, the number of times you start and stop the flow of urine, and the presence of dribbling near the end of urinating are also recorded.
• Next, you will be asked to lie on your back on an examining table. After the urethra is thoroughly cleaned, a well-lubricated, thin, flexible tube (catheter) is gently inserted and slowly moved into your bladder. Any urine left in your bladder (residual volume) will be drained and measured.
• Next, a catheter is used to fill your bladder with sterile, room-temperature water. The catheter is also attached to a device called a cystometer. This will measure how much your bladder can hold and the pressure in your bladder. You will be asked to report any feelings such as warmth, bladder fullness, or an urge to urinate. The process may be repeated. If X-rays are taken during the test, a contrast material may be used.
• Another catheter may be placed in your rectum to measure the pressure in your abdomen as your bladder fills. A small pad or needle may be placed near your anus to measure muscle function in this area.
• Each time your bladder is filled, you will be asked to report when you first feel the urge to urinate. Your bladder will then continue to be filled until you report that you feel you must urinate. Then the catheter will be used to drain the bladder, or you will be asked to urinate.
• After all the liquid is drained out of your bladder, and if no more tests are required, the catheter is removed.

Other possible tests

While the catheter is in place, another test may also be done to help find out if the nerves that control urination are working properly.

• Leak point pressure (LPP). About 200 mL (7 fl oz) of sterile water is injected into the catheter in your bladder. The pressure is then measured while you bear down (as if having a bowel movement). This test helps find out whether the muscles around the bladder and urethra are working properly. A low pressure reading may mean that poor muscle function is causing urinary incontinence.
• Stress incontinence test. In this test, your bladder is filled with water and the catheter is withdrawn. You are then asked to cough, bend over, or lift a heavy object. Dribbling urine means stress incontinence.

How long the test takes

Cystometry testing usually takes 30 to 60 minutes. But it may take slightly longer if any of the special tests are done.

How It Feels

You may feel embarrassed at having to urinate in front of other people. This procedure is quite routine for the medical staff. If you find yourself feeling embarrassed, take deep, slow breaths and try to relax.

You will feel a strong urge to urinate at times during the test. You may also find it somewhat uncomfortable when the catheter is inserted and left in place, and you may be sore afterward. If so, soaking in a warm tub bath may help.

Risks

Cystometry usually doesn't cause problems. There is always a slight risk of getting a urinary tract infection when a catheter is inserted into the bladder. In rare cases, a bladder infection can spread to a kidney and into the blood, leading to a life-threatening infection. If an infection occurs, it can be treated with antibiotics.

Results

Some results may be available right away. Full results are usually available in 1 to 2 days.

Normal:

• The rate at which urine flows from your bladder when you urinate is normal.
• There's a normal amount of urine left in your bladder after you urinate (residual urine volume).
• The point at which you first feel the urge to urinate is within the normal range.
• The point at which you feel you must urinate is within the normal range, when the amount of liquid in your bladder is between 350 and 500 mL.
• The maximum amount of liquid your bladder can hold is within the normal range.
• Tests of the function of the nerves that control your bladder are normal.
• Urine does not leak from your bladder during the stress test.

Abnormal:

• The rate at which urine flows from your bladder when you urinate is slower than normal, or your urine stream starts and stops.
• The amount of urine left in your bladder after you urinate (residual urine volume) is more than normal.
• You have trouble starting the flow of urine.
• The point at which you first feel the urge to urinate is more or less than normal or does not occur.
• The maximum amount of liquid your bladder can hold is less than or greater than normal.
• Normal sensations and reactions do not occur when the nerves that control your bladder are tested.
• Urine leaks from your bladder during the stress test.