Cystometry

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

Tell your doctor if you:

• Are taking any medicines. Some medicines and herbal supplements can affect bladder function.
• Are or might be pregnant.
• Have symptoms of a urinary tract infection, such as pain or burning with urination, foul-smelling or cloudy urine, or an urge to urinate more often than usual.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).

How It Is Done

Cystometry is done in a doctor's office or hospital urology department by a urologist, gynecologist, or other trained health professional.

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 beginning 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 remaining 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, which measures 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. A contrast material may be used if X-rays are taken during the test.
• 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 additional tests are required, the catheter is removed.

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

• Leak point pressure (LPP). Approximately 200 mL (7 fl oz) of sterile water is injected into the catheter in your bladder, and then the pressures are 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.

Another test that may be done is the 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.

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

After cystometry, you will need to keep track of how much you drink and how much you urinate for the next 24 hours. A burning sensation during urination is a common but temporary side effect. Drinking lots of fluids will help relieve this sensation. You may be given an antibiotic to help prevent a urinary tract infection.

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.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Having a urinary tract infection (UTI). Cystometry should not be done if you have a UTI.
• Straining when urinating.
• Not being able to urinate while sitting or lying down.
• Not being able to urinate in front of other people.
• Taking medicines, such as antihistamines and cough and cold medicines, that interfere with your bladder function.
• Having surgery for a spinal cord injury within 6 to 8 weeks before this test.

What To Think About

Since the results of cystometry are often unclear, other tests such as cystourethrogram, intravenous pyelogram (IVP), ultrasound, or cystoscopy may also be needed.