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 or gas to measure its ability to hold in and push out the water or gas. 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 leakage urination, a 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 indicate. 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 series of tests, 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 advanced into your bladder. Any urine remaining in your bladder (residual volume) will be drained and measured.
• 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.
• For cystometry, the 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 a urge to urinate. The process may be repeated.
  • Sometimes a gas (usually carbon dioxide) is used instead of water.
  • A contrast material may be used if X-rays are taken during the test.
• 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 you will be asked to urinate around the catheter. Any urine remaining in your bladder after you urinate will be drained by the catheter.
• After all the liquid is drained out of your bladder, and if no additional tests are required, the catheter is removed.