Urodynamic testing can show your urologist the following:
- The bladder's ability to store urine
- Your bladder's ability to empty steadily and completely
- Your sphincter control or weak sphincter muscles.
- If the bladder is having abnormal contractions that cause leakage.
- Help identify limited bladder capacity
- Identify bladder over activity or under activity
- Urinary obstruction
- The pressure in the bladder as it is filled with fluid through a small catheter.
- If the test is performed with EMG surface pads, it can also detect abnormal nerve signals and uncontrolled bladder contractions.
Preparing for the Tests
Uroflowmetry (Measurement of Urine Speed and Volume)A uroflowmeter automatically measures the amount of urine and the flow rate — that is, how fast the urine comes out. You may be asked to urinate privately into a toilet that contains a collection device and scale. This equipment creates a graph that shows changes in flow rate from second to second. Results of this test will be abnormal if the bladder muscle is weak or urine flow is obstructed.Measurement of Post Void ResidualAfter you have finished urinating, you may still have some urine, usually only an ounce or two, remaining in your bladder. This leftover urine is called post void residual.Your urologist can measure this residual using a catheter or ultrasound treatment to see if you are completely emptying your bladder when you urinate. A large amount of leftover urine may mean that you have an obstruction or blockage in your urinary tract or a problem with your bladder nerves or muscles.Cystometry (Measurement of Bladder Pressure)A cystometrogram (CMG) measures how much your bladder can hold, how much pressure builds up inside your bladder as it stores urine, and how full it is when you feel the urge to urinate.
- The doctor will use a catheter to empty your bladder completely
- Then a special, smaller catheter with a pressure measuring device called a manometer will be placed in the bladder
- Your bladder will be filled slowly with warm water. During this time you will be asked how your bladder feels and when you feel the need to urinate
- The volume of water and the bladder pressure will be recorded
Measurement of Leak Point PressureWhile your bladder is being filled for the cystometrogram (CMG), it may suddenly contract and squeeze some water out without warning. The manometer will record the pressure at the point when the leakage occurred. You may also be asked to apply abdominal pressure to the bladder by coughing, shifting position, or trying to exhale while holding your nose and mouth to help evaluate your sphincter muscles.Pressure Flow StudyA catheter can measure bladder pressure and urine flow rate as you void. A pressure flow study may identify bladder outlet obstructions caused by a prostrate enlargement. Bladder outlet obstruction is less common in women but can occur with a fallen bladder or rarely after a surgical procedure for urinary incontinence.ElectromyographyTo test whether your urinary problem is related to nerve or muscle damage, you may be given an electromyography. This test uses special sensors to measure the muscle activity in and around the urethral sphincter. The patterns of the impulses will show whether the messages sent to the bladder and urethra are coordinated correctly.Video UrodynamicsYour urologist may use x-rays or sound waves to create images of your bladder as it fills and empties to help identify the nature of your problem.