How Is a Urodynamic Test Performed?

Reviewed on 8/24/2022

Model of a bladder
Urodynamic testing involves several types of tests, which include uroflowmetry, postvoid residual urine measurement, cystometric test, leak point pressure measurement, pressure flow study, electromyography, and video urodynamic tests. 

There are several different types of urodynamic tests, which include uroflowmetry, postvoid residual urine measurement, cystometric test, leak point pressure measurement, pressure flow study, electromyography, and video urodynamic tests.

Each type of urodynamic test is performed differently. Urodynamic tests are conducted in the following ways: 

  • Uroflowmetry
    • Measures how much urine is in the bladder and how fast urine comes out (flow rate), which can show if bladder muscles are weak or if urine flow is blocked
    • In this test, patients urinate into a special toilet or funnel with two parts:
      • A container to collect the urine 
      • A scale
    • A graph is created that shows changes in the flow rate as the patient urinates
    • The graph is used to see when the flow rate is highest and how many seconds it takes to get there
    • The flow rate can also be measured by recording how long it takes to urinate into a special container that accurately measures how much urine is released
  • Postvoid residual urine measurement
    • Measures how much urine is left in the bladder after urination
    •  If 100–150 milliliters or more of urine remains in the bladder then the bladder is not emptying completely
    • May be conducted using ultrasound or by feeding a catheter into the bladder to drain and measure remaining urine
  • Cystometric test
    • Measures:
      • The amount of urine the bladder can hold
      • How much pressure builds up inside the bladder as it stores urine
      • How full the bladder is when the urge to urinate starts
    • A catheter is used to completely empty the bladder, after which a special, smaller catheter has a pressure-measuring device (called a manometer) is placed in the bladder
    • Once the bladder is completely emptied, it is filled slowly with warm water and patients are asked describe how the bladder feels and when they feel the need to urinate
    • When the patient feels the urge to urinate, the volume of water and the bladder pressure are recorded
    • This test can also tell if the bladder contracts when it’s not supposed to
    • A leak point pressure measurement or a pressure flow study may be done at the same time
  • Leak point pressure measurement
    • While the bladder is filled with warm water for a cystometric test, it may suddenly contract and squeeze some water out without warning
    • A pressure-measuring device called a manometer measures the pressure inside the bladder when this occurs, which is the leak point pressure that can help identify the kind of bladder problem that is present
  • Pressure flow study
    • Measures the amount of pressure the bladder needs to urinate and how quickly urine flows at that pressure
    • After a cystometric test, a patient empties the bladder while a manometer measures bladder pressure and flow rate
    • This study can help identify bladder outlet blockage that may be caused by: 
  • Electromyography
    • May be recommended if a urinary problem is thought to be related to nerve or muscle damage
    • This test uses special sensors to measure the electrical activity of the muscles and nerves in and around the bladder and sphincters
    • Sensors are placed on the skin near the urethra and rectum or on a urethral or rectal catheter and muscle and nerve activity is recorded 
    • The patterns of the nerve impulses show whether the messages sent to the bladder and pelvic floor muscles are coordinating correctly
  • Video urodynamic tests
    • Uses X-rays or ultrasound to take pictures and videos of the bladder as it fills and empties
    • A catheter may be used to fill the bladder with contrast or dye for a better picture

What Is a Urodynamics Test?

Urodynamic testing refers to several procedures used to check how well the lower urinary tract (bladder, sphincters, and urethra) functions to hold and empty urine. Urodynamic tests can also show if the bladder contracts when it’s not supposed to, resulting in urine leakage.

Who Needs a Urodynamic Test?

Urodynamic testing may be recommended if a person:

  • Leaks urine
  • Goes to the bathroom frequently
  • Feels pain while urinating
  • Feels a sudden, strong urge to use the bathroom
  • Has trouble starting to urinate
  • Has problems emptying your bladder completely
  • Has repeated urinary tract infections (UTIs)

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Reviewed on 8/24/2022
References
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Image source: iStock Images

https://www.niddk.nih.gov/health-information/diagnostic-tests/urodynamic-testing