How Is a Urodynamic Test Performed?

Urodynamic tests include:

• Cystometry
• Electromyography
• Pressure flow study
• Uroflowmetry
• Postvoid residual measurement
• Video urodynamic test

A cystometric test or cystometrogram measures the pressure inside the bladder using a catheter. The test reveals how much a bladder can hold, how elastic the bladder is, and how full it is when the urge to urinate begins. The catheter consists of a pressure measuring device known as the manometer. The bladder is emptied using a catheter. After emptying the bladder, it is slowly filled with warm water. When the bladder fills and the urge to urinate starts, the manometer records the pressure point of leakage. The person needs to cough or strain to measure any bladder changes.

Electromyography adopts special sensors to measure the electrical activity of the muscles and nerves in and around the bladder and the sphincters. This is usually done when the urinary problem is associated with nerve or muscle damage. The sensors placed on the skin near the urethra and rectum records the electrical currents during the contraction of muscles. Any abnormality in the patterns of the nerve impulses can be easily detected through this technique.

Pressure flow study measures the bladder pressure required to urinate and the flow rate a given pressure generates. This study is carried in continuation with the cystometric test, where during the bladder emptying, a manometer measures the bladder pressure and the flow rate. It also helps to identify any blockage in the bladder outlet that men usually experience with prostate cancer. In women, bladder outlet blockage can rarely occur either with a cystocele or after surgery for urinary incontinence.

Uroflowmetry is the measurement of urine speed and volume. It includes a device for determining the speed and amount of urine and a computer to record the data. During this test, the person has to urinate into special equipment that will allow measurements of urine speed and volume. The computer creates a graph to determine any changes. This test helps to identify a weak bladder or any kind of blockage.

Postvoid residual measurement test measures the amount of urine left in the bladder after passing urine. The residual urine is known as the postvoid residual. It utilizes ultrasound equipment that uses harmless sound waves to create an image of the bladder. The physician inserts a thin, flexible tube (catheter) through the urethra up into the bladder to remove and measure the residual urine. A postvoid residual of 100 millimeters or more is a sign of an incomplete bladder emptying.

Video urodynamic tests take pictures and videos of the bladder during the filling and emptying. It uses X-rays or ultrasound equipment to measure the urine flow and pressure in the bladder or rectum. This test provides useful information about bladder and urethral function and reveals the size and shape of the bladder. While performing an x-ray, the healthcare provider fills the bladder with a contrast medium that shows up on x-rays. If ultrasound equipment is used, the bladder is filled with warm water and harmless sound waves create an image of the bladder.

After the tests, a person may experience mild discomfort for a few hours while urinating. Drinking an eight-ounce glass of water every half hour for 2 hours may ease the discomfort. The physician may prescribe an antibiotic for 1 to 2 days to prevent infection.