Urodynamic testing is used to evaluate lower urinary tract function in people who are experiencing problems with urination, such as incontinence, and to pinpoint the cause of the problem. Any of the following studies may be included, singly or in combination.

Uroflowmetry is a simple, noninvasive test that utilizes an electronic recorder to measure the speed of urine flow (more precisely, the volume expelled from the bladder per second). If the rate is very slow, obstruction may be present along the urinary tract.

Cystometry (or a cystometrogram) involves instilling fluid through a catheter into the bladder and evaluating the bladder’s muscle and nerve function. Various parameters are measured, including the pressure within the bladder, the sensation of urgency that you feel when your bladder is filled, and muscle contractions by the bladder wall.

Urethral pressure profile, sometimes done as part of cystometry, uses a special probe to measure the pressures along the urethra, the canal through which urine flows from the bladder out of the body, and to locate any obstruction.

Pressure-flow studies measure bladder pressure and urine flow rate during urination by placing a recording device into the bladder and, in many cases, another into the rectum. A high pressure with a low urine flow indicates obstruction; low pressure with a low flow indicates a problem with the bladder itself, such as nerve or muscle dysfunction.

Electromyographic studies are used to evaluate the function of the external urinary sphincter and pelvic floor muscles, which help to control the outflow of urine from the bladder. Several sensors, or electrodes, are used to measure the electrical activity of these muscles at rest, during contraction, and during urination. These tests are usually done simultaneously with cystometry and pressure-flow studies.

Video urodynamic studies combine the use of real-time x-rays, or fluoroscopy, with cystometry and pressure-flow studies. Instead of a fluid such as saline, the bladder is filled with a liquid contrast dye that appears opaque on x-rays and delineates the bladder and urethra on the images. This procedure is reserved for complex cases or when the more standard tests have not yielded satisfactory results.

Purpose of the Urodynamic Testing

  • To evaluate lower urinary tract function and determine the type and nature of urinary dysfunction in people with incontinence and other urinary problems

Who Performs Urodynamic Testing

  • A doctor, a nurse, or a lab technician

Special Concerns about Urodynamic Testing

  • Certain medications may alter the results of several urodynamic tests.
  • Cystometry, urethral pressure profile, pressure-flow studies, and video urodynamic studies should not be done in people with an active urinary tract infection.
  • Movement during electromyographic studies may distort the recordings.
  • Pregnant women should not undergo video urodynamic studies because exposure to ionizing radiation may harm the fetus.

Before the Urodynamic Testing

  • Report to your doctor any medications, herbs, or supplements you are taking. You may be advised to discontinue certain of these agents before the test.
  • Before uroflowmetry, do not urinate for several hours and increase your intake of fluids so that you have a full bladder when the test begins.
  • Before video urodynamic studies, be sure to tell your doctor if you are possibly pregnant or have a known shellfish or iodine allergy or have ever had an adverse reaction to x-ray contrast dyes.

What You Experience during Urodynamic Testing

Uroflowmetry:

  • You will be escorted to a private room with a special uroflowmetry commode that measures the flow rate as you urinate.
  • You are left alone. After pushing the start button and waiting for 5 seconds, you should begin to urinate. When you are finished, count to 5 and press the button again.
  • To maximize the accuracy of results, remain still as you urinate and avoid straining.
  • The test takes about 10 minutes.

Cystometry:

  • Just before the procedure, you will be asked to urinate.
  • You will lie down on an examining table.
  • A thin, soft tube, or catheter, is carefully passed through your urethra and into the bladder, and any residual urine is measured and recorded.
  • After the fluid is drained from your bladder, the catheter is connected to a device called a cystometer, which monitors bladder pressure.
  • Next, saline solution or water (or in some cases carbon dioxide gas) is slowly introduced into the bladder at a controlled rate, usually while you are in a seated position. During this process, bladder pressures are recorded.
  • The doctor will ask you to indicate when you first feel the urge to urinate and then when you feel urgency, indicating your bladder is full.
  • You may be asked to cough or strain to determine the presence of any leakage.
  • The fluid is then drained and the catheter removed if no additional tests are required.
  • The test usually takes about 45 minutes.

Urethral pressure profile:

  • A catheter is gently inserted through your urethra and into your bladder, and attached to a machine that monitors pressure.
  • Fluids or gas are instilled through the catheter. As the catheter is withdrawn slowly, pressures along the urethral walls are measured.
  • A syringe pump maintains a constant infusion of the fluids or gas.
  • The catheter is removed.
  • The test usually takes less than 15 minutes.

Pressure-flow studies:

  • You will lie down on an examining table, with your knees bent and feet resting in stirrups.
  • A catheter equipped with a special pressure sensor is gently inserted through the urethra into the bladder. A similar device may be inserted into the rectum.
  • Fluid is instilled through the catheter to fill the bladder. You should report when you first feel the urge to urinate, and when the sensation becomes urgent.
  • When you feel a strong urge to urinate, you will be instructed to urinate around the catheter.
  • The catheter(s) are withdrawn.
  • The test takes about 10 minutes.

Electromyographic studies:

  • You will lie down on an examining table.
  • A special paste is applied, and several electrodes are taped in place on the skin; they are typically placed in the area around the urethra in women and around the anus in men. An additional electrode that serves as a ground is usually taped to your thigh.
  • Less often, the external sphincter may be evaluated using needle electrodes inserted through the skin (this causes only mild discomfort) or an anal plug electrode.
  • A catheter is gently inserted through your urethra and into your bladder.
  • Electrical activity is recorded while you are relaxed and your bladder is empty.
  • For additional measurements, you may be asked to cough; the examiner may gently tug on the catheter; and you may be asked to contract and relax the sphincter muscles so that voluntary activity can be assessed.
  • Next, your bladder is filled with room-temperature water, the catheter is removed, and you will be asked to urinate.
  • The electrodes are then removed, and the affected area is cleaned and dried.
  • The test usually takes 30 to 60 minutes.

Video urodynamic studies:

  • The test is usually performed while you are seated or standing.
  • Cystometry is conducted as described above, with the only difference being that a radiographic contrast agent serves as the filling medium and fluoroscopy is used to produce an image of the lower urinary tract.
  • The pressure and volume measurements recorded in cystometry are displayed simultaneously with fluoroscopic images of the lower urinary tract on a TV monitor. The data can also be stored on videotape for later review.
  • To reduce radiation exposure, the total amount of fluoroscopic screening time is less than 20 seconds.
  • The procedure takes about 20 to 40 minutes.

Risks and Complications of Urodynamic Testing

Uroflowmetry:

  • There are no risks associated with this test.

Cystometry, urethral pressure profile, pressure-flow studies, electromyographic studies:

  • Temporary mild irritation of the urethra is common. Other possible risks include infection.

Video urodynamic studies:

  • Temporary, mild irritation of the urethra is common after this test. Other possible risks include infection.
  • The test involves minimal radiation exposure.
  • Rarely, some people may experience an allergic reaction to the iodine-based contrast dye, which can cause symptoms such as nausea, sneezing, vomiting, hives, and occasionally a life-threatening response called anaphylactic shock. Emergency medications and equipment are kept readily available.

After the Urodynamic Testing

All tests:

  • Resume your normal diet and any medications that were withheld before the test, according to your doctor’s instructions.

Uroflowmetry:

  • You may return home immediately.

Cystometry, urethral pressure profile, pressureflow studies, electromyographic studies, video urodynamic studies:

  • To relieve any post-test discomfort, your doctor may recommend a therapeutic bath in which you sit with your hips and buttocks immersed in warm, sometimes medicated water (sitz bath).
  • Drink plenty of fluids to relieve any burning on urination that may occur after the test.
  • In some cases, prophylactic antibiotics may be prescribed to prevent infection. Tell your doctor if you experience any symptoms of infection, such as pain, fever and chills.
  • If needle electrodes were used for electromyographic studies, blood may collect and clot under the skin (hematoma) at the needle insertion sites; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.

Results of Urodynamic Testing

  • A physician will review the data from the various urodynamic studies to determine what type of urinary dysfunction is present.
  • If a definitive diagnosis can be made, appropriate therapy will be started.
  • Additional tests, such as cystography and cystoscopy, may be needed to further evaluate any abnormal findings and establish a diagnosis.

Source:

The Johns Hopkins Consumer Guide to Medical Tests

Simeon Margolis, M.D., Ph.D., Medical Editor

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 25 Jan 2012

Last Modified: 04 Jun 2014