Urodynamic Studies

Urodynamic Studies | Pacific Urology | photo of urologist talking with male patient

Urodynamic studies test how effectively the lower urinary tract (bladder, bladder opening and urethra) holds urine, stores it and then releases it. Such tests give urologists a better understanding of the pressure and flow relationship of these organs and aid in diagnosing the cause of urinary problems in men or women.

Patients may be in need of urodynamic studies if:

  • They involuntarily release urine on a routine basis (incontinence)
  • They are unable to voluntarily void urine (urinary retention)
  • They have incontinence that has no apparent cause
  • They have frequent urinary tract infections (UTIs)
  • Urination is painful, frequent or comes on suddenly
  • They have difficulty starting urination or completely emptying the bladder
  • The urologist suspects there is more than one cause of incontinence.

Additionally, the urodynamic evaluation can be helpful in determining the underlying cause of overactive bladder (OAB), such as diabetes, neurological disorders and abnormalities in the bladder.

Urodynamic studies can be noninvasive observations and measurements performed in a doctor’s office. The tests may be simple, but increase in complexity according to the nature and extent of the diagnosis.

Urologists discuss the appropriate urodynamic testing options with each patient, depending on his or her specific situation and the results of previous test results. A combination of urodynamic studies may be needed to fully evaluate urologic problems. These tests are often performed at the same time and typically take about two hours.

Kinds of urodynamic studies

Urodynamic tests evaluate the three parts of the lower urinary tract: The bladder, the sphincters and the urethra tube. These studies check the filling and storage phase of the bladder and the voiding (expelling) stage of urination that involves the bladder, sphincter muscles and urethra.

Most urodynamic studies evaluate the bladder, as that is where urologists generally find the problem. Sometimes urologists can conduct urodynamic studies designed to recreate a patient’s symptoms and urinary response.

The patient will be well informed about what to expect and how long the evaluation may take. Patients are generally advised to arrive for their evaluation with a comfortably full bladder.

If a patient is on a bladder relaxation medication, he or she usually will need to stop taking that medication five days before the test. Women who think they might be pregnant should also notify the office before scheduling a urodynamic study.

The various types of urodynamic studies follow.


In this study, a computer records data that measures the speed of urine flow and the volume. The patient in a screened off area urinates into a special device that measures the speed of the urine flow, how it fluctuates and when the flow rate is highest. These measurements can indicate weak bladder muscles or a blockage restricting urine flow. The study is performed in the urologist’s office with no need for anesthesia.


This test evaluates the bladder’s function, measuring how much urine it holds, how much pressure forms as the bladder fills with urine, and how much urine is in the bladder when the patient begins to have an urge to urinate. The patient is given local anesthesia, the bladder is emptied using a catheter, and a small catheter with a pressure measuring device called a manometer is inserted into the bladder.

The bladder is filled with sterile water and the patient is asked to indicate when he or she begins to feel the need to urinate. At that time, the volume of water and the pressure inside the bladder are recorded. The patient may also be asked to cough or strain during the bladder filling to see if the manometer detects a change in pressure.

Leak point pressure measurement

This test is done during cystometry and records the pressure in the bladder when it involuntarily contracts and expels fluid. To evaluate the sphincter muscles used during leakage, the urologist will have the patient apply pressure to the bladder by coughing, changing position or other means. The leak point pressure measurement gives the urologist information on the specific nature of the bladder problem.

Pressure flow test

After cystometry is performed, a pressure flow study may be done to measure the bladder pressure needed for a patient to urinate and to record the flow rate of urine at different pressures. It is mostly used in males to evaluate the bladder blockage caused by an enlarged prostate. It may also be used on women who previously have had surgery for urinary incontinence or who have a cystocele, which occurs when the bladder droops into the vagina.

Postvoid residual measurement

The urine left in the bladder after urination is called postvoid residual. A measurement of 100 milliliters or more of urine postvoid indicates the bladder is not completely emptying. This urodynamic study can be done with ultrasound images. It can also be done by inserting a catheter to collect and measure the residual urine.


This test assesses nerve or muscle issues in the bladder and sphincters the urologist thinks may be contributing to urination problems. Sensors record the muscle and nerve activity patterns and can show if the messages sent to the sphincters and the bladder are abnormal. The sensors are placed on the skin in these areas, requiring no anesthesia.

Video urodynamic test

This advanced urodynamic study takes video or still images of the bladder while it fills and empties. These images clearly show the shape of the bladder and its size, which helps the urologist evaluate the urination problems. Ultrasound or x-rays may be used to produce the images. If ultrasound is used, the patient’s bladder will be filled with a special fluid that helps provide a better picture of the bladder.

Risks and considerations of urodynamic studies

There is a small risk of infection after this type of procedure. If an infection occurs, the urologist will prescribe an antibiotic. Sometimes an antibiotic may be prescribed as a precaution.

If new symptoms of burning, urinary frequency or bleeding occur afterwards, patients should notify the clinic. Discomfort may occur when urinating for a few hours after the testing. Drinking water can help with this, as can taking a warm bath.

How the lower urinary tract works

In the lower urinary tract, the bladder is located in the pelvis and receives urine from the kidneys that have filtered excess water and body waste to create urine. The bladder swells larger when full of urine and shrinks when expelling urine via the urethra. This action involves the sphincter muscles surrounding the bladder where it opens to the urethra tube.

The lower urinary tract works efficiently when the muscles and nerves are coordinated to do their jobs efficiently. A normal urinary tract can hold about 2 cups of urine comfortably for about 2-5 hours, depending on the individual.

Learn more about the urinary system