What is Urodynamics?

Urodynamics (UDS) is a study of bladder function, meaning a study of how the bladder works. The bladder has two main functions: to store urineand to empty urine. UDS evaluates both of these components.

Why is Urodynamics Performed?

There are many reasons for an urodynamic study. Your doctor will recommend the test if she has a specific functional question regarding your symptoms. For example, in the woman who has very bothersome urinary frequency, urgency and straining to urinate after a procedure, the question may be, “Is the procedure obstructing her emptying?” Most commonly your doctor may use this test to evaluate: urinary leakage, urinary retention, obstructive symptoms, urinary frequency/urgency, or bladder function in a patient with multiple sclerosis, spinal cord injury, longstanding diabetes or other medical problems.

How Is Urodynamics Performed and What Should I Expect?

An urodynamic study usually begins by having the patient urinate above an uroflow meter (patients who sit to urinate can use a potty chair over the uroflow, while those who stand to urinate are asked to urinate in a funnel above the uroflow container). The uroflow measures the amount of urine emptied and the rate of the urine flow over time.

Next, a urethral catheter is placed into the bladder. It is a very small and flexible tube that is connected to a pressure transducer to measure the pressure in the bladder. A small flexible catheter with a small balloon on the end is inserted into the rectum. It too is connected to an outside pressure transducer to measure rectal pressure. Why do you need to know the rectal pressure when the study is on your bladder? Good question. The bladder pressure is affected by pressure due to the bladder muscle and outside abdominal pressure. By measuring this abdominal pressure via a rectal catheter, any pressure contribution from the abdomen can be subtracted in order to identify the pressure due to the bladder muscle itself.

Small adhesive patch electrodes are placed on either side of the patient’s anus to measure pelvic floor muscle activity and sphincter functions of these muscles. The urethral sphincter is the specialized muscle around the urethra that keeps us from leaking urine. Once catheters and EMG patches are placed, the patient is either positioned standing or sitting over the uroflow. The bladder is then filled with water through the bladder catheter and the pressures during filling are monitored. The patient is asked several questions about sensation. At periodic volumes, the filling is stopped and the patient is asked to cough and/or bear down. These activities are used to assess for leakage. The patient is filled until she has reached her capacity, meaning she is very full and cannot hold anymore. She is then asked to urinate. In most cases, she will be able to urinate right around the urethral catheter, and pressures will be monitored during urination.

What Will the Doctor be Looking For?

The doctor is using her expertise to tailor the study to answer her urodynamic question. She does this by looking at several aspects of filling and emptying. Things that are evaluated during urodynamics:

During Filling of the bladder:

1. Bladder sensation- Is it normal?

2. Capacity of bladder-How much does it hold?

3. Compliance-How well does it stretch?

4. Bladder overactivity- Are there any involuntary bladder spasms during filling?

5. Leakage- Is leakage present and is it due to weakness of the sphincter muscle, bladder spasm or both?

During Emptying of the bladder:

1. Contractility- Does the bladder generate a contraction strong enough to empty itself?

2. Flow- Is the flow steady and normal speed?

3. Residual Urine- Does the patient empty fully?

4. Pelvic floor activity- Does the pelvic floor relax like it should during emptying?

All the various parameters are examined and interpreted to provide as comprehensive an assessment of bladder function as can be made.

How Long Does Urodynamics Take?

The setup such as: catheter placement, connecting the transducer lines and setting up the machine may take 10 to 15 minutes. The urodynamic procedure itself may take 20 to 25 minutes.

Am I Sedated for Urodynamics?

No, patients are fully awake for good reason. The patient needs to be awake to tell us what she feels, to follow the doctor’s instructions, and to empty her bladder when it is time.

Will It Hurt?

Since the procedure requires a catheter, the patient may experience mild irritation from the urethral catheter. The catheters are small and flexible though, so irritation is minimal. Studies show urodynamics to be very well tolerated and less painful than expected by most patients undergoing the procedure.

What the Urodynamic Room Looks Like?


What does an Urodynamic Tracing Look like?

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