What is Urodynamic Testing?

Introduction

 

Urodynamic testing is the gold standard for evaluating lower urinary tract dysfunction (LUTD). The invasive and intimate nature of the procedures can cause patients to experience emotional and physical discomfort. Lack of privacy can lead to embarrassment and inability to void. The bladder filling with catheters has an increased filling rate compared to the natural physiological filling of the bladder causing variable diagnostic accuracy. Individualized pre-testing education can diminish emotional and physical discomfort. There is a small risk of catheter complications such as gross hematuria with an enlarged prostate and urinary tract infection. Ambulatory urodynamic monitoring measures bladder pressure over an extended period of time with a portable monitor and indwelling bladder and rectal catheters. The drawback to the ambulatory monitor is it is unable to measure bladder volume.

 

Traditional Urodynamic Studies

 

Uroflowmetry: Uroflowmetry is a non-invasive test to evaluate how well the lower urinary tract functions, indicates weakness in bladder muscles, and if there are any obstructions with urine flow. It measures how much urine is in the bladder and the rate of time required to empty the bladder. The patient urinates into a toilet that has the appearance of a bedside commode with a funnel and a scale. The patient is asked to urinate when they feel their normal desire to void. The test is conducted in the patient normal voiding position (sitting or standing). The device creates a graph that shows changes in the flow rate during urination. 

 

Postvoid Residual Measurement: This test can be performed by catheterization or by ultrasound to measure the remaining urine after voiding. The bladder is not emptying properly if there are 100-150 milliliters of urine or more left in the bladder. Insertion of the catheter can cause discomfort and embarrassment.

 

Cystometry: Cystometry test measures the amount of urine a patient can hold, how much pressure builds up in the bladder during the storage phase, and the amount of urine in the bladder when a patient starts to feel the urge to urinate. The test can also detect bladder contractions. There are two catheters placed in the bladder. One catheter is placed in the bladder to completely empty it, and the other is a manometer. The manometer catheter fills the bladder with warm water and records pressures in the bladder. Another catheter may be placed in the vagina or rectum for recording pressure measurements in that location. 

  • Leak point pressure measurement: This test evaluates the sphincters and can indicate the type of bladder problem. The patient may be asked to cough, Valsalva Maneuver, or shift position. A cystometry test also identifies if the bladder is contracting when it is not supposed to and suddenly contracts and leaks water out without warning while the bladder is filled with water. The pressure is measured inside the bladder when the leakage occurs and measures the leak point pressure. 
  • Pressure flow study: This study can indicate bladder outlet blockages such as prostate enlargement or pelvic organ prolapse. The pressure-flow study measures how much bladder pressure is needed to urinate and how quickly the urine flows at that pressure. 

 

Electromyography: This test is conducted if the urinary problem is related to nerve or muscle damage. The electromyography machine records muscle and nerve activity with the use of sensors placed on the skin near the urethra and rectum. If there is a urethral and rectal catheter is placed, the sensors will be on the catheters. The sensors measure the electrical activity of the nerves and muscles around the bladder and sphincter. This test will show nerve impulses and if the bladder and pelvic floor muscles are coordinating correctly.

 

Video Urodynamic Testing: Video urodynamic tests use radiologic fluoroscopy imaging and videos of the bladder while it fills and empties. A catheter is inserted and fills the bladder with contrast fluid. The test is conducted in a sitting position with a radiolucent toilet seat or in a standing position. Patients with neurological dysfunction or unable to sit or stand can perform the test in a supine position. 

 

Ambulatory Urodynamic Monitoring (AUM): This monitoring system has a portable monitor connected to the indwelling bladder and rectal catheters. The device monitors bladder pressures during the patient’s physiological filling and voiding and is monitored over a longer time than the traditional urodynamic study. The indwelling catheters can produce artifacts. The battery device is non-chargeable and lasts between 24 and 36 hours. This device does not measure or control bladder volume. Instead, the testing is supplemented with an ultrasound-based system to measure the bladder volume before inserting the catheters. Body-worn briefs with a monitor or an event button on the monitor to monitor leaks.

  • Telemetric wireless, catheter-free, portable monitoring devices are under current development and some reached the testing phase of research. Some devices offer capabilities including bladder volume measurement.

 

Conclusion

 

Urodynamic testing is the current standard for evaluating LUTD. The results can provide informed explanations to patients regarding the causes of their symptoms and guide the treatment plan. However, traditional testing has significant limitations, such as adverse effects and issues with data reproducibility. AUM was developed to address some of the limitations of traditional testing. However, it uses catheters and does not measure or control bladder volume. Telemetric technology has excellent potential for improvement of monitoring without adverse effects or complications.

Disclaimer

The views and opinions stated in this blog are exclusively those of the author and do not reflect iWound, its affiliates, or partner companies.

References

 

Abelson, B., Majerus, S., Sun, D., Gill, B. C., Versi, E., & Damaser, M. S. (2019). Ambulatory urodynamic monitoring: state of the art and future directions. Nature reviews. Urology, 16(5), 291–301. https://doi.org/10.1038/s41585-019-0175-5

 

Drake MJ, Doumouchtsis SK, Hashim H, Gammie A. Fundamentals of urodynamic practice, based on International Continence Society good urodynamic practices recommendations. Neurourol Urodyn. 2018 Aug;37(S6):S50-S60. doi: 10.1002/nau.23773. PMID: 30614058.

 

Gammie A, Drake MJ. The fundamentals of uroflowmetry practice, based on International Continence Society good urodynamic practices recommendations. Neurourol Urodyn. 2018 Aug;37(S6):S44-S49. doi: 10.1002/nau.23777. PMID: 30614059.

 

Wyndaele M, Rosier PFWM. Basics of videourodynamics for adult patients with lower urinary tract dysfunction. Neurourol Urodyn. 2018 Aug;37(S6):S61-S66. doi: 10.1002/nau.23778. PMID: 30614055.

 

Yang, T. H., Chuang, F. C., & Kuo, H. C. (2018). Urodynamic characteristics of detrusor underactivity in women with voiding dysfunction. PloS one, 13(6), e0198764. https://doi.org/10.1371/journal.pone.0198764

 

Yao M, Simoes A. Urodynamic Testing and Interpretation. 2021 Aug 11. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 32965981.

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