Urodynamics / Urodynamic Study


Urodynamic study (or urodynamics) is a study that assesses how the bladder, urethral sphincters and urethra are performing on storing and releasing urine. It is a group of diagnostic procedures performed to evaluate voiding disorders, and this also includes the assessment of the lower & upper urinary tract anatomy and its hydrodynamic functions. It is indicated when there is a voiding problem (problems with urination) which is unexplained or requires further assessment to evaluate bladder and urethral sphincter function.

One needs to have a very broad understanding of urology, different phases of filling and voiding, urinary dysfunctions and hydrodynamics of urine flow.

Urodynamic procedures in general evaluate function of the lower urinary tract (although the Whitaker’s test assesses the upper tract). Hence understanding urodynamics begins with understanding lower urinary tract anatomy and physiology.

There are 2 basic aims in proceeding with Urodynamics:

  1. It is essential to reproduce the patient’s symptomatic complaints
  2. To subsequently provide pathophysiological explanations of the patient`s problems


The various types of Urodynamic studies include:

  • Uroflowmetry
  • “Eyeball“ urodynamics
  • Sphincter EMG assessment
  • Single channel electronic cystometrogram
  • Urethral pressure profilometry
  • Cystometrogram with abdominal pressure measurement
  • Detrusor pressure/uroflow studies – Pressure flow studies
  • Multichannel studies (cystometry,abd pressure,uroflow,urethral pressure, sphincter EMG)
  • Video-urodynamics (multichannel urodynamics & fluoroscopy of LUT)
  • Voiding cystourethrogram (when video-urodynamics unavailable)

When is the Urodynamic study done

Urodynamic studies are done for various lower urinary tract symptoms, including the evaluation of incontinence (leaking of urine), overactive bladder symptoms, and urinary retention.

The purpose of the urodynamic study is to evaluate bladder function and its relationship to the urethral sphincter in difficult to diagnose cases especially those prior to therapeutic approaches, including prior to medical treatment, and in particular before surgical interventions.

Urodynamics is done to guide initial treatment, to follow progress with treatment or to evaluate treatment failures.

In patients with neurogenic bladder/sphincter dysfunction, urodynamics are often obtained to evaluate the risk for upper urinary tract damage in those with bladder/sphincter dysfunction.

The basic assessment before Urodynamic study include:

  • A thorough history
  • Physical examination and focal neurological examination, pelvic examination in females and prostate examination in males
  • Urinalysis, microscopy and culture
  • KUB X-ray if necessary
  • Ultrasonography KUB if necessary
  • Pad test – 1H pad test/ Ambulatory pad tests
  • Voiding diary
  • Free uroflowmetry and post-void residual urine (USG)
  • Urine analysis & culture
  • Upper urinary tract evaluation (optional)
  • Cystourethroscopy (optional)

During physical examination, the urologist will assess the neurological status, the pelvic floor, prostate examination and assess for any urine leak on coughing (stress incontinence).

A frequency volume chart or a voiding chart is usually required prior to proceeding with a urodynamic study. This is to assess the type of urinary problem one is suffering from, and to have a good idea of the bladder capacity before the urodynamic proper.

The frequency volume chart or voiding diary consists of noting down how much and how frequent one passes urine and to note this into the diary. The oral fluid intake and any urgency and urinary leak is also charted down into the diary.

Also a proper assessment of the various symptoms will be made by the doctor, using various assessment charts or just a detailed history.

Before the urodynamic study, the patient will be advised to prepare for the study by ensuring the bowels are clear.

On the day of the urodynamics, a brief description of the procedure will be explained by the urologist.

Then a preliminary simple study consisting of uroflowmetry and ultrasound of the bladder before and after your pass urine, including the kidneys. This is to detect and assess the urinary flow, any residual urine in the bladder after passing urine and the extent of severity of flow prior to the more detailed urodynamic study.

The patient will be made to pass urine in privacy into a uroflowmetry machine and the flow rate and pattern is recorded, so as to have a good idea of the urinary problem prior to the urodynamic study.

The uroflow patterns can be noted by a continuous tracing which is recorded when the urine flows along the uroflowmetry machine. The urologist can determine the provisional diagnosis after the uroflowmetry.

By using various flow rate nomograms, the urologist can determine whether the flow is normal or slow, and whether it may be obstructed or not.

Ultrasonography of the bladder before and after passing urine will be done to assess the amount of residual urine left back in the bladder.

This will assess the Bladder Voiding Efficiency.

The urodynamic study will then be conducted after the pre-assessment.

The urodynamic machine is a computerized machine connected to the uroflowmetry machine, and has pressure transducers connected to it for recording the various bladder and abdominal pressures.

The procedure consists of placing a small catheter through the urethra (urinary passage) into the bladder. Another small catheter is placed into the empty rectum (back passage).

Parameters measured during urodynamics are various pressures, urinary flow, the relationship between pressures during urinary flow, EMG sphincter assessment and occasionally video imaging to assess the function of the sphincter during filling and voiding as well as evaluation of any vesicoureteric reflux.


Urodynamic machine

Connected to a uroflowmetry machine

There are various other accessories and catheters that will be set up by the urologist for the urodynamic study.

There are times when an EMG recording is required to see the functioning of the urethral muscles. This is done by placing 3 stickers (surface electrodes) on your behind, which will measure the contraction of your urethral and back passage muscles.

Typical Urodynamic Tracings

The urodynamic study consists of 2 phases:

  1. The filling phase, where saline will slowly be infused into your bladder
  2. The voiding phase, where you will pass urine into the uroflowmeter when your bladder is full.

During the filling phase:

After calibrating the instrument and setting up, some saline will be infused through the catheter into the bladder.

You will be instructed to inform the urologist of the various sensations you will feel while the bladder is being filled with normal saline. The various sensations that need to be recorded are the first desire to void (pass urine), normal desire to void, strong desire to void and urgency.

Any leakages of urine during the procedure while filling up the bladder will be recorded by the urologist.

Various types of urinary leakages (incontinence) will be identified during this procedure.

The pressures during the filling phase is recorded to determine if you have a stable bladder, whether the bladder is too active or whether the bladder is weak. At the same time, the type of urinary leakage (incontinence) is determine by assessing the leak and the pressures seen during leakage.

The above tracing shows an unstable bladder

During the voiding phase:

Thereafter, you will be instructed to pass urine into the flow rate container, in what is known as the voiding phase of the urodynamic study. The flow and the related pressures through the catheter will be recorded.

The various pressure tracings are recorded and will be explained to you.

The above is the typical Urodynamic tracing.

Below is the typical voiding phase of Urodynamics.

The pressure flow analysis is done to determine if you have a weak bladder or an obstructed bladder after the voiding phase of urodynamic study.

This can then be plotted on a pressure flow plot to determine if one has an obstructed bladder, weak bladder or a normal bladder.

Using the Pressure-Flow Study and the p-Q plot, your urologist will be able to determine if you have an obstruction or a weak bladder.

Your urologist will explain the findings to you, as well as the final urodynamic diagnosis.

Interpretation of various urodynamic tracings

What is Urethral pressure profilometry (UPP)?

Urethral pressure profilometry (known as UPP) is another type of urodynamic study that may be combined together with the main urodynamic study.

It is a study for which the topographic curve plots the urethral closure pressure (UCP) along the length of the urethra. It is usually done before the main study.

Your urologist can explain to you about this.


To perform UPP, a measurement catheter is pulled slowly, by a defined distance/time through the urethra thus obtaining a pressure profile along the inside of the urethra.

Four catheter types are common in clinical use today: water-filled infused catheters, water-filled latex balloons, air-charged balloon catheters, and microtip catheters; with each type possessing certain advantages and disadvantages compared to the others.

The Urethral Profilometry procedure is done with the same settings during Urodynamics, and is done just before the filling phase of the Urodynamic study

Stress UPP

Stress UPP on the other hand is measured by getting the patient to repeatedly cough while measurement catheter is pulled slowly, by a defined distance/time through the urethra thus obtaining a pressure profile along the inside of the urethra during coughing. 

By analyzing the tracings of the UPP, your urologist will have a good idea on the relationship of your urethra during bladder filling and during coughing, and have an idea of your urine leakage, and whether it is due to a weakness of your urethral sphincters or not .


What is videourodynamics?

Videourodynamics is urodynamic study done with fluoroscopic imaging techniques. There are some conditions where continuous imaging is required, especially assessing the bladder neck and visualizing any urine refluxing back into the ureters.

Your urologist can explain to you about this procedure.


The following are Video-urodynamic images and tracings

In summary

Urodynamic study is essential for certain cases of urinary problems where it is difficult to determine if it is due to obstruction or a weak bladder, as well as conditions where there is incontinence (leaking of urine) to differentiate the type of urinary leakage so as to aid in the proper treatment of the disease.

When to see the urologist

When referred by the primary doctor, urologist or gynecologist for difficult to diagnose urinary problems, as well as to aid in treatment of urinary diseases.

You may feel uncomfortable to discuss incontinence and various other embarrassing urinary problems with your doctor. But if the incontinence or other embarrassing urinary problems is frequent, bothersome or is affecting your quality of life, it’s important to seek medical advice because urinary incontinence may be caused due to a more serious underlying condition, can restrict your activities and limit your social interactions, can be embarrassing while interacting with your family members and friends, and increases the risk of falls in older adults as they rush to the toilet to pass urine.