The Difference Between Urodynamics and Cystometrogram (CMG)

Posted by Clark Love on Jul 30, 2021 5:29:29 PM

KidneysUreterAndBladderWhen it comes to conditions of the lower urinary tract, there are key differences to consider in order to determine which form of testing is the most appropriate. While there are striking similarities between methods that can potentially create confusion upon first glance, a practitioner knows which test is most appropriate for the corresponding symptoms.

One area that has the potential to create this confusion is determining the difference between the need for the broader Urodynamics testing panel or the Cystometrogram. While these two procedures involve many of the same elements, they are in fact different.

This post will provide a detailed comparison of the two methods and describe how they are similar, but also different. First, a brief explanation of the two methods before we compare:

Urodynamics: A Complete Panel of Urology Tests

Urodynamics is the term for the all-encompassing series of tests and procedures regarding the lower urinary tract (bladder and urethra). It is generally performed as an outpatient procedure performed within a urology, gynecology, or urogynecology practice.  It is typically performed by a pelvic health specialist nurse.  

The range of tests performed under the scope of Urodynamics include:

  • Cystometrogram — testing bladder function, pressure and volume
  • Electromyography — recording of electrical activity within muscle tissue
  • Urethral Pressure Profile — measuring the balance of pressure along the urethra
  • Uroflowmetry — testing the volume of urine released from the body
  • Pressure Flow Study — measuring the bladder pressure required to urinate and the generated flow rate

These tests are commonly performed upon the onset of certain symptoms that indicate lower urinary tract distress, such as incontinence, urgency to urinate, frequent urination, and weak urine flow, to name a few examples.

While it is possible for a provider to recommend one or more of these tests individually based on symptoms, Urodynamics is most often performed as a complete series of tests.

This is the most thorough method, and the best way to determine what may be the cause of — and therefore the best treatment method for — the lower urinary tract symptoms a patient is experiencing.


Cystometrogram: A Single Purpose Test

A Cystometrogram is a test that works to determine the cause of symptoms patients may be experiencing in relation to the filling and emptying of the bladder. Symptoms may include issues such as incontinence or urine retention, for example.

The Cystometrogram measures the volume of urine a patient’s bladder can hold, how full the bladder is when the patient feels the urge to urinate, and the pressure of the flow of urine.

The test is performed by emptying the bladder completely by way of a catheter, then filling it back up again with warm, sterile water. The patient then communicates with the provider upon specific sensations, for example the urge to urinate and the accompanying intensity.

Each time the patient experiences a new sensation (or different intensity of a sensation), the volume of water in the bladder is measured, as well as the degree of pressure inside the bladder. Tests may be performed to check for leakage or involuntary muscle contractions during this time as well.

This entire procedure serves as a recreation of events; a means of discovering what may be causing the patient’s symptoms. By recreating the process of filling and emptying the bladder in a controlled setting, the provider can determine not only what may be the cause of the symptoms, but the best method of treatment for the individual patient.


Urodynamics and Cystometrogram: A Comparison

When attempting to compare the Cystometrogram to Urodynamics, the major differences are clear. By simply reading this far it may have occurred that the Cystometrogram is an element of the Urodynamics test sequence, although it is of course available as a stand-alone test as well.

For issues pertaining solely to the filling and emptying of the bladder such as incontinence or urine retention, the Cystometrogram may be the most practical route based on what the patient is presenting.

The practitioner can always order the full Urodynamics as a follow up, however if there is any question of the need for Urodynamics it is likely the practitioner will perform it. This makes sense for the sake of patient comfort and practitioner availability, as well as insurance purposes.

For any lower urinary tract symptoms, including those discussed above, the Urodynamics testing sequence is the most thorough method, and in fact the only method that serves to illuminate any and all possible disorders of the region.

The high level of involvement and accuracy provided by Urodynamics is the very reason practitioners perform it; the results speak for themselves.

While it is possible to compare Urodynamics and the Cystometrogram, the two so regularly go hand in hand that it doesn’t often seem necessary to put one in front of the other.

However, when it comes to accuracy, uncovering any possible causes of discomfort, and being as thorough as possible with patients, the obvious choice is to go for the full Urodynamics panel.



For patients with lower urinary tract issues, time is of the essence. It is highly likely that they are feeling uncomfortable, worried, and in need of treatment options so that they may begin to feel some relief. In the case of determining whether to perform a Cystometrogram or Urodynamics, more is usually better.

However, if the patient is exhibiting very specific symptoms, the provider then of course has the discretion to perform the Cystometrogram if they see fit to do so.

Urodynamics is highly effective in determining, and in some cases, preventing, the cause of lower urinary tract distress. When testing is performed appropriately, the possibility of promoting a better quality of health is possible for the patients, when a practitioner is able to identify the problem in its early stages.

While the Cystometrogram certainly has its place and is a vital tool in the lower urinary tract health field, the option to identify as much information as possible is available in just one patient visit when choosing to perform Urodynamics. These two methods go hand in hand, yes. But one surpasses the other in terms of discovery, and that would be the all-inclusive Urodynamics panel.

If you are a physician or part of a practice that would like to offer urodynamics, then please consider Brighter Health Network (BHN) for your urodynamics needs. BHN offers turn-key urodynamics testing (which includes the staff, equipment, supplies, software, and a compiled report for each patient) and urodynamics staffing.


Get Urodynamics Testing Services Details + Pricing Now

Topics: Urodynamics Testing, BHN, outsourcing diagnostics, urodynamics, incontinence, urodynamics service provider, male urodynamics, stress incontinence, Uroflow, Uroflowmetry, UroGynecology, Cystometrogram

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