What Is Cystometry?

What should I expect if I have cystometry? In this article, we'll tell you all about this useful study for urinary incontinence.
What Is Cystometry?
Sandra Golfetto Miskiewicz

Written and verified by la médico Sandra Golfetto Miskiewicz.

Last update: 03 February, 2023

Urodynamic testing consists of a series of procedures that provide ways of determining the functioning of the lower urinary tract (bladder, urethra, and prostate in men). After studying the person’s medical history, the doctor evaluates the case and decides if the patient needs this type of testing, such as cystometry.

Common urodynamic studies are as follows:

  • Non-invasive: Uroflowmetry (UFM) and post-void residue measurement.
  • Invasive: Cystometry (study of the bladder filling phase), pressure-flow study (for the bladder emptying phase), urethral function test, videourodynamics, and sphincter electromyography.

What is cystometry?

Cystometry is a procedure that evaluates the functioning (both motor and sensory) of the bladder during the bladder filling or continence phase. It measures the relationship between the pressure and the volume of the bladder.

It is used in the following contexts:

  • Urinary incontinence
  • Urinary retention (with difficulty in urination).
  • To decide on a surgical conduct in a bladder operation.
  • To evaluate the evolution of people with neurological diseases (for example, multiple sclerosis).

Although its a method that provides quality information, it isn’t recommended in the following scenarios:

Studies for the bladder such as cystometry.
Studies on the human bladder involve some contraindications., especially if they’re invasive.

Preparation prior to cystometry

The person must make a voiding diary for 3 days that includes voiding frequency, volume in each void, and notes of any voiding urgencies or urinary incontinence that may occur.

The pad test is a useful method in cases of urinary incontinence, as it consists of measuring the weight of a diaper to calculate the volume of urine. This is reserved for when the incontinence doesn’t allow you to complete the voiding diary precisely.

What’s the procedure like?

Cystometry is an outpatient procedure, and is generally performed in a urology service. It lasts about 30 minutes and, although painless, it can be uncomfortable.

The usual steps are as follows:

  1. The doctor will explain what the test is like, the purpose,e, and how the patient can cooperate.
  2. You’ll need to undress and put on a surgical gown.
  3. You’ll be instructed to empty your bladder.
  4. You’ll be asked to lie on your back on the exam table.
  5. Subsequently, a thorough cleaning of the urethra area will be performed.
  6. A well-lubricated catheter (transurethral catheter) is gently inserted into the urethra to instill fluid into the bladder and record intravesical pressure and filling. The tube is connected to a device called a cystometer, which measures the volume it can hold and the pressure in the bladder.
  7. A tube is then placed rectally (or vaginally) to record intra-abdominal pressure.
  8. With these two catheters and transducers, the pressure exerted by the detrusor muscle is measured using a mathematical formula.
  9. With an infusion pump, a physiological solution is introduced into the bladder at a constant rate.
  10. The patient is asked to describe what they feel, and any discomfort or pain. You’ll be asked to tell them when you have the first urge to urinate and when the urge to urinate can’t be resisted.
  11. When the bladder is completely full, you’ll be told to cough or stand up and urinate.
  12. Cystometry ends when maximum cystometric capacity is reached and the order to urinate is given. When urinating, the flow-pressure study is performed for the bladder emptying phase.
  13. The intravesical catheter is then removed

All the information about the filling and emptying of the bladder is recorded in the software of the urodynamics equipment and the doctor will obtain a plot of the different pressures and volumes. Depending on the case, the doctor may also prescribe other tests, with ice water or with bbethanechol

What to expect after cystometry?

Burning when urinating and urinating more frequently for a day or two is usual and temporary. This improves with the intake of plenty of fluids.

If you have mild pain in the pelvic area, you can relieve this with home sitz baths.

Does the procedure entail any risks?

After cystometry, irritation of the urethra, bleeding, and infection may occur. However, urethral fistula and bladder rupture are rare.

The doctor should be consulted urgently in the patient experiences chills with fever, severe pelvic or abdominal pain, persistent bleeding or clots coming out of the urethra, as well as interruption of urination for more than 8 hours.

Interpretation of cystometry results

Filling cystometry measures 5 basic parameters that are explained below.

1. The sensation during bladder filling

The normal progression of sensations that can occur as the bladder fills is as follows:

  • First desire to urinate: between 150 and 200 cc, which is 50% of the maximum cystometric capacity.
  • Strong desire to urinate: between 350 and 400 cc and it’s the usual desire to urinate.
  • Urination urgency: occurs at 450-500 cc – this is the maximum cystometric capacity.

The sensation is increased if the first desire to urinate occurs with less than 100 cccsand limits the cystometric capacity to 250 cccs Reduced sensation is considered when the desire appears before full bladder filling.

Absent sensation is when bladder filling has already occurred and there’s no desire to urinate. Finally, nonspecific feeling refers to a feeling of fullness without any real filling of the bladder.

2. Bladder capacity

This is the bladder storage volume. It corresponds to the maximum cystometric capacity that’s normal at 500 cccs

In patients with altered bladder sensation, the moment when involuntary urination begins, such as detrusor hyperactivity, low bladder compliance, or sphincter incontinence is taken into account.

3. Bladder accommodation

Accommodation is the ratio of the detrusor pressure variation and its corresponding bladder volume, both at the beginning of bladder filling and at maximum cystometric capacity.

When the bladder is completely filled there should be little or no pressure change. The initial value of the detrusor pressure and the volume should be equal to 0. The normal increase is 1 centimeter of water for every 40 cccsof fill.

Among the causes of impaired bladder accommodation are neurological diseases that affect the urinary tract, radiation therapy, and urinary tract obstruction.

4. Detrusor activity

During the filling or storage phase, the bladder is relaxed and compliant, with no changes in detrusor pressure. When detrusor contractions occur in this filling phase it’s called involuntary detrusor activity and can be spontaneous or provoked.

Detrusor hyperactivity can be phasic or terminal (a single, involuntary contraction of the detrusor to cystometric capacity). Therefore, the diagnosis will be reported as normal activity detrusor, neurogenic, or idiopathic hyperactive detrusor.

Urinary incontinence.
The study aims to simulate, in certain patients, the natural filling of the bladder that cannot be retained in incontinence.

5. Urethral function

The urethra contracts during the storage phase and will be higher than the intravesical pressure, even if there’s an increase in intra-abdominal pressure. Urethral function can be measured in two ways:

  1. Maximum urethral closure pressure (MUCP)
  2. Abdominal pressure

In the case of stress bladder incontinence, the ALPP indicates which type of incontinence predominates; and whether it’s genuine (loss of urethral support) or due to the sphincteric deficit (DEI).

If the pressure is less than 60 centimeters of water it usually indicates IED. Between 60 and 90 is considered moderately suggestive of IED. A pressure greater than 90 cm is suggestive of loss of urethral support.

Other measurements that can be used include the following:

  • Detrusor escape point: in people with neurogenic disease.
  • Urethral pressure profile: in men with radical prostatectomy and neurological disease, and women with stress urinary incontinence.

A minimally invasive study

Cystometry is a simple, quick  procedure, but it provides extensive and important information for the diagnosis of neurogenic diseases that attack the bladder.

If you need to carry out a cytometry test, then ask all the questions you need before you have it. Health professionals will guide you on the precautions and considerations you need to take.

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