Cystometry: A Procedure For Bladder Function
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There have been times when my patients arrive at their appointment with results from a urodynamic test that their healthcare provider had them undergo. Even with their test results in hand, my patients do not understand what they are looking at. Many times, I am going over those results with my patients and explaining what the results even mean.
But what exactly are urodynamic tests? Urodynamics are a great tool to identify the underlying cause of voiding dysfunction because the machinery sees what your bladder is doing in real time. This allows your providers to select the most appropriate intervention based on your results.
One common procedure under the umbrella of urodynamic tests is cystometrogram (or cystometry). With this procedure, the bladder needs to be filled with the healthcare provider inserting a catheter to fill a bladder with a sterile solution. "Cystometry is the continuous measurement of the pressure/volume relationship of the bladder to assess sensations, detrusor activity, bladder capacity and bladder compliance" (Homma et al., n.d.).
Cystometrogram Procedure
The provider will have the patient empty their bladder as much as they can before the procedure. A catheter is inserted into the urethra until it reaches the bladder. Then fluid is inserted into the bladder.
During this time, the patient is asked about sensations while the bladder is getting filled. The healthcare team records at what volume of filling the patient feels: first sensation, second sensation, strong desire, and capacity. Urge rises and falls, and is supposed to be a gradual incline as the bladder fills. The first sensation is not a cue to use the bathroom. Cystometry lets the provider and the patient know at what point of bladder fill does the patient feel the urge to void.
"Are my results normal?"
I had to dig through the research to find any sort of normal values. The problem is that there really aren't any. "Borderline (cut-off) values of volume or pressure for the various sensation are at present undetermined" (Homma et al., n.d.). As well, there aren't any exact reference values for normal urodynamic capacity. This is due to the technique of the provider doing the tests. The numbers given under one provider may differ when the test is performed by a different provider.
But I did find some numbers.
Bladder actual capacity: 300-600ml in normal adults
Natural bladder filling speed: 1-2 ml/min
On the test result page, you may see:
Post Void Residual
Volume infused at FIRST SENSATION
Volume infused at SECOND SENSATION
Volume infused at STRONG DESIRE
Volume infused at CAPACITY
Volume at first contraction
Leak with cough, if yes when?
As a pelvic physical therapist, knowing that there aren't normal ranges for each of the categories, I look at the numbers broadly and how they relate to each other. Does volume infused at capacity match within the range of bladder actual capacity of 300 to 600ml? How close to the beginning of filling is the patient's strong desire, and is it really close to when the patient feels the first and second sensation? First contraction is usually a sign that the bladder is spasming and that increases the urge to void. Was that first contraction closer to first sensation or closer to strong desire?
There are ways to treat urge incontinence which helps patients go to the bathroom on a more normal bladder schedule instead of being beholden to their bladder.
Next:
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