Hypothesis / aims of study
n use since the 1970s, urethral profilometry (UPP—Urethral Pressure Profile) is one of several measurements utilized as part of a full urodynamic diagnosis. It does, however, have a number of limitations as a test in everyday clinical practice. One of these disadvantages is its low reproducibility. This limitation results from the use of traditional catheters, which measure urethral pressure only from one direction of the urethral circumference. The urethra is not a symmetrical, thick tube. The pressure at different points of its circumference differ significantly which results from the urethra and pelvic floor anatomy and function. Consecutive measurements perofermed one by one , due to muscles reaction , do not allow to obtain precise , global pressures picture.
The presented study allows for the assessment of urethral pressure (Pura) along the entire length of the urethra. Pressure readings are taken at the same time in four directions radially every 90° with simultaneous measurement of the intra-bladder pressure (Pves). Dedicated software allows to obtain easy to interpretation three dimensional and mobile scan of urethral pressures. In pilot study reproducibility of the method is very high.
Study design, materials and methods
The pilot study to present the method was performed in 2018. Second stage , with repeatibility assesment finished in 2021.
First , 25 women which presented in the clinic for the treatment of urinary incontinence or after previous pelvic floor repair surgery had the measurements performed to present the study technique. Afterwards group of 40 women with different LUTS had been randomised to two groups to asses the repeatibility of the method. First group had two measurements performed by one researcher to check the method repeatibility, and second group had the examination performed by two physicians to chek the intraoperator repeatibilty.
The examination was conducted according to the ICS standards.
Urethral pressure measurements: After micturition, a Foley catheter 12 or 14 Fr is used to empty the bladder of residual urine. Next, using the catheter, the bladder is filled with 200 mL of sterile water at room temperature or slightly warmer. In patients with reduced bladder capacity, the bladder is filled to the maximum volume, before it causes discomfort for the patient. After removal of the catheter, a cough test is performed to confirm the absence or presence of leakage of urine. While the patient is in a semi-sitting position, the catheter is inserted into the urethra to a depth guaranteeing that all the sensors are in the bladder. In order to confirm that the catheter has been accurately placed, a cough test is again performed. The auxiliary line on the catheter (indicating channel Pura1) should be directed ventrally. The catheter is then attached to a pulling mechanism, which is used to pull the catheter out. The speed of the catheter withdrawal in each case was 1 mm/s. The resting urethral profile is performed twice on each patient and the stress (dynamic) profile is performed once.
Special 5 channel catheter, quadruple capillary set and decicated software was used to perform the study.
Results
Differences in pressure readings depending on the position of the catheter measurement channel in classic profilometry can be significant—even more than 50%. Depending on the location of the measurements taken regarding individual channels, differences in the functional length of the urethra were also found, with the P3 channel being the most variable indicator. We found that negative urethral pressures can be found along the whole lenght of the urethra, and as long as it is present in only one measuring channel patients can still be asymptomatic.
As for repeatibility - measurement deviations in pressure assessment less than 5 cmH20 [<5% of full measurement range] are accepted as resulting from the device settings and are clinically negligible. Similarily, for lenght measurements, deviations <5mm , for area measurment deviations less than 15 J/m2 and vector volume less than 50000 cmH2O2*mm ale due to the device settings and are clinically insignificant and negligible. In the table below (Table 1) standard deviations and percentage differences between measurements are presented. Depending on the parameter considered, from 67% to 100% of the records differed in less than 5%.
Interpretation of results
Three-dimensional profilometry likely results in the elimination of testing errors due to changes in the position of the catheter in the measurement channel. By using three-dimensional profilometry, the dimensional distribution of pressure in the urethra can also be comprehensively assessed during a stress test. Three-dimensional pressure distribution images can be obtained using dedicated software, and these images do not require complicated analysis.
It is assumed that the deviations of the measurements values up to 5% are within the measurement error and are negligible. Repeatibility of the functional examinations, such as urethral profilometry is influenced by many factors, among which are the patients movements, muscles tonus changes, patients relaxation or tensity. Taking all this factors into account, variability of the measurement values in presented study, which is generally less than 5% three dimensional profilometry can be considered as a method with good repeatability.What is more, the three dimensional recontructions of pressures distribution are comparable and compatible
Concluding message
Three dimensional profilometry , as a method of intraurethral pressures assesment, requires technical difficulty, time, patient discomfort comparable with classical technique. At the same time allows to obtain much more data in a form easy for interpretation. What is more, the method seems to be repeatible and eas to learn.Three dimensional Urethral profilometry, as its classical eqivalent was invented, should stay rather a research tool, or a technique dedicated to a narrow group of patients with complex symptoms and pathologies, but is worth to be consideredas a usefurl clinical tool for complex diagnostics of the urethra.