Hypothesis / aims of study
Pelvic floor muscle training (PFMT) is recommended as the first choice of conservative therapy for urinary incontinence (UI) following radical prostatectomy (RP). However, there are only a few facilities where physical therapists (PT) provide a detailed evaluation of pelvic floor muscle (PFM) movements when providing PFMT training guidance.
In 2022, an novel method to quantify pelvic floor function using M-mode ultrasonography (US) was applied to assess the effects of PFMT guidance in patients with UI after RP [1]. Therefore, the purpose of the present study was to quantify the aforementioned pelvic floor function and to clarify the changes in pelvic floor function due to PFMT guidance in patients with UI after RP, in addition to the relationship between pelvic floor function and the degree of UI.
Study design, materials and methods
This study was approved by the ethics review board of our hospital, and informed consent was obtained from the patients. The study included 58 patients (mean age: 70.7 ± 7 years) with UI following RP who received regular PFMT instruction by an experienced PT for at least 3 months (or until UI = 0 g/day) and were able to continue recording their urinary diaries at home.
Pelvic floor function was measured using transabdominal ultrasonic tomography, which visualized the bladder in a state of urine storage in the midsagittal plane and an M-mode cursor was placed on the part of the bladder that moved the most during PFM contraction. Pelvic floor function evaluation with M-mode US measurements was performed three times from the starting point of bladder base elevation to the maximum elevation point during PFM contraction. The bladder base elevation time (s) and bladder base elevation speed (mm/s) were quantified (average value of three measurements). The UI volume (g) was measured at each pad change and recorded in a micturition diary.
The frequency of PFMT instruction by the PT was 5–8 times in the first month of intervention, concentrating on learning the PFMT method. After the first month of intervention, the instructional intervention continued approximately once every 1–2 months depending on the motor acquisition status. The PFMT taught by the PT consisted of a program that approached all aspects of the trunk, pelvic floor, and hip function.
Changes in pelvic floor function with PFMT instructions were compared in terms of the bladder base elevation time and bladder base elevation speed during PFM contractions during and after continued PFMT. The relationship between pelvic floor function and UI volume was evaluated by the correlation between the bladder base elevation time and speed of bladder base elevation, and the volume of UI during the intervention and after the continuation of PFMT.
The Wilcoxon signed-rank test was used to measure changes in UI and pelvic floor function due to PFMT, and Spearman's correlation coefficient was used to measure the relationship between UI and pelvic floor function. The statistical significance level was set at P<0.05. All statistical analyses were performed using IBM SPSS 29.0 software (IBM, Armonk, NY, USA).
Results
The average period of PFMT instruction for the 58 patients after RP was 9.3 ± 8.7 months, including 24 patients who underwent the intervention for >1 year after RP (average 40.1 ± 22.8 months), and two patients who underwent unilateral nerve-sparing surgery.
With continued PFMT, the bladder base elevation time was significantly shortened from 0.37 ± 0.19 s to 0.21 ± 0.05 s (P<0.001), and the bladder base elevation speed increased from 18.9 ± 10.9 mm/s to 33 ± 17.4 mm/s (P<0.001) (Fig. 1). The bladder base elevation time of the 24 patients who acquired UI of 0 g/day was 0.18 ± 0.03 s, which was shorter than the overall average value. Furthermore, the bladder base elevation speed was 34.6 ± 16.2 mm/s, which was faster than the overall average speed.
At the time of the intervention, the correlation between the volume of UI and pelvic floor function was assessed. A weak positive correlation was observed between the volume of UI and the bladder base elevation time (R = 0.323; P = 0.013), with no correlation observed with the bladder base elevation speed (R = –0.109; P = 0.412). After the continuation of PFMT (average 9.3 ± 8.7 months of instruction), the correlation between the volume of UI and pelvic floor function showed a positive correlation of UI volume with the bladder base elevation time (R = 0.524; P<0.001), but no correlation with bladder base elevation speed (R = –0.069; P = 0.604) (Fig. 2).
The average volume of UI at the time of intervention was 430 ± 474 g, which significantly decreased to an average of 151 ± 241 g (P<0.001) after PFMT instruction.
Interpretation of results
When a PT appropriately provides PFMT guidance to patients with UI after RP and the patient continues PFMT, the bladder base elevation time can be significantly shortened, and the bladder base elevation speed significantly increased. These results revealed that PFMT changes the pelvic floor function in patients with UI after RP.
In patients who achieved UI of 0 g/day, the bladder base elevation time was 0.18 ± 0.03 s, and the speed was 34.6 ± 16.2 mm/s. From Figure 2, focusing on the 24 patients who achieved UI of 0 g/day, there were characteristics in which the bladder base elevation time was less than 0.2 s and the speed was more than 20 mm/s. Therefore, the numerical targets for PFMT in patients with UI after RP are considered to be a bladder base elevation time of <0.2 s and a bladder base elevation speed of ≥20 mm/s, as in a previous study [1].
Furthermore, a weak positive correlation was found between the volume of UI and bladder base elevation time during the first intervention, and a positive correlation was found between the volume of UI and bladder base elevation time after PFMT. These results numerically demonstrate that pelvic floor function is related to UI volume.