This is the first study to investigate the relationships between urinary incontinence (UI) and pelvic floor muscle (PFM) function after robot-assisted laparoscopic radical prostatectomy (RARP) using a validated and quantitative PFM assessment tool. Pelvic floor muscle training (PFMT) for UI occurred after prostatectomy was recommended as Grade B in Incontinence 6th edition. In general, PFMT is consisted of a combination of instantaneous and sustained contractions. However, it remains unclear what PFMT program is effective for the patients after RARP. In this study, PFMT was performed on patients scheduled for RARP from 2 months preoperatively to postoperatively to determine the effect of PFM function on UI symptoms.

This study was designed as a randomized controlled trial (RCT). The subjects who were scheduled RARP were recruited in this study from 2017 to 2019. Exclusion criteria were serious psychiatric, neurological diseases, and/or lower urinary tract infection. Sample size was calculated based on the previous RCT that reported 24-hour pad weight at 3 months after radical prostatectomy as primary endpoint [1]. The sample size was set at 27 participants per group to provide a power of 80% and a significance level of 5% for detecting the difference between groups. A final sample size was set at 30, which considered 3 participants as dropouts in each group. We randomly assigned men to receive either supervised PFMT or control group. This study was approved by the Ethics Committee in our institution. All participants provided written informed consent prior to participation. The current study involves the utilization of existing data from our previous study, “The effect of supervised pelvic floor muscle training on pelvic floor muscle function for the patients with UI after robot-assisted laparoscopic radical prostatectomy - A Randomised Controlled Trial -” which was accepted in International Continence Society 2020. The primary endpoint determined 24-hour pad weight (g) at 3 months after RARP. Also, we defined urinary continence as no pad use in the present study. PFM function such as resting anorectal pressure, maximum anorectical squeeze pressure, endurance, average, gradient, and area under curve (AUC) were included. Regarding PFM function, a manometer with anal sensor (PeritronTM cat 9300A; Laborie, Canada) was utilized for quantitative PFM assessment [2]. Maximal anorectal squeeze pressure is the peak value of anorectal squeeze pressure during contraction of the PFM. Duration is measured when the pressure reaches above 5 cm H2O. Average means area under the curve of anorectal squeeze pressure divided by contraction duration. Gradient is the peak value of anorectal squeeze pressure divided by the time taken to reach the maximum. Area under curve is anorectal squeeze pressure sampled 10 times per second, and divided by 10, multiplied by duration time. These outcomes were assessed before RARP, 7 days, 1, 3, 6, 12 months after RARP. The subjects in supervised PFMT group attended one-to-one PFMT session 3 times preoperatively, plus 7 days, 1, 3, 6, 12 months after RARP in total 8 times. In each session, subjects in supervised group were provided one-to-one session with a physiotherapist. Supervised group received verbal information about pelvic floor anatomy and function using an anatomical male pelvic model. They were taught isolated contraction of PFM without contracting the other muscles, including the outer abdominal muscles, and muscles of the hip joint with verbal instruction and palpation of PFM. Home-based PFMT was performed throughout this study. The subjects in control group were given only a leaflet about PFMT and lifestyle advice as daily care in our hospital.
In order to clarify the factors affecting the presence or absence of UI in 12 months, logistic regression analysis (forced input method) was performed. The dependent variable was the presence or absence of UI in 12 months, and the independent variables included the presence or absence of PFMT, body mass index (BMI), age, maximum anorectical squeeze pressure, endurance, and AUC. The significance level was set at p<0.05.

A total of 50 subjects (the number of supervised PFMT group: 24, control group: 26; Age: median 72 years old, range 52 – 80 years old; BMI: median 23.1 kg/m2, range 16.8-31.9 kg/m2) were completed throughout this study. The urine loss on 24-hour pad weight was significantly lower in the supervised PFMT than in the control group at 3 months after RARP (p=0.02). The rate of continent patients in the supervised PFMT group (65.2%) was significantly higher than that in the control group (31.6%) at 12 months after RARP (p = 0.03). The results of PFM function at 7 days after RARP were shown in Table 1. The relationships between UI and PFM functions by analyzing the logistic regression analysis are shown in Table 2. The logistic regression model was adjusted for body mass index (BMI) and age. PFMT (odds ration = 0.084, 95% confidence interval (CI): 0.009 - 0.475, p = 0.01), endurance (odds ration = 0.952, 95% CI: 0.897 - 0.995, p = 0.04) and AUC (odds ration = 1.001, 95% CI: 1.000-1.001, p = 0.02) were factors affecting the presence or absence of UI at 12 months after RARP.

Our results showed that PFMT group significantly reduced in UI at 3 and 12 months after RARP compared with control group, which indicated that supervised PFMT could contribute to the improvement of postoperative UI. Supervised PFMT which consisted of visual inspection and palpation in a one-to-one session with a physiotherapist improved the PFM function. When PFM was contracted sufficiently, it can provide structural support in the pelvis to prevent urinary leakage during increased intra-abdominal pressure.
     While 24-hour pad test has been the objective measurement of UI, various UI definitions has been established, such as gram, pad number, questionnaires. The pad number is not a reliable measure of incontinence due to individual reasons, such as differing acceptable hygiene and pad wetness levels [3]. In this study, we defined UI as no pad use by using pad number in order to categorize the presence or absence of UI. Because this is thought to be the most distinct definition to measure actual urine loss in daily life in pad number.
     PFMT program generally targets PFM strength, power, endurance, and integration into activities, such as coughing and heavy lifting. However, it is unclear what parameters of PFM function contribute to the improvement of UI after RARP. Additionally, one of our strengths was that PFM function was evaluated with a method found to be good reliability in our previous study [2]. 
This study demonstrated that endurance of PFM contraction was independently associated with UI. It would be important that PFMT consists of the program to contract PFM longer for reducing postoperative UI. Moreover, PFM consists of approximately 70 % slow-twitch (type 1) and 30% fast-twitch (type 2) muscle fibers. Slow-twitch muscle fibers are characterized as muscles with long contraction duration, associated with endurance. PFMT focusing on how to maximize the ability to contract slow-twitch fibers of PFM can be effective to decrease UI.

The results of this study showed that PFMT had an important role in improving UI after RARP. Endurance of PFM contraction is independently associated with UI. This is the first study to reveal that endurance is an essential factor in the ability to prevent UI after RARP. The optimal PFMT program for the patients with UI after RARP should be considered.

Mariotti G et al. Early recovery of urinary continence after radical prostatectomy using early pelvic floor electrical stimulation and biofeedback associated treatment. J Urol. 2009;181(4):1788-93.
Ouchi M, Kitta T, Takahashi Y, Chiba H, Higuchi M, Togo M, Shinohara N. Reliability of manometry for assessing pelvic floor muscle function in healthy men. Neurourol Urodyn. 2020;39(5):1464-1471.
Cecile T. Pham, Manish I. Patel, Sean F. Mungovan: Pad Weight, Pad Number and Incontinence-Related Patient-Reported Outcome Measures After Radical Prostatectomy. Société Internationale d'Urologie Journal. 2022;3(3):124-130. DOI: https://doi.org/10.48083/10.48083/TIWQ1657

Continence 7S1 (2023) 101012
DOI: 10.1016/j.cont.2023.101012