Hypothesis / aims of study
In 2012, robot-assisted radical prostatectomy became available in Japan for prostate cancer and has since become widely performed. Retzius sparing robot-assisted radical prostatectomy (RS-RARP), a procedure for removing the prostate through the vesicorectal pouch, was reported by Galfano et al. in the European Urology journal in 2010 (1), and was introduced at our hospital in April 2020. While conventional robot-assisted radical prostatectomy was performed via an anterior bladder approach, recent reports suggest that RS-RARP, which uses a posterior bladder approach, is superior in terms of postoperative urinary continence. However, the factors predicting postoperative urinary incontinence in RS-RARP remain unclear, and there are no reports including factors related to voiding function from urodynamic studies or MRI. Additionally, the reason why preserving the Retzius space contributes to postoperative urinary continence is unknown. Therefore, this study will compare the progress of achieving urinary continence after RS-RARP surgery with the results of a pressure flow study (PFS) before surgery and 6 months after surgery to clarify what factors are involved in achieving urinary continence.
Study design, materials and methods
This study is a prospective observational study. The subjects were 40 patients who underwent RS-RARP at Nara Medical University Hospital between June 2020 and July 2025. Age, body mass index (BMI), PSA, clinical T stage, NCCN risk classification, prostate volume (PV), membranous urethral length (MUL), console time, whether or not nerve preservation is performed, whether or not lymph node dissection is performed, and number of pads used postoperatively were measured. Furthermore, the results of a PFS before surgery and 6 months after surgery were extracted and compared. Urinary incontinence was evaluated by the number of pads used at 1, 3, 6, and 12 months after surgery, and urinary continence was defined as 1 pad or less per day.
Results
The median age (interquartile) was 71 (64.0-74.0) years, BMI was 24.5 (22.7-26.1) kg/m2, and PSA was 6.4 (4.7-9.0) ng/mL. There were 13 cases (32.5%) with cT1 and 27 cases (67.5%) with cT2. In the NCCN risk classification, there were 1 (2.5%), 8 (20.0%), 25 (62.5%), 4 (10.0%), and 2 (5.0%) cases in the very low risk, low risk, intermediate favarable risk, intermediate unfavarable risk, and high risk categories, respectively. PV was 30.7 (24.8-49.2) mL, MUL was 11.4 (9.5-13.6) mm, and the console time was 164.0 (134.5-219.3) min. Nerve preservation was performed in 39 cases (97.5%), and lymph node dissection was performed in 2 cases (5.0%). The urinary continence rate was 31/40 (77.5%) at 1 month post-surgery, 33/40 (82.5%) at 3 months post-surgery, 36/40 (90.0%) at 6 months post-surgery, and 37/40 (92.5%) at 12 months post-surgery. In PFS, detrusor pressure at maximum flow, post-void residual urine volume, and bladder outlet obstruction index decreased at 6 months post-surgery compared to pre-surgery, while maximum urine flow rate and voided volume increased at 6 months post-surgery compared to pre-surgery. Detrusor overactivity (DO) was observed in 12 cases (30.0%), but it disappeared in 9 of these cases (75.0%).
Interpretation of results
In this prospective cohort, RS-RARP was associated with a high urinary continence rate from the early postoperative period. Urodynamic assessment revealed reduced voiding pressure and outlet obstruction parameters, as well as improved urinary flow and bladder emptying at 6 months postoperatively. Furthermore, DO was resolved in 75% of patients who had DO. These results suggest that postoperative continence recovery after RS-RARP may be related not only to preservation of periurethral supportive structures, but also to favorable changes in lower urinary tract function.