Abstract
Background
Post-prostatectomy urinary continence recovery varies over time. We aimed to identify factors associated with continence recovery at different postoperative stages after robot-assisted radical prostatectomy (RARP) using pre- and postoperative multiparametric magnetic resonance imaging (mpMRI).
Methods
We retrospectively enrolled 106 patients with prostate cancer who underwent RARP at a single center between January 2020 and December 2024. All patients underwent mpMRI both preoperatively and postoperatively (postoperative MRI at 6±6 months). Continence was defined as 0 pad use per day, with follow-up for 12 months. On mpMRI, membranous urethral length (MUL), membranous urethral angle (MUA), and membranous urethral diameter (MUD) were measured, and derived indices such as MUL preservation ratio were calculated. Univariate analyses and multivariable logistic regression were performed to assess factors associated with continence recovery at catheter removal day 3 and at 1, 3, 6, and 12 months postoperatively. Receiver operating characteristic (ROC) analyses were used to evaluate predictive performance and determine optimal cut-off values.
Results
The mean age was 70.0±6.7 years. Continence rates increased from 11.3% at day 3 after catheter removal to 84.0% at 12 months. In univariate analyses, both preoperative and postoperative MUL were associated with continence recovery at multiple time points (all P<0.05), whereas MUA and MUD were not significant at any time point. In multivariable analyses, preoperative MUL was independently associated with continence recovery at day 3 [P=0.040; odds ratio (OR) =17.78; 95% confidence interval (CI): 1.14–278.47] and at 1 month (P=0.009; OR =11.33; 95% CI: 1.75–68.07). At 3 months, both preoperative MUL (P=0.030; OR =5.10; 95% CI: 1.17–22.19) and postoperative MUL (P=0.032; OR =6.01; 95% CI: 1.17–30.92) were independently associated with continence recovery. At 6 months, postoperative MUL showed marginal significance (P=0.051; OR =7.31; 95% CI: 0.97–32.47). At 12 months, age was independently associated with continence recovery (P=0.005; OR =5.65; 95% CI: 1.70–18.79). ROC analyses suggested acceptable discrimination for age [area under the curve (AUC) =0.697], preoperative MUL (AUC =0.919), postoperative MUL (AUC =0.902), and MUL preservation ratio (AUC =0.672), with optimal cut-offs of 73.5 years, 12.845 mm, 11.765 mm, and 91.5%, respectively. In patients with preoperative MUL <12.845 mm (n=71), postoperative MUL remained independently associated with mid- to long-term continence at 3, 6, and 12 months (all P≤0.001).
Conclusions
mpMRI-derived MUL metrics are stage-specific predictors of continence recovery after RARP. Preoperative MUL predicts early recovery, while postoperative MUL predicts mid-term recovery and retains prognostic value in patients with shorter preoperative MUL. Age is the primary independent predictor of 12-month continence.
Keywords: Robot-assisted radical prostatectomy (RARP), urinary incontinence, membranous urethral length (MUL), multiparametric magnetic resonance imaging (mpMRI), continence recovery
Highlight box.
Key findings
• In a retrospective cohort of 106 patients undergoing robot-assisted radical prostatectomy (RARP), continence (0 pad/day) improved from 11.3% at day 3 after catheter removal to 84.0% at 12 months.
• Preoperative membranous urethral length (MUL) on multiparametric magnetic resonance imaging (mpMRI) independently predicted early continence recovery (day 3 and 1 month), whereas postoperative MUL independently predicted mid-term recovery (3–6 months).
• Age was the primary independent predictor of 12-month continence recovery in the final model.
What is known and what is new?
• Preoperative MUL measured on magnetic resonance imaging (MRI) has been associated with post-prostatectomy continence outcomes.
• By incorporating both pre- and postoperative mpMRI measurements, we demonstrate stage-specific predictors of continence recovery and provide clinically useful cutoffs (preoperative MUL 12.845 mm; postoperative MUL 11.765 mm; age 73.5 years). Postoperative MUL remained predictive even among patients with shorter preoperative MUL.
What is the implication, and what should change now?
• These findings support maximizing preservation of MUL during RARP while maintaining oncologic principles, and may improve patient counseling by offering time-specific risk stratification for continence recovery.
Introduction
Prostate cancer is currently the second most common cancer among men worldwide (1), and both its incidence and related mortality continue to increase annually (2). Multiple treatment strategies are available for prostate cancer. For patients with localized and locally advanced disease, radical prostatectomy remains a standard treatment option (3). With the rapid development and widespread adoption of robotic technology, robot-assisted radical prostatectomy (RARP) has gradually replaced laparoscopic radical prostatectomy (LRP) and open retropubic radical prostatectomy (RRP), becoming a mainstream surgical approach for the management of prostate cancer (4).
Urinary incontinence is a common complication after radical prostatectomy and a major concern that influences patients’ decisions regarding surgical treatment. Although previous studies have suggested that RARP may provide superior long-term continence outcomes compared with conventional open and laparoscopic approaches, a substantial proportion of patients still experience postoperative incontinence (5). Existing evidence indicates that several factors, including age, prostate volume (PV), and preservation or reconstruction of periprostatic and periurethral anatomical structures, are associated to varying degrees with the likelihood of incontinence after RARP (6,7). Multiparametric magnetic resonance imaging (mpMRI) enables objective assessment of relevant anatomical factors; among these, preoperative membranous urethral length (MUL) has been identified as an independent risk factor for post-prostatectomy incontinence (8). However, objective evidence regarding the relationship between postoperative MUL and continence recovery after RARP remains limited, and the association between perioperative changes in magnetic resonance imaging (MRI)-derived anatomical parameters and postoperative continence recovery is yet to be fully elucidated.
Therefore, we conducted a retrospective analysis of patients with prostate cancer who underwent RARP at Huadong Hospital, Fudan University between January 2020 and December 2024, to systematically evaluate continence recovery at different postoperative stages. Using preoperative and postoperative mpMRI, we performed standardized measurements of MUL-related urethral anatomical parameters and examined their associations with continence recovery in conjunction with clinical variables. This study aims to clarify key factors associated with post-RARP incontinence, provide evidence to support preoperative counseling and treatment decision-making, and inform individualized surgical strategies and postoperative follow-up management. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0148/rc).
Methods
Clinical data
We retrospectively reviewed patients who underwent RARP for pathologically confirmed prostate cancer at Huadong Hospital, Fudan University between January 2020 and December 2024. During this period, 456 patients underwent RARP. Patients were screened according to predefined inclusion and exclusion criteria (see Figure S1). Forty-one patients were excluded because preoperative mpMRI was unavailable or unsuitable for standardized measurement, including cases in which preoperative MRI had been performed at outside institutions and the original imaging data were incomplete. An additional 298 patients were excluded because postoperative mpMRI was unavailable. Nine patients were excluded because follow-up was shorter than 12 months or they were lost to follow-up, and two patients were excluded because of a history of prior prostate surgery or documented urinary incontinence. Ultimately, 106 patients were included in the final analysis. Clinical variables collected included age, body mass index (BMI), preoperative prostate-specific antigen (PSA), PV, postoperative pathological Gleason score, surgical margin status, tumor involvement ratio, and clinical stage. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of Huadong Hospital Affiliated to Fudan University, and individual consent for this retrospective analysis was waived.
Surgical procedure
All patients underwent RARP under general anesthesia with endotracheal intubation using the da Vinci surgical system in the steep Trendelenburg position. After establishing pneumoperitoneum, radical prostatectomy was performed following standard steps, including dissection of the prostate and bladder neck, control of the dorsal venous complex, mobilization of the seminal vesicles and vas deferens, posterior dissection to the prostatic apex, and transection of the urethra with maximal preservation of the membranous urethra whenever feasible. Standard pelvic lymph node dissection was performed when indicated. Nerve-sparing was attempted in patients deemed suitable based on preoperative assessment and intraoperative findings. Vesicourethral anastomosis was completed, with bladder neck reconstruction performed when necessary. A urethral catheter was placed at the end of the procedure.
Postoperative follow-up and continence assessment
All patients completed effective postoperative follow-up for at least 12 months. Follow-up assessments included continence status and PSA level at day 3 after catheter removal and at 1, 3, 6, and 12 months postoperatively. Continence was evaluated using pad usage: urinary incontinence was defined as the use of ≥1 pad per day, whereas complete continence was defined as 0 pad per day (prophylactic use of an occasional dry pad without leakage was considered continent, as previously described) (9).
MRI protocol and measurements
Preoperative MRI was performed within 1 week prior to prostate biopsy. For the present study, only patients with available preoperative and postoperative pelvic mpMRI were included. Postoperative MRI was performed at 6±6 months after surgery. MRI was acquired using a 3.0-T Siemens scanner with a phased-array body coil. The imaging protocol covered the prostate bed and seminal vesicles and included axial, sagittal, and coronal fast spin-echo T2-weighted imaging (T2WI) and axial T1-weighted imaging (T1WI).
Measurements were performed on T2WI: MUL and membranous urethral angle (MUA) were measured on the mid-sagittal plane, and membranous urethral diameter (MUD) was measured on axial images at the widest portion of the membranous urethra (10) (measurement details are shown in Figure 1). Preoperative MUL was defined as the length of the membranous urethra from the bulb of the penis to the prostatic apex, and postoperative MUL as the distance from the bulb of the penis to the vesicourethral anastomosis. The MUL preservation ratio was calculated as postoperative MUL divided by preoperative MUL multiplied by 100%. MUL difference was calculated as preoperative MUL minus postoperative MUL. The absolute change in MUA was defined as the absolute value of postoperative MUA minus preoperative MUA (11).
Figure 1.
mpMRI-based measurement of urethral parameters on T2-weighted images. (A) Mid-sagittal T2-weighted image showing measurement of MUL and MUA relative to the horizontal reference line. (B) Axial T2-weighted image showing measurement of MUD. mpMRI, multiparametric magnetic resonance imaging; MUA, membranous urethral angle; MUD, membranous urethral diameter; MUL, membranous urethral length.
Image review and measurement procedure
All MRI measurements were independently performed by two urologists who had received dedicated training from radiologists in pelvic MRI interpretation and measurement, using a standardized protocol (Figure 1). Both readers were blinded to the patients’ clinical data and continence outcomes during image review and measurement recording. After the independent measurements were completed, the two readers cross-checked the results. For cases in which the measurements were discrepant, the anatomical landmarks were unclear, or the selected imaging plane differed, the two readers jointly reviewed the original MRI images and reached a consensus. The consensus value was used for the final statistical analysis.
Statistical analysis
Univariate and multivariable analyses were performed to identify factors associated with continence recovery at day 3 after catheter removal and at 1, 3, 6, and 12 months after RARP. Statistical analyses were conducted using SPSS version 27.0. Continuous variables were expressed as mean ± standard deviation and compared using the independent-samples t-test or the Mann-Whitney U test, as appropriate. Categorical variables were presented as number (percentage) and compared using the Chi-squared test or Fisher’s exact test, as appropriate. Variables with P<0.10 in univariate analyses were entered into multivariable logistic regression models. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were reported. A two-sided P≤0.05 was considered statistically significant.
Results
Baseline characteristics and continence recovery rates
All 106 patients successfully underwent RARP, with complete clinical and follow-up data. Baseline characteristics are summarized in Table 1, and MRI-derived measurements are shown in Table 2. Continence recovery rates increased over time: 11.3% (12/106) at day 3 after catheter removal, 24.5% (26/106) at 1 month, 46.2% (49/106) at 3 months, 66.0% (70/106) at 6 months, and 84.0% (89/106) at 12 months (Figure 2).
Table 1. Baseline characteristics of the study cohort (n=106).
| Characteristic | Value |
|---|---|
| Age, years | 70±6.70 |
| BMI, kg/m2 | 24.28±3.46 |
| PSA, ng/mL | 16.27±18.85 |
| Prostate volume, mL | 40.54±20.61 |
| ISUP grade group | |
| 1 | 3 (2.8) |
| 2 | 29 (27.4) |
| 3 | 43 (40.6) |
| 4 | 15 (14.2) |
| 5 | 16 (15.1) |
| Pathologic T stage | |
| pT2 | 59 (55.7) |
| pT3 | 45 (42.5) |
| pT4 | 2 (1.9) |
| Surgical margin | |
| Positive | 46 (43.4) |
| Negative | 60 (56.6) |
Data are presented as mean ± standard deviation or n (%). BMI, body mass index; ISUP, International Society of Urological Pathology; PSA, prostate-specific antigen; T, tumor.
Table 2. Preoperative and postoperative mpMRI-derived urethral parameters (n=106).
| MRI parameter | Value |
|---|---|
| Preoperative MUL, mm | 12.11±1.52 |
| Postoperative MUL, mm | 10.98±1.58 |
| MUL preservation ratio, % | 90.58±5.44 |
| MUL difference, mm | 1.13±0.66 |
| Preoperative MUA, degrees | 67.91±5.72 |
| Postoperative MUA, degrees | 74.83±4.73 |
| Absolute change in MUA, degrees | 7.18±4.45 |
| Preoperative MUD, mm | 9.83±0.56 |
| Postoperative MUD, mm | 9.74±0.60 |
Data are presented as mean ± standard deviation. Postoperative mpMRI was performed at 6±6 months after surgery. MUL preservation ratio = postoperative MUL/preoperative MUL ×100%. MUL difference = preoperative MUL − postoperative MUL. Absolute change in MUA = |postoperative MUA − preoperative MUA|. mpMRI, multiparametric magnetic resonance imaging; MUA, membranous urethral angle; MUD, membranous urethral diameter; MUL, membranous urethral length.
Figure 2.
Continence recovery over time after RARP (n=106). Stacked bars show the proportions of patients with complete continence (0 pad per day) and incontinence (≥1 pad per day) at day 3 after catheter removal and at 1, 3, 6, and 12 months after surgery. The embedded table provides the corresponding percentages at each follow-up time point. d, days; m, months; RARP, robot-assisted radical prostatectomy.
Univariate analysis
Using complete continence (0 pad) at each follow-up time point as the outcome, univariate analyses were performed for age, BMI, preoperative PSA, PV, tumor involvement ratio, surgical margin status, pathological stage, International Society of Urological Pathology (ISUP) grade, and MRI-related parameters (pre- and postoperative MUL, MUL preservation ratio, MUL difference, pre- and postoperative MUA and its absolute change, and pre- and postoperative MUD) (Table 3). At day 3 after catheter removal, preoperative MUL (P<0.001), postoperative MUL (P<0.001), and MUL preservation ratio (P=0.045) were significant. At 1 month, preoperative MUL (P<0.001), postoperative MUL (P<0.001), MUL preservation ratio (P=0.003), and MUL difference (P=0.03) were significant. At 3 months, only preoperative MUL (P<0.001) and postoperative MUL (P<0.001) remained significant. At 6 months, preoperative MUL (P=0.003), postoperative MUL (P=0.001), and ISUP grade (P=0.044) were significant. At 12 months, age (P=0.002), preoperative MUL (P=0.001), and postoperative MUL (P<0.001) were significant. MUA- and MUD-related variables were not significant at any time point.
Table 3. Univariate analysis of factors associated with complete continence (0 pad) at each follow-up time point (n=106).
| Variable | P value | ||||
|---|---|---|---|---|---|
| 3 d | 1 m | 3 m | 6 m | 12 m | |
| Age | 0.81 | 0.25 | 0.25 | 0.050* | 0.002* |
| BMI | 0.39 | 0.21 | 0.70 | 0.49 | 0.07 |
| Preoperative PSA | 0.83 | 0.21 | 0.26 | 0.41 | 0.99 |
| Prostate volume | 0.55 | 0.93 | 0.50 | 0.92 | 0.89 |
| Pathologic T stage | 0.84 | 0.81 | 0.91 | 0.66 | 0.80 |
| ISUP grade group | 0.30 | 0.19 | 0.15 | 0.04 | 0.23 |
| Tumor involvement ratio | 0.68 | 0.73 | 0.46 | 0.67 | 0.99 |
| Surgical margin status | 0.62 | 0.55 | 0.19 | 0.07 | 0.16 |
| Preoperative MUL | <0.001* | <0.001* | <0.001* | <0.001* | 0.001* |
| Postoperative MUL | <0.001* | <0.001* | <0.001* | <0.001* | <0.001* |
| MUL preservation ratio | 0.045* | 0.003* | 0.07 | 0.49 | 0.13 |
| MUL difference | 0.139 | 0.03* | 0.45 | 0.80 | 0.62 |
| Preoperative MUA | 0.890 | 0.82 | 0.82 | 0.34 | 0.53 |
| Postoperative MUA | 0.613 | 0.81 | 0.49 | 0.66 | 0.80 |
| Absolute change in MUA | 0.890 | 0.11 | 0.82 | 0.89 | 0.92 |
| Preoperative MUD | 0.495 | 0.57 | 0.70 | 0.88 | 0.72 |
| Postoperative MUD | 0.587 | 0.31 | 0.44 | 0.13 | 0.72 |
The outcome was complete continence, defined as 0 pad per day, assessed at day 3 after catheter removal and at 1, 3, 6, and 12 months after surgery. P values are from univariate analyses comparing continent versus incontinent patients at each time point. Continuous variables were compared using the independent-samples t-test or Mann-Whitney U test, and categorical variables using the Chi-squared test or Fisher’s exact test, as appropriate. P values were used for variable screening (P<0.10) for subsequent multivariable logistic regression analyses. *, significant P values (two-sided P≤0.05). BMI, body mass index; d, days; ISUP, International Society of Urological Pathology; m, months; MUA, membranous urethral angle; MUD, membranous urethral diameter; MUL, membranous urethral length; PSA, prostate-specific antigen; T, tumor.
Multivariable logistic regression analysis
Variables with P<0.10 in univariate analyses were entered into multivariable logistic regression models (Table 4). Preoperative MUL was independently associated with complete continence at day 3 (P=0.040; OR =17.78; 95% CI: 1.14–278.47) and at 1 month (P=0.009; OR =11.33; 95% CI: 1.75–68.07). At 3 months, both preoperative MUL (P=0.03; OR =5.10; 95% CI: 1.17–22.19) and postoperative MUL (P=0.03; OR =6.01; 95% CI: 1.17–30.92) were independently associated with continence recovery. At 6 months, postoperative MUL showed marginal significance (P=0.051; OR =7.31; 95% CI: 0.97–32.47). At 12 months, age was independently associated with continence recovery (P=0.005; OR =5.65; 95% CI: 1.70–18.79). In addition, when patients were stratified by surgical margin status, no significant differences were observed in postoperative MUL (P=0.47) or MUL preservation ratio (P=0.46) between margin-positive and margin-negative groups.
Table 4. Multivariable logistic regression analyses for complete continence (0 pad) at each follow-up time point (n=106).
| Variable | 3 d | 1 m | 3 m | 6 m | 12 m | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | |||||
| Age | 0.56 | 0.57 (0.08–3.88) | 0.67 | 1.37 (0.33–5.96) | 0.46 | 1.48 (0.52–4.19) | 0.06 | 2.56 (0.95–6.91) | 0.005 | 5.65 (1.70–18.79) | ||||
| Preoperative MUL | 0.040 | 17.78 (1.14–278.47) | 0.009 | 11.33 (1.75–68.07) | 0.03 | 5.10 (1.17–22.19) | 0.09 | 5.02 (0.74–34.05) | 0.18 | 5.381 (0.97–13.47) | ||||
| Postoperative MUL | 0.37 | 3.81 (0.20–71.07) | 0.06 | 6.79 (1.03–55.85) | 0.03 | 6.01 (1.17–30.92) | 0.051 | 7.311 (0.97–32.47) | 0.36 | 3.591 (0.70–13.37) | ||||
| MUL preservation ratio | 0.27 | 3.01 (0.42–21.68) | 0.63 | 1.48 (0.16–3.94) | 0.56 | 0.72 (0.24–2.20) | 0.18 | 0.50 (0.18–1.40) | 0.33 | 1.75 (0.56–5.42) | ||||
The outcome was complete continence, defined as 0 pad per day, assessed at each time point. ORs are presented with 95% CIs. Age was included as a dichotomous variable using the optimal cut-off value of 73.5 years; the reference category was age <73.5 years. Candidate variables with P<0.10 in univariate analyses were entered into the multivariable models. All tests were two-sided, and P≤0.05 was considered statistically significant. CI, confidence interval; d, days; m, months; MUL, membranous urethral length; OR, odds ratio.
Receiver operating characteristic (ROC) analysis and optimal cut-off values (12-month continence as the endpoint)
ROC analyses were conducted to evaluate the discriminative performance of age, preoperative MUL, postoperative MUL, and MUL preservation ratio for 12-month continence recovery (0 pad), and optimal cut-offs were determined using the Youden index (Figure 3). Age yielded an AUC of 0.697 (P=0.01; 95% CI: 0.562–0.831) with an optimal cut-off of 73.5 years (sensitivity 74.2%, specificity 64.7%). Preoperative MUL yielded an AUC of 0.919 (P<0.001; 95% CI: 0.866–0.971) with a cut-off of 12.845 mm (sensitivity 88.5%, specificity 85.0%). Postoperative MUL yielded an AUC of 0.902 (P<0.001; 95% CI: 0.837–0.968) with a cut-off of 11.765 mm (sensitivity 88.5%, specificity 85.0%). MUL preservation ratio yielded an AUC of 0.672 (P=0.009; 95% CI: 0.550–0.793) with a cut-off of 91.5% (sensitivity 76.9%, specificity 56.2%). Overall, preoperative and postoperative MUL demonstrated good discrimination for 12-month continence recovery.
Figure 3.
ROC curves for predicting complete continence (0 pad) after RARP. (A) Age. (B) Preoperative MUL. (C) Postoperative MUL. (D) MUL preservation ratio. The AUC with 95% CI and corresponding P value are shown in each panel. AUC, area under the curve; CI, confidence interval; MUL, membranous urethral length; RARP, robot-assisted radical prostatectomy; ROC, receiver operating characteristic.
Kaplan-Meier analysis
Kaplan-Meier curves were generated to compare time to continence recovery across strata defined by the optimal cut-offs for preoperative MUL and postoperative MUL (Figure 4). Log-rank tests indicated that patients with preoperative MUL >12.845 mm and those with postoperative MUL >11.765 mm achieved continence recovery faster than their respective counterparts (both P<0.001).
Figure 4.
Kaplan-Meier curves of time to continence recovery after RARP. (A) Continence recovery stratified by preoperative MUL using the cutoff of 12.845 mm (>12.845 vs. ≤12.845 mm). (B) Continence recovery stratified by postoperative MUL using the cutoff of 11.765 mm (>11.765 vs. ≤11.765 mm). Complete continence was defined as 0 pad per day. P values were calculated using the log-rank test. MUL, membranous urethral length; RARP, robot-assisted radical prostatectomy. Code 0 = no; code 1 = yes.
Subgroup analysis in patients with shorter preoperative MUL
A prespecified subgroup analysis was conducted in patients with shorter preoperative MUL (<12.845 mm; n=71). In univariate analyses, postoperative MUL was significantly associated with continence recovery at 3, 6, and 12 months (all P<0.001), and age was significant at 12 months (P=0.009) (Table 5). In multivariable analyses, postoperative MUL remained independently associated with continence recovery at 3 months (P=0.001; OR =3.28; 95% CI: 1.63–6.57), 6 months (P<0.001; OR =6.05; 95% CI: 2.50–14.65), and 12 months (P<0.001; OR =8.48; 95% CI: 3.02–28.51) (Table 6).
Table 5. Univariate analysis of factors associated with complete continence (0 pad) in patients with shorter preoperative MUL (<12.845 mm) (n=71).
| Variable | P value | |||
|---|---|---|---|---|
| 1 m | 3 m | 6 m | 12 m | |
| Age | 0.74 | 0.78 | 0.65 | 0.009 |
| BMI | 0.17 | 0.64 | 0.33 | 0.051 |
| Preoperative PSA | 0.63 | 0.38 | 0.90 | 0.71 |
| Prostate volume | 0.50 | 0.30 | 0.89 | 0.62 |
| Tumor involvement ratio | 0.42 | 0.35 | 0.93 | 0.40 |
| Surgical margin status | 0.67 | 0.40 | 0.20 | 0.19 |
| Postoperative MUL | 0.06 | <0.001* | <0.001* | <0.001* |
| MUL preservation ratio | 0.85 | 0.34 | 0.80 | 0.78 |
| MUL difference | 0.94 | 0.67 | 0.82 | 0.48 |
| Preoperative MUA | 0.97 | 0.60 | 0.57 | 0.68 |
| Postoperative MUA | 0.71 | 0.03 | 0.39 | 0.85 |
| Absolute change in MUA | 0.92 | 0.20 | 0.22 | 0.84 |
| Preoperative MUD | 0.44 | 0.44 | 0.58 | 0.97 |
| Postoperative MUD | 0.57 | 0.86 | 0.78 | 0.30 |
The outcome was complete continence, defined as 0 pad per day, assessed at 1, 3, 6, and 12 months after surgery. P values are from univariate comparisons between continent and incontinent patients at each time point. Continuous variables were compared using the independent-samples t test or Mann-Whitney U test, and categorical variables using the Chi-squared test or Fisher’s exact test, as appropriate. P values were used for variable screening (P<0.10) for subsequent multivariable logistic regression analyses in this subgroup. *, significant P values (two-sided P≤0.05). BMI, body mass index; m, months; MUA, membranous urethral angle; MUD, membranous urethral diameter; MUL, membranous urethral length; PSA, prostate-specific antigen.
Table 6. Multivariable logistic regression analyses for complete continence (0 pad) in patients with shorter preoperative MUL (<12.845 mm) (n=71).
| Variable | 1 m | 3 m | 6 m | 12 m | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | ||||
| Age (per 1-year increase) | 0.62 | 1.04 (0.88–1.24) | 0.79 | 1.01 (0.93–1.10) | 0.41 | 1.04 (0.95–1.13) | 0.07 | 0.88 (0.76–1.03) | |||
| Postoperative MUL (per 1-mm increase) | 0.08 | 3.73 (0.82–16.91) | 0.001* | 3.28 (1.63–6.57) | <0.001* | 6.05 (2.50–14.65) | <0.001* | 8.48 (3.02–28.51) | |||
The outcome was complete continence, defined as 0 pad per day, assessed at 1, 3, 6, and 12 months after surgery. ORs are presented with 95% CIs. Age and postoperative MUL were modeled as continuous variables to preserve information and statistical power in this relatively small subgroup and to avoid loss of information from dichotomization. Candidate variables with P<0.10 in univariate analyses were entered into the multivariable models for this subgroup. *, significant P values (two-sided P≤0.05). CI, confidence interval; m, months; MUL, membranous urethral length; OR, odds ratio.
Discussion
Urinary incontinence is one of the most common and quality-of-life–limiting complications after radical prostatectomy. Its pathophysiology is multifactorial, involving injury to the external urethral sphincter complex and its innervation, alterations in local blood supply, and postoperative bladder dysfunction (12). Previous studies have suggested that RARP achieves oncologic outcomes comparable to LRP and open RRP, while potentially offering advantages in operative time, blood loss, and long-term functional recovery of continence and sexual function (5). Nevertheless, postoperative incontinence remains clinically relevant. In our cohort, 14% of patients had not achieved complete continence (0 pad) at 12 months, underscoring the need to further optimize functional outcomes after RARP.
Preoperative MUL has been consistently identified as an independent factor associated with post-prostatectomy incontinence risk (8). Most studies measure preoperative MUL on mid-sagittal MRI as the length of the membranous urethra from the bulb of the penis to the prostatic apex. In contrast, the literature on postoperative MUL and continence recovery is heterogeneous in measurement strategies. Postoperative MUL has been estimated semi-quantitatively using a 16-Fr catheter as a reference (13), measured intraoperatively with a ruler prior to urethral transection (14), or derived from histologic measurements of urethral tissue in the prostate specimen and compared with preoperative MRI to calculate the preserved proportion (15). Collectively, these studies suggest that preserving a longer urethral length is beneficial for postoperative continence recovery. However, such approaches may be susceptible to measurement bias due to intraoperative traction, limited visualization, and the precision of measurement tools. Therefore, we included patients who underwent both pre- and postoperative MRI and applied a standardized imaging-based protocol to objectively quantify postoperative MUL. In parallel, we assessed additional parameters, including MUA and MUD, to further clarify their relationships with continence recovery after RARP. This approach is also supported by a recent bi-parametric MRI study showing that both preoperative and postoperative MUL measurements were associated with continence after RARP, whereas MUD and PV had limited prognostic value (16).
Continence recovery after radical prostatectomy is influenced by multiple factors, with converging evidence highlighting functional changes in the external urethral sphincter complex and pelvic floor support structures as key determinants (17). In this study, a longer preoperative MUL was independently associated with better early continence recovery (day 3 after catheter removal, and at 1 and 3 months), consistent with prior reports (8). Clinically, this finding supports proactive preoperative counseling for patients with shorter preoperative MUL regarding a potentially delayed continence recovery trajectory. It also highlights the importance of perioperative pelvic floor muscle training and, when oncologically appropriate, surgical strategies aimed at preserving and reconstructing pelvic floor anatomy to mitigate the functional disadvantage associated with unfavorable baseline anatomy.
Importantly, our results further suggest that a longer postoperative MUL is independently associated with continence recovery at 3 months and shows marginal significance at 6 months. In the subgroup of patients with shorter preoperative MUL, postoperative MUL remained significantly associated with continence recovery from 3 to 12 months, indicating that postoperative MUL may have enhanced discriminative value among patients with unfavorable preoperative anatomy. In addition, we did not observe significant differences in postoperative MUL or MUL preservation ratio between margin-positive and margin-negative groups, suggesting that, in appropriately selected patients, attempts to preserve MUL may not necessarily compromise surgical margin status. However, this observation should be interpreted cautiously and warrants confirmation in larger prospective cohorts. Taken together, our findings support the concept that maximizing membranous urethral preservation and optimizing anastomotic/reconstructive techniques—while maintaining oncologic safety—may contribute to improved continence outcomes. This interpretation is broadly consistent with previous studies emphasizing maximal urethral length preservation as a determinant of early continence recovery (18). At the same time, recent evidence from holmium laser enucleation of the prostate (HoLEP) suggests that MUL may reflect a more general concept of functional urethral reserve across prostate procedures, although the mechanisms are not directly equivalent to those of RARP (19).
Regarding MUA and MUD, prior studies have reported inconsistent associations with continence recovery (20). Recent work has also extended MRI-based evaluation beyond simple urethral length to three-dimensional membranous urethral parameters, suggesting that a larger membranous urethral complex volume may be associated with earlier continence recovery after RARP (21). In our study, neither preoperative nor postoperative MUA or MUD showed significant associations with continence recovery at any follow-up time point. Differences in measurement planes, anatomical landmarks, and parameter definitions across studies may partly account for the observed heterogeneity. Further investigations with standardized measurement protocols and multi-center datasets are needed to clarify the potential role of these parameters.
At 12 months postoperatively, age was independently associated with continence recovery, with younger patients showing a higher likelihood of achieving complete continence. Previous studies have similarly suggested that age may be associated with inferior continence outcomes after radical prostatectomy (22). However, whether age remains a stable risk factor in the RARP era remains debated (23). With ongoing advances in surgical technique, perioperative management, and continence-preserving strategies, the magnitude of the age effect may evolve over time. Additional research is needed to determine the robustness of age as a predictor across surgical platforms and contemporary practice settings.
The relationship between PV and postoperative continence recovery remains controversial (24). In our cohort, PV was not significantly associated with continence recovery within 12 months after RARP. PV is commonly estimated using the ellipsoid formula (0.52 × anteroposterior × transverse × craniocaudal diameters), and inter-operator variability in boundary delineation may introduce measurement error. Such variability may contribute to inconsistencies across studies.
Obesity, typically assessed using BMI, has been reported as a risk factor for unfavorable continence outcomes after LRP in some studies (25). In our analysis, BMI was not significantly associated with continence recovery. One potential explanation is that BMI itself may not directly determine continence outcomes; rather, obesity-related alterations in pelvic floor structure and function may mediate the association. However, evidence on pelvic floor dysfunction among obese men remains limited (26), and further studies are required to clarify the relationship between obesity, pelvic floor function, and post-prostatectomy continence recovery.
This study has several limitations. First, this was a retrospective, single-center study with a moderate sample size and without external validation, which may limit generalizability. In addition, because only patients with available postoperative mpMRI were included, selection bias could not be excluded. Second, continence status was assessed using pad usage and may be subject to patient-reported bias. Third, objective functional assessments such as postoperative urodynamic testing were unavailable, limiting mechanistic interpretation of the relationship between anatomical parameters and continence recovery. Fourth, although all MRI parameters were independently measured by two trained readers under blinded conditions and discrepancies were resolved by consensus, formal inter-observer agreement statistics could not be calculated because the paired duplicate measurement records were not available for complete retrospective retrieval. Future multi-center prospective studies incorporating standardized imaging measurements, reproducibility assessment, and urodynamic evaluation are warranted to more comprehensively elucidate the interplay between perioperative anatomical changes and continence recovery after RARP.
Conclusions
In patients undergoing RARP, mpMRI-derived MUL metrics were associated with continence recovery. Preoperative MUL was independently associated with early recovery, whereas postoperative MUL was associated with mid-term recovery and remained informative in patients with shorter preoperative MUL. At 12 months, continence recovery was primarily associated with age. Larger multicenter studies are warranted for validation.
Supplementary
The article’s supplementary files as
Acknowledgments
None.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of Huadong Hospital Affiliated to Fudan University, and individual consent for this retrospective analysis was waived.
Footnotes
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0148/rc
Funding: This study was supported by Huadong Hospital Key Specialized Disease Construction (No. ZDZB2222).
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0148/coif). All authors report receiving support from Huadong Hospital Key Specialized Disease Construction. The authors have no other conflicts of interest to declare.
Data Sharing Statement
Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0148/dss
References
- 1.Bray F, Laversanne M, Sung H, et al. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2024;74:229-63. 10.3322/caac.21834 [DOI] [PubMed] [Google Scholar]
- 2.James ND, Tannock I, N'Dow J, et al. The Lancet Commission on prostate cancer: planning for the surge in cases. Lancet 2024;403:1683-722. 10.1016/S0140-6736(24)00651-2 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Cornford P, van den Bergh RCN, Briers E, et al. EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer-2024 Update. Part I: Screening, Diagnosis, and Local Treatment with Curative Intent. Eur Urol 2024;86:148-63. [DOI] [PubMed] [Google Scholar]
- 4.Coughlin GD, Yaxley JW, Chambers SK, et al. Robot-assisted laparoscopic prostatectomy versus open radical retropubic prostatectomy: 24-month outcomes from a randomised controlled study. Lancet Oncol 2018;19:1051-60. 10.1016/S1470-2045(18)30357-7 [DOI] [PubMed] [Google Scholar]
- 5.Carbonara U, Srinath M, Crocerossa F, et al. Robot-assisted radical prostatectomy versus standard laparoscopic radical prostatectomy: an evidence-based analysis of comparative outcomes. World J Urol 2021;39:3721-32. 10.1007/s00345-021-03687-5 [DOI] [PubMed] [Google Scholar]
- 6.Kim M, Park M, Pak S, et al. Integrity of the Urethral Sphincter Complex, Nerve-sparing, and Long-term Continence Status after Robotic-assisted Radical Prostatectomy. Eur Urol Focus 2019;5:823-30. 10.1016/j.euf.2018.04.021 [DOI] [PubMed] [Google Scholar]
- 7.de Carvalho PA, Barbosa JABA, Guglielmetti GB, et al. Retrograde Release of the Neurovascular Bundle with Preservation of Dorsal Venous Complex During Robot-assisted Radical Prostatectomy: Optimizing Functional Outcomes. Eur Urol 2020;77:628-35. 10.1016/j.eururo.2018.07.003 [DOI] [PubMed] [Google Scholar]
- 8.Breyer BN, Kim SK, Kirkby E, et al. Updates to Incontinence After Prostate Treatment: AUA/GURS/SUFU Guideline (2024). J Urol 2024;212:531-8. 10.1097/JU.0000000000004088 [DOI] [PubMed] [Google Scholar]
- 9.Machioka K, Kadono Y, Naito R, et al. Evaluating urinary incontinence before and after radical prostatectomy using the international consultation on incontinence questionnaire-short form. Neurourol Urodyn 2019;38:726-33. 10.1002/nau.23907 [DOI] [PubMed] [Google Scholar]
- 10.Paparel P, Akin O, Sandhu JS, et al. Recovery of urinary continence after radical prostatectomy: association with urethral length and urethral fibrosis measured by preoperative and postoperative endorectal magnetic resonance imaging. Eur Urol 2009;55:629-37. 10.1016/j.eururo.2008.08.057 [DOI] [PubMed] [Google Scholar]
- 11.Veerman H, Hagens MJ, Hoeks CM, et al. A standardized method to measure the membranous urethral length (MUL) on MRI of the prostate with high inter- and intra-observer agreement. Eur Radiol 2023;33:3295-302. 10.1007/s00330-022-09320-2 [DOI] [PubMed] [Google Scholar]
- 12.Heesakkers J, Farag F, Bauer RM, et al. Pathophysiology and Contributing Factors in Postprostatectomy Incontinence: A Review. Eur Urol 2017;71:936-44. 10.1016/j.eururo.2016.09.031 [DOI] [PubMed] [Google Scholar]
- 13.Ando S, Kamei J, Yamazaki M, et al. Longer preserved urethral length in robot-assisted radical prostatectomy significantly contributes to post-operative urinary continence recovery. BJUI Compass 2022;3:184-90. 10.1002/bco2.128 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Ando S, Sugihara T, Hinotsu S, et al. Early recovery of urinary continence after robot-assisted radical prostatectomy is associated with membranous urethra and neurovascular bundle preservation. Int J Urol 2024;31:492-9. 10.1111/iju.15388 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Valenzi FM, Fuschi A, Al Salhi Y, et al. Is early continence recovery related to the length of spared urethra? A prospective multicenter study comparing preoperative MRI and histologic specimen measurements after robotic radical prostatectomy. Eur J Surg Oncol 2024;50:108319. [DOI] [PubMed] [Google Scholar]
- 16.Nolsøe AB, Løgager V, Boesen L, et al. Association of bi-parametric MRI measures with continence after robot-assisted radical prostatectomy. BJU Int 2025;135:603-10. 10.1111/bju.16594 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Kadono Y, Nohara T, Kawaguchi S, et al. Impact of Pelvic Anatomical Changes Caused by Radical Prostatectomy. Cancers (Basel) 2022;14:3050. 10.3390/cancers14133050 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Hamada A, Razdan S, Etafy MH, et al. Early return of continence in patients undergoing robot-assisted laparoscopic prostatectomy using modified maximal urethral length preservation technique. J Endourol 2014;28:930-8. 10.1089/end.2013.0794 [DOI] [PubMed] [Google Scholar]
- 19.Lee N, Benzouak T, Nguyen DD, et al. Membranous urethral length as a predictor for urinary incontinence after holmium enucleation of the prostate for benign prostatic hyperplasia. World J Urol 2026;44:138. 10.1007/s00345-026-06232-4 [DOI] [PubMed] [Google Scholar]
- 20.Soljanik I, Bauer RM, Becker AJ, et al. Is a wider angle of the membranous urethra associated with incontinence after radical prostatectomy? World J Urol 2014;32:1375-83. 10.1007/s00345-014-1241-5 [DOI] [PubMed] [Google Scholar]
- 21.Wang M, Deng R, Wang L, et al. Association between 3D membranous urethral parameters and urinary continence recovery after RARP. Eur J Med Res 2024;29:165. 10.1186/s40001-024-01758-y [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Tienza A, Akin Y, Rassweiler J, et al. A match-pair analysis of continence in intermediate and high-risk prostate cancer patients after robot-assisted radical prostatectomy: the role of urine loss ratio and predictive analysis. Prostate Int 2018;6:94-8. 10.1016/j.prnil.2017.09.001 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Leyh-Bannurah SR, Wagner C, Schuette A, et al. Feasibility of robot-assisted radical prostatectomy in men at senior age ≥75 years: perioperative, functional, and oncological outcomes of a high-volume center. Aging Male 2022;25:8-16. 10.1080/13685538.2021.2018417 [DOI] [PubMed] [Google Scholar]
- 24.Galfano A, Panarello D, Secco S, et al. Does prostate volume have an impact on the functional and oncological results of Retzius-sparing robot-assisted radical prostatectomy? Minerva Urol Nefrol 2018;70:408-13. 10.23736/S0393-2249.18.03069-2 [DOI] [PubMed] [Google Scholar]
- 25.Nitta M, Tazawa M, Takahashi K, et al. Variations in predictors for urinary continence recovery at different time periods following robot-assisted radical prostatectomy. Asian J Endosc Surg 2024;17:e13243. 10.1111/ases.13243 [DOI] [PubMed] [Google Scholar]
- 26.Chilaka C, Toozs-Hobson P, Chilaka V. Pelvic floor dysfunction and obesity. Best Pract Res Clin Obstet Gynaecol 2023;90:102389. 10.1016/j.bpobgyn.2023.102389 [DOI] [PubMed] [Google Scholar]