Hypothesis / aims of study
Post-radical prostatectomy (RP) incontinence remains a major determinant of quality of life. While bilateral nerve-sparing (BNS) robot-assisted radical prostatectomy (RARP) improves outcomes, 10–30% of patients experience incontinence within 1 year despite optimal technique. We hypothesized that following bilateral full nerve-sparing (BNS) surgery, continence recovery is primarily determined by the integrity of the muscular sphincter complex, which in turn depends on the patient's preoperative anatomy. This study evaluates the impact of six key MRI-derived morphological features on achieving functional continence at 3, 6 and 12-month.
Study design, materials and methods
Patients who underwent transperitoneal BNS-RARP (Veccia grade 1) by five high-volume surgeons (Jan 2022–Jan 2024) in a tertiary center were prospectively enrolled in this study. Preoperative MRI-derived features - membranous urethral length (MUL, mm), bladder neck diameter (BND, mm), prostate volume (mL), neurovascular bundle orientation (lateral/posterolateral), presence of median lobe or intravesical prostatic protrusion and apical configuration (Lee type, A-D) - were recorded. Functional continence was defined as ≤1 pad/day at 3, 6, and 12 months. Comparative analysis was performed between the Continent group (CG) and the Incontinent group (IG) to identify predictors.
Results
Of 243 patients submitted to RARP during the study period, 73 had full bilateral nerve-sparing (Veccia grade 1). Mean age, BMI and prostate volume were 66.3 years, 25.6 kg/m² and 52.1 mL, respectively. Continence rates at 3, 6, and 12 months were 50.7%, 86.3% and 93%, respectively. CG had significantly greater MUL (18.7 mm vs 15.5 mm, p=0.032) and smaller BND (18.7 mm vs 20.9 mm, p=0.021) than IG. The BND/MUL ratio was also lower in those regaining continence (1.18 vs 1.44, p=0.04). ROC analysis found MUL, BND and BND/MUL ratio to be strong predictors (AUC: 0.84, 0.81 and 0.71). Higher prostate volume predicted early, but not late incontinence. Median lobe or prostatic protrusion increased persistent incontinence risk (OR 0.3; p=0.02). Lee type B/C showed a non-significant trend toward later recovery (p=0,07). Age and BMI had no statistical effect.
Interpretation of results
Our findings are consistent with existing literature demonstrating that membranous urethral length (MUL) is one of the strongest predictors of continence recovery after RARP, reinforcing its role as a surrogate of sphincteric functional reserve. Similarly, the negative impact of a wider bladder neck diameter (BND) aligns with prior studies suggesting that bladder neck configuration influences early continence outcomes.
Notably, the BND/MUL ratio provided additional predictive value, supporting the concept—less explored in the literature—that continence is determined by the balance between urethral length and outlet configuration rather than isolated parameters. This may represent a more integrative anatomical marker.
The association between median lobe/intravesical protrusion and worse outcomes is also in line with previous reports, likely reflecting increased surgical complexity and need for bladder neck reconstruction. In contrast, prostate volume appeared to affect early but not long-term continence, which has been variably reported in the literature.
Finally, the lack of association with age and BMI contrasts with some prior studies, possibly reflecting the homogeneity of our cohort and the standardized surgical technique. Overall, our results support growing evidence that MRI-based anatomical features are key determinants of continence recovery, even in optimally performed nerve-sparing surgery.