Objective: To identify a parameter predicting postoperative recovery of urinary continence after radical prostatectomy, associations between parameters on preoperative magnetic resonance imaging (MRI) and postoperative continence status were investigated. Methods: This prospective study enrolled 113 patients with localized prostate cancer who underwent MRI before radical prostatectomy. Continence was evaluated using the Expanded Prostate Index Composite instrument before surgery and at 1, 3, 6, 12, 18, 24, and 36 months postoperatively. We developed a novel parameter, minimal residual membranous urethral length (mRUL), defined as the distance between the lower margins of the puboperinealis and bulbospongiosus muscles in a direction parallel with the urethra on preoperative MRI, which is supposed to represent the minimal intact residual part of the membranous urethra during RP. Thicknesses of the levator ani and periurethral sphincter complex were also estimated on MRI. Results: Continence recovery was significantly faster in patients with longer mRUL (≥6.4 mm) than in patients with shorter mRUL (<6.4 mm; log-rank test, P =.003). Interestingly, incontinence rate before radical prostatectomy was significantly lower in patients with longer mRUL (2.0%) than in those with shorter mRUL (17.5%; P =.008). Multivariate analysis showed that longer mRUL was significantly related to superior continence recovery (hazard ratio, 0.78; P =.005). Thicknesses of the levator ani and periurethral sphincter complex were not associated with continence recovery. Conclusion: Preoperative mRUL offers an independent predictor of continence recovery after radical prostatectomy and is also associated with preoperative (baseline) continence status.
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