Pelvic anatomy on preoperative magnetic resonance imaging can predict early continence after robot-assisted radical prostatectomy

Background and Purpose: Postoperative incontinence is multifactorial after radical prostatectomy. Using endorectal coil MRI, we examined features of the male urethra and accompanying muscular sphincter to predict continence after robot-assisted radical prostatectomy (RARP). Patients and Methods: 80 patients underwent preoperative 1.5 Tesla endorectal coil MRI. Urethral length was measured in the coronal plane. All patients underwent RARP. Questionnaires were completed by patients at monthly intervals. The primary end point was time to continence defined as necessitating 0 to 1 pad per day (PPD). Statistical analysis was performed using Cox regression models to create both univariate and multivariate survival models. Results: Mean age was 59.7 (standard deviation [SD] 7.1); 98% had bilateral nerve sparing. Mean urethral length was 17.1mm (SD 4.5mm). Mean prostate size was 34.7 g (SD 17.8). By 3 months, 60 patients achieved 1 PPD (mean 8.1 weeks, SD 9.4) and 34 patients achieved 0 PPD (mean 10.5 weeks, SD 8.0). Time to social continence was significantly related to prostate size both as a continuous variable (P=0.01), and as a dichotomized variable of ≥50 vs<50 g (P=0.02). Increased urethral length was related to decreased time to continence both as a continuous variable (P=0.06), and when dichotomized to ≥20 vs<20mm (P=0.08). In addition to larger prostate size (hazard ratio [HR] 0.97, P<0.04), older age (0.95 P<0.025) was also associated with a longer time to achieve 0 PPD. Multivariate analysis revealed that longer urethral length was associated with a faster recovery of continence (HR 1.11, P<0.01). After controlling for age and urethral length, patients with a prostate size ≥50 g had 75% lower likelihood of achieving continence at all time points when compared with patients with prostate size <50 g (HR 0.25; 95% confidence interval: 0.06, 1.06; P=0.06). Conclusions: Longer urethral length increased the likelihood of achieving continence at all time points postoperatively. Advanced age and larger prostate size were negatively associated with continence outcomes.