The mechanism of urinary incontinence after robotic-assisted laparoscopic radical prostatectomy (RaLRP) is not fully understood, and effective strategies for improving continence outcomes remain elusive. Recent studies suggest that preoperative membranous urethral length (MUL) is a key predictor of postoperative continence. This study aims to assess the impact of preoperative MUL on 12-month continence outcomes following RaLRP in a Chinese population at a tertiary center.

This retrospective study includes all RaLRP procedures performed at a tertiary center from January 2018 to July 2023. Patients receiving adjuvant radiotherapy, with follow-up shorter than one year, or of non-Chinese ethnicity were excluded, along with those without accessible magnetic resonance imaging (MRI) images. Data were extracted from electronic patient records and analyzed using SPSS Statistics (IBM, New York, USA). Preoperative MUL was measured between the prostate apex and penile bulb using sagittal T2-weighted MRI, and independently reviewed by two urologists. The primary outcome was the association between 12-month urinary continence, defined as zero pads used, and preoperative MUL.

A total of 288 patients were analyzed, with ages ranging from 51 to 81 years (mean age 67.7). The median MUL was 15.2 mm, with a range from 4.1 to 27.1 mm. At the 12-month follow-up post-RaLRP, patients required an average of 0.75 pads, and 63.2% of patients achieved continence. A greater MUL was significantly linked to a lower risk of incontinence at 12 months (OR 0.859, 95% CI 0.784 – 0.942, p = 0.001). Other variables, such as age, preoperative PSA levels, prostate volume, nerve-sparing status, and tumor staging, showed no significant impact on continence outcomes. Patients with an MUL of less than 15 mm exhibited a continence rate of 48.9%, lower than the 76.9% observed in those with an MUL greater than 15 mm (p < 0.01). Among those with an MUL below 10 mm, the continence rate was the lowest at 36.4%. However, there was no significant difference in continence rates between patients with MUL less than 10 mm and those with MUL between 10 and 15 mm (p = 0.116). Similarly, no significant difference in continence rates was found between patients with MUL from 15 to 20 mm and those greater than 20 mm (p = 0.413).

Our findings suggest that preoperative MUL is a critical predictor of postoperative continence following RaLRP. Routine measurement of MUL would enhance counseling and enable informed decisions regarding treatment options, especially for patients with an MUL of less than 15 mm.