Membranous urethral length (MUL) loss following radical prostatectomy (RP) is a well-established risk factor for post-prostatectomy stress urinary incontinence (PPI) and continence recovery. (1) Prior studies using magnetic resonance imaging (MRI) have reported an average MUL of 1.13cm in men with PPI.(2) However, no studies to date have evaluated MUL using urodynamics (UDS), specifically through urethral pressure profiles (UPP), as a surrogate tool. 

The aim of this study is to compare MUL measurements in men who have undergone RP with those referred for UDS for non-RP-related indications, and to evaluate whether UPP-based MUL assessment could serve as a predictive tool for PPI.

A single-center retrospective review was conducted in men referred for UDS between 2012 and 2024. Due to the retrospective nature of the study, pre- and post- RP urethral length comparisons in the same patients were not feasible. Instead, MUL in men referred for UDS for reasons unrelated to RP served as a surrogate for pre-RP MUL. These patients were age-matched to the post-RP cohort. Patients with a diagnosis of neurogenic lower urinary tract disease (NLUTD), abdominoperineal resection, cystoprostatectomy and previous urethroplasty were excluded from the study. (Figure 1) UPP measurement was done using the Brown-Wickham technique with 8-Fr, single lumen, urethral catheters.

MUL data were available for 69 patients referred for PPI, as compared to 75 patients who did not have a RP. 10 of these patients were referred for presumed bladder outlet obstruction (BOO), 28 for overactive bladder (OAB) symptoms, 21 for combined OAB and BOO, 9 for underactive bladder (UAB), 4 for combined UAB and BOO, and 2 for unknown reasons. 8 of these patients had a transurethral resection of the prostate (TURP). 

Median MUL was 0.8cm (IQR 0.50 – 1.40) in men with PPI, compared to 3.9cm (IQR 0.20 – 4.98) in men without RP. Robotic-assisted laparoscopic radical prostatectomy (RALRP) was associated with longer MUL than open RP (O-RP) and was comparable to laparoscopic RP (L-RP) [0.9cm (RALRP) vs. 0.6cm (O-RP) vs. 0.9cm (L-RP)]. (Table 1)

RP is associated with a considerable reduction in MUL, with a median loss of 3.1 cm observed in our cohort. The average MUL measured using UPP in men with PPI (0.8 cm) closely aligns with values reported in previous MRI-based studies, reinforcing the validity of UPP as a measurement tool. The ability to measure MUL using UPP during  UDS offers a practical, non-radiological method of identifying patients at elevated risk of PPI. The ability to measure MUL pre-operatively could inform patient counselling by providing individualized risk assessments for PPI, helping to set realistic expectations and guide shared decision-making regarding treatment options. Post-operatively, UPP-derived MUL measurements may aid in stratifying patients who might benefit from early intervention, pelvic floor rehabilitation, or surgical management of incontinence.

UPP measurements during UDS offer an objective method for assessing MUL following RP. Our findings support the use of this approach as a surrogate marker for post-prostatectomy incontinence risk and potential aid in pre-operative counselling and planning. Further prospective, randomised, multi-center studies comparing UPP and UDS in pre- and post-prostatectomy patients would be welcome to validate these findings and expand their clinical applicability.

Fonseca J, Moraes-Fontes MF, Sousa I, Oliveira F, Froes G, Gaivão A, et al. Membranous urethral length is the single independent predictor of urinary continence recovery at 12 months following Retzius-sparing robot-assisted radical prostatectomy. Journal of Robotic Surgery. 2024;18(1):230.
Oza P, Walker NF, Rottenberg G, MacAskill F, Malde S, Taylor C, et al. Pre-prostatectomy membranous urethral length as a predictive factor of post prostatectomy incontinence requiring surgical intervention with an artificial urinary sphincter or a male sling. Neurourol Urodyn. 2022;41(4):973-9.