Postoperative membranous urethral length and continence recovery after robot-assisted radical prostatectomy: a Bayesian longitudinal meta-analysis

Postoperative magnetic resonance imaging (MRI)-measured membranous urethral length (MUL) may reflect the functional urethral substrate preserved after robot-assisted radical prostatectomy (RARP). We aimed to characterise how postoperative MUL influences the likelihood and timing of urinary continence recovery after RARP. This PROSPERO-registered review (CRD420261518338) searched PubMed, Embase, Web of Science, and CENTRAL. Eligible cohort studies assessed postoperative MRI-measured MUL and urinary continence after RARP. Continence outcomes were synthesised using Bayesian longitudinal meta-regression. Time-specific continence probabilities, odds ratios per MUL increment, and modelled time to 50% continence probability were estimated. Risk of bias and evidence certainty were assessed using QUIPS and GRADE. Eight cohorts comprising 938 patients were included. At a reference postoperative MUL of 13.52 mm, modelled continence probabilities were 26.4%, 57.8%, 76.1%, and 88.1% at 1, 3, 6, and 12 months, respectively. Per-millimetre odds ratios for continence were 1.31 (95% credible interval [CrI] 1.04-1.67) at 1 month and 1.55 (1.21-2.03) at 12 months. Modelled time to 50% cohort-level continence probability was 2.32 months (95% CrI 1.12-4.71) at the reference MUL and a 1-mm increase was associated with a 22.3% (7.9-35.9%) shorter time.Excluding one influential study attenuated the association, with CrIs crossing 1. The overall certainty of evidence was rated as low. Longer postoperative MUL was associated with greater modelled continence probability and earlier modelled recovery. Prospective validation of the incremental predictive value of postoperative MUL beyond established predictors is required to justify routine postoperative MRI or guide individual prognostication.