Preoperative Magnetic Resonance Imaging Membranous Urethral Length as a Predictor of Urinary Continence After Radical Prostatectomy: A Systematic Review and Meta-analysis

Abstract

Background and objective: The evidence regarding membranous urethral length (MUL) and urinary continence after radical prostatectomy is inconsistent. The primary objective of this review was to evaluate the association between MUL and postprostatectomy continence.

Methods: Multiple databases were searched up to August 31, 2024. Studies evaluating the association between magnetic resonance imaging (MRI)-measured MUL and urinary continence at 12 mo after prostatectomy were included. Published abstracts were excluded. The pooled association between longer MUL and continence was evaluated using a meta-analysis with random effects. The risk of bias was assessed using Quality In Prognosis Studies (QUIPS) tool. Certainty of evidence was determined using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach (PROSPERO protocol: CRD42023483229).

Key findings and limitations: Thirty studies (11 239 patients) were included. The risk of bias was low in most studies for measurement, confounding, and statistical analysis/reporting. The median MUL between studies ranged from 10.4 to 17.3 mm. Longer MUL (usually dichotomized at the median) was associated with a greater probability of continence (15 studies, 4025 patients; pooled risk ratio [RR] 1.30, 95% confidence interval [CI] 1.18, 1.44; p < 0.0001, I² = 80%). After excluding high risk of bias studies, the association between longer MUL and continence remained significant (pooled RR 1.18, 95% CI 1.08, 1.29; p = 0.003). The certainty of the association between MUL and continence was moderate. No publication bias was evident. The results are limited by a high risk of attrition bias.

Conclusions and clinical implications: Longer preoperative MRI-measured MUL is associated with better urinary continence 12 mo after radical prostatectomy, regardless of the continence definition and assessment method. MUL measurement techniques should be standardized, and MUL should be incorporated in prognostic models.

Keywords: Magnetic resonance imaging; Membranous urethral length; Patient counseling; Prostatectomy; Systematic review; Urinary continence; Urinary incontinence.