MRI Membranous Urethral Length Does Not Predict Early Return to Continence Following Robotic-Assisted Radical Prostatectomy
Liz B. Wang, MD, Hersh H. Bendre, BS, David S. Wang, MD, Richard K. Babayan, MD, Boris N. Bloch, MD, Mark H. Katz, MD
Boston Medical Center, Boston, MA
Urinary incontinence following robotic-assisted radical prostatectomy (RARP) is a well-known complication, yet the mechanism of post-RARP incontinence is poorly understood. The urethral sphincter length may be an important predictor of recovery of continence and time to continence. The purpose of this study is to determine if membranous urethral length (MUL), measured via pre-operative T2-weighted magnetic resonance imaging (MRI), can predict time to continence post-RARP.
We performed a single-center retrospective cohort study of patients who underwent a RARP at our institution from 2013 to 2017. A total of 211 patients were identified, of which 101 had a pre-operative MRI. Of the 101 patients, 2 were excluded (lost to follow-up), and the remaining 99 were included.
The definition of continence and time to early continence were analyzed using 2 patient cohorts: Cohort one defined continence as 0 pads and early vs. late continence as ≤ 3 months vs. > 3 months. Cohort two defined continence as 0-1 pads and early vs. late continence as ≤ 2 months vs. > 2 months. Univariate analysis was conducted using analysis of variants (AVONA) for continuous variables and chi-squared test (N > 5) or Fisher’s exact test (N ≤ 5) for categorical variables. Significance was determined with p < 0.05.
For cohort one, continence was achieved in 84 (85%) patients at the most recent follow-up visit. Mean time to continence was 3.93 months. Of the patients who were continent, 38 (45%) patients achieved early continence. Mean MUL was 13.3mm for the early group and 13.7mm for the late group, which was not statistically significant (p = 0.63). On bivariate analysis, smaller prostate size was associated with early return to continence (mean 32.8 grams for early vs. 38.2 grams for late, p = 0.04). Other factors such as age, race, BMI, history of diabetes, MRI findings, intra-operative nerve sparing and lymph node dissection status, total days of post-operative catheter placement, pathologic stage, and Gleason score were also evaluated. On multivariate analysis, none were independently associated with early return to continence.
For cohort two, MUL was again not predictive of early continence (p = 0.960). Higher BMI (p = 0.049) was associated with early return to continence. MRI finding of extension into the seminal vesicles (p = 0.02), and higher pathologic stage (p = 0.015) were both predictive of late return to continence. On multivariate analysis, again, no factors were associated with early return to continence.
The MUL was not a significant predictor of early return to continence after RARP in either cohort. However, smaller prostate size was correlated with early return to continence. Extension of disease into the seminal vesicles and higher pathologic stage may be associated with late return to continence. This knowledge may be useful to clinicians when counseling patients in regards to expectations for return to continence post-operatively.
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