To assess preoperative anatomical parameters associated with early recovery of urinary continence (UC) following robot-assisted radical prostatectomy (RARP).

A prospective cohort study was carried out on patients who underwent RARP for clinically localised prostate cancer at Sydney Local Health District, Australia between January 2017 and January 2020. All patients underwent pre-operative assessment including transperineal ultrasound (TPUS), computed tomography (CT) and magnetic resonance imaging (MRI). Patient demographic and clinicopathological data were also collected prospectively. Membranous urethral length (MUL) measurements at rest and during pelvic floor contraction were collected as part of functional pelvic floor assessment with TPUS. Pelvic dimensions and inner pelvic volume was measured based on CT and MRI using previously described methods (Kaufmann et al). “Early” recovery period was defined as three months following RARP and UC was evaluated at six weeks and three months using EPIC questionnaire. Complete UC was defined as zero pad or one safety pad with pad weight of <20g/24 hours.

142 patients underwent RARP during the study period and their clinicopathological data is summarised in table 1. Complete UC was achieved in 30 (21.1%) at six weeks and 36 (26.4%) at three months. In the multivariate binary logistic regression analysis, younger age (OR 0.899, CI 0.828-0.976, P=0.012), higher prostate volume to inner pelvic volume ratio (OR 1.231, CI 1.047-1.448, P=0.012) and negative margin (OR 0.899, CI 0.828-0.976, P=0.012) were independent predictors of recovery of UC at six weeks but not at three months. Overall, anatomical variables such as MUL at rest or pelvic parameters did not correlate with UC recovery during the early postoperative period. However, longer MUL at pelvic contraction (P=0.033) and narrow interspinous length (0.014) were independent predictors of lower pad weight at six weeks on multivariable linear regression analysis. Smaller prostate volume (P=0.001), low pelvic height (P=0.014) and wider transverse inlet length (P=0.032) were independent predictors of less pad number usage at three months on multivariate analysis.

Recovery of UC post RARP may be influenced by various anatomical, technical and functional factors. Parameters such as prostate size and MUL have been identified to affect UC at >12 months after RARP. Our results demonstrate higher prostate volume to inner pelvic volume ratio and longer MUL positively impacts recovery of UC at the very early postoperative phase following RARP while a smaller prostate volume, lower pelvic height with wider transverse inlet length predicted less pad number usage at three months. These anatomical parameters can be determined based on routine preoperative imaging modalities and can be utilised to develop a preoperative risk assessment tool which may allow clinicians to provide tailored preoperative counseling and optimise individual patient’s postoperative UC management.

In patients who underwent RARP, anatomical determinants of early postoperative UC recovery included higher prostate to inner pelvic volume ratio, MUL during pelvic floor contraction, and various pelvic dimensions obtained through routine preoperative imaging assessments.

Kaufmann, D., Lauscher, J., Grone J., zur HAusen, G., et al. CT-based measurement of the inner pelvic volume. Acta Radiol. 2017 Feb;58(2):218-223.