Robot-assisted laparoscopic radical prostatectomy (RARP) is enjoying widespread and expanding use for patients with prostate cancer. RARP shows better outcomes in terms of urinary continence as compared with conventional radical prostatectomy. However, some patients suffer prolonged urinary incontinence after RARP and the urinary incontinence interferes with the quality of life in the patients. The pathogenesis of post-prostatectomy incontinence has not been completely elucidated to date. We hypothesized that perioperative clinical parameters including preoperative patient status might affect the severity of post-prostatectomy incontinence. In this study, the relationships between perioperative clinical parameters and post-prostatectomy incontinence were examined to identify risk factors for prolonged severe urinary incontinence.

The subjects were 334 patients who initially underwent RARP between February 2013 and August 2016 at our institute. The patients were divided into a severe urinary incontinence group and a slight or no urinary incontinence group. The severity of urinary incontinence was assessed using a 1-h pad test and the number of pad exchanges per day at 12 months postoperatively. Severe urinary incontinence was defined as when the pad was exchanged more than three times per day or the 1-h pad test was more than 50 g. All patients other than those with severe urinary incontinence belonged to the slight or no urinary incontinence group. The Mann-Whitney U-test was used to examine the relevance of preoperative patient status (age, body mass index (BMI), prostate-specific antigen (PSA), Charlson Comorbidity Index (CCI), and D’Amico risk classification), perioperative parameters (operation time, bleeding, weight of the prostate, posterior reconstruction or not, lymph node dissection or not, nerve preservation or not, preservation of the fascia of the levator ani muscle or not), and pT classification. To confirm the correlations between severe urinary incontinence and the perioperative clinical parameters, multivariate regression analysis was performed. All values are expressed as means ± standard deviation. P-values <0.05 were considered significant.

Of the 334 patients, 299 were evaluable. Twenty-seven patients (9.0%) were in the severe urinary incontinence group, and the remaining 272 patients (91.0%) were in the non-urinary incontinence/slight urinary incontinence group. Mean results of the 1-h pad test in the severe urinary incontinence group and slight or no urinary incontinence group were 65.7±68.3 g and 2.4±5.2 g, respectively. The mean numbers of pads exchanged per day were 2.7±0.5 and 0.5±0.6, respectively. Severe urinary incontinence was significantly correlated with high age (P=0.011), high BMI (P=0.001), lymph node dissection (P=0.003), no preservation of nerves-(P=0.039), no preservation of the fascia of the levator ani muscle (P=0.017), and high-risk group according to the D’Amico risk classification (P=0.010). Multivariate analysis showed that severe urinary incontinence was significantly correlated with high BMI (P=0.009) and the high-risk group according to the D’Amico risk classification (P=0.007)

These results demonstrated that high BMI and the high-risk group according to the D’Amico risk classification contributed to severe urinary incontinence after RARP. It is well known that excess body weight increases abdominal pressure, which in turn increases bladder pressure and urethral mobility, leading to stress urinary incontinence and exacerbation of detrusor instability and overactive bladder. Thus, obesity might also influence urinary incontinence after RARP.
On the other hand, in patients with high-risk prostate cancer, extended resection of the prostate is chosen to achieve radical cure. Extended resection might cause more severe damage to the lower urinary tract, with a risk of prolonged, severe urinary incontinence.

Obesity and extended resection of the prostate to achieve radical cure were risk factors for prolonged severe urinary incontinence after RARP in the present study. Thus, for the patients with obesity and with high risk prostate cancer, sufficient informed consent that prolonged severe urinary incontinence would be occurred in these patients was needed preoperatively.

Haga N et al.Comprehensive approach for post-prostatectomy incontinence in the era of robot-assisted radical prostatectomy. J.Med.Sci.2017;63,46-56.
Kojima Y et al.Urinary incontinence after robot-assisted radical prostatectomy: Pathophysiology and intraoperative techniques to improve surgical outcome. Int.J.Urol.2013;20,1052-1063.