Even in the era of LRP and RALP, urinary incontinence after RP remains a distressing complication that affects postoperative quality of life[5, 7, 11, 12]. The precise etiology of postoperative urinary incontinence is unknown[17, 18]. However, some reports have suggested that selective suture ligation of the DVC should be performed to preserve the rhabdosphincter and underlying neurovascular components, which can improve recovery of urinary continence[17, 19]. Another report revealed that preservation of the lateral aspect of the prostatic fascia contributed to postoperative urinary continence[20]. As shown in these reports, it is important to make efforts to reduce the complication of postoperative urinary incontinence by optimal selection of the surgical procedure. Nevertheless, even when surgeons try to improve the surgical technique to reduce urinary incontinence, a certain probability of postoperative urinary incontinence remains. While most patients with UIIAS will recover their urinary function by one year[2, 3, 9, 10], those patients who do not improve may require additional medical treatment or surgery[21]. Therefore, we need identify the patients at higher risk of postoperative urinary incontinence even one year after surgery from among the patients with UIIAS.
Our results revealed two predictors of urinary function recovery. First, age was an independent predictor of both immediate continence and recovery of urinary continence. According to many previous reports, increased age is related to an increased prevalence of postoperative incontinence[18, 22–24]. The mechanism of age-related postoperative urinary incontinence is not clear[17, 18]. Strasser et al. noted age-dependent decreases in the density of striated muscle cells in necropsies, and concluded that this might be the main reason for the higher incidence of urinary incontinence with increasing age[25]. Other reports have suggested that the natural decrease of rhabdosphincter cells with increasing age underlies the increasing incidence of stress incontinence with age, and that the process could be further accelerated by the surgical trauma of RP[18]. They also speculated that the healing process leading to restitution of normal function is less successful with increasing age. Many clinical and animal studies at the cellular and molecular levels have examined age-related changes and delays in wound healing[26]. In general, age is a risk factor for impaired wound healing. Young people are therefore unlikely to have UIIAS, and even if they do, repair of the sphincter tissue is likely to occur. This is thought to improve urinary function one year after surgery. Our data regarding age and urinary continence are thus supported by evidence from previous reports.
Second, high EBL (≥ 100 ml) at RP was an independent predictor of urinary continence recovery. However, our analyses did not explain the influence between high EBL at RP and immediate urinary continence. In a previous report evaluating the relationship between EBL and postoperative urinary incontinence, there was no effect of blood loss on continence rates at 24 months after surgery[27]. Preisser et al. recently reported on the relationship between EBL during RP and postoperative urinary function. They identified 2,720 patients who underwent RALP between 2009 and 2015, and defined EBL of 150 ml or less as low, EBL exceeding 400 ml as high and 150–400 ml as medium. High EBL was an independent predictor for seven days of incontinence in patients undergoing RALP. However, high EBL at RALP was not an independent predictor of incontinence three months or one year after surgery[28]. They considered that one of the biological reasons for these results is that blood loss is a recoverable factor within normal hematopoietic capacity. In addition, high EBL increases the chance and area of coagulation hemostasis, which can be considered an exacerbating factor in UIIAS. In our data, the first day ULR did not deteriorate even in high EBL patients. In contrast, urinary incontinence improved one year after surgery in high EBL patients, as Preisser et al. also reported. This suggests that urinary continence immediately after surgery may not be negatively affected by high EBL because coagulating hemostasis is kept to a minimum during surgery even if bleeding is observed. And it also suggests that urinary incontinence does not improve even one year after surgery in cases where the amount of EBL is low. Lei et al. reported that the athermal procedure of DVC has a positive effect on postoperative urinary continence[17]. Therefore, it can be said that minimal coagulation hemostasis during surgery can lead to an increase in EBL, but that this has the advantage of improving urinary continence. The results of the present study suggested that urinary continence can be recovered one year after surgery in patients with high EBL due to of recovery of blood loss and minimal coagulation hemostasis.
We did not identify any influence of BMI or prostate volume on postoperative urinary continence. Although some authors reported that lower BMI and smaller prostate volume are associated with better recovery of urinary continence[11, 12], these claims are controversial in terms of the relationship between obesity and urinary incontinence after RP[29]. Another report showed that the influence of prostate volume on continence is very variable[30].
The present study had some limitations. First, this was a single institution study, and the cohort was small. Further studies with larger sample sizes are needed in order to confirm the predictors of urinary function recovery among patients with UIIAS. Second, this study was not conducted as a single-surgeon series. Despite all surgeons using virtually the same techniques, subtle differences in procedure among surgeons might have affected postoperative urinary continence. Third, this was a retrospective study, so we could not analyze possible predictors such as the preoperative urinary condition. In spite of these limitations, we believe that our results indicate that younger age and high EBL at RP are predictors of urinary function recovery among patients with UIIAS.