This was a retrospective cohort study of 536 patients who underwent POP surgery from January 2006 to December 2010 enrolled at Yonsei University Severance Hospital. Among them, 228 patients were excluded under the following conditions: having no preoperative UDS, missing any data of UDS parameters and lost during follow-up. Finally 308 patients and their medical records were reviewed and divided into two groups.

Group 1 included 177 patients who were diagnosed with SUI by positive result of preoperative UDS and had a concomitant sling operation such as transobturator tape, tension free vaginal tape (TVT) with POP surgery. Group 2 included 131 patients who were not diagnosed with SUI by negative result of preoperative UDS and therefore did not have a concomitant surgery.

All patients underwent POP surgery such as anterior and posterior repair, perineorrhaphy, abdominal sacrocolpopexy, iliococcygeous hitch with mesh, iliococcygeous uteropexy with mesh, paravaginal repair and iliococcygeous colposuspension, but mainly sacrocolpopexy or colposuspension including anterior and posterior repair. There was no patient who had only posterior repair and perineorrhaphy, which could be less related with unmasking of POP.

There was no significant difference of POP surgical methods between the two groups. All patients were followed at one month, six months and one year. After those follow-up periods, the patients were followed up once a year to evaluate urinary outcomes including de novo SUI, urgency urinary incontinence (UUI) and OAB based on the postoperative subjective symptoms of the patients. OAB was described by urgency, frequency, nocturia and cases that needed medications. And correction failure of SUI was excluded in patients of this study. We defined "de novo" as it resolved after the surgery and appeared newly after one month follow-up.

All 308 patients had preoperative UDS, and we compared 5 parameters of UDS-valsalva leak point pressure (VLPP), maximal urethral closing pressure (MUCP), maximal flow rates (Qmax), detrusor pressure at maximal flow (PdetMax) and maximal cystometric capacity (MCC) to evaluate whether the parameters of preoperative UDS affected postoperative de novo SUI, UUI and OAB.

Statistical analysis was performed with SPSS ver. 18.0 (SPSS Inc., Chicago, IL, USA). Univariate analysis was performed by using Pearson's chi-square test or Fisher's exact test. Logistic regression analysis was performed to determine the significant parameters of UDS affecting postoperative urinary outcomes. Statistical significance was defined as P-value<0.05.

In this study, the prevalence rate of postoperative de novo SUI in group 2 patients who had POP surgery alone was higher than that of group 1 patients who had concomitant surgery, but there was no statistically significant difference. However, higher prevalence rate suggested that concomitant surgery could be related with postoperative de novo SUI.

Yuan et al. [12] reported that POP and SUI shared common pathophysiological etiologies and often coexisted with one another. Then concomitant prophylactic anti-incontinence measures should be taken at the time of POP repair to prevent the postoperative unmasking SUI. In other previous study, the preliminary results of TVT as a prophylactic procedure in clinically continent women with severe prolapse and occult SUI were encouraging. Long-term follow-up was required to confirm the durability of these results [13]. The majority of the previous studies implied that concomitant prophylactic surgery caused better surgical outcomes.

In contrast, there was no statistically significant difference of concomitant surgery according to the study of Borstad et al. [14] but the prevalence of postoperative SUI was less in the group who had concomitant surgery than the group who had no concomitant surgery. However 27% (almost one third) of patients were cured of SUI by prolapse surgery alone, which meant that some preoperative SUI could be corrected by only prolapse surgery.

Some studies showed although concomitant surgery was performed to prevent secondary surgery to repair incontinence, it caused postoperative side effects such as voiding difficulty, bladder outlet obstruction or OAB, so the effectiveness of concomitant surgery and the time of the surgery have been still controversial. One study surveyed the literature to evaluate whether SUI surgery should be performed at the time of POP repair and a surgical algorithm was possible and reported their discussion on this topic at the Incontinence-Research Society (ICI-RS) meeting in 2010. Surgical practice regarding SUI surgery at the time of POP repair varied widely and there was conflicting research articles that supported different approaches. Ongoing trials should provide more information to help construct better algorithms. And other approaches for designing prediction models for this problems might be useful [15]. According to Serati et al. [16], UDS should be considered mandatory for women with POP, especially if scheduled for surgery, since misleading counseling could result in unpleasant and unexpected events. Moreover, in order to validate concomitant surgery on urinary outcomes, it is necessary to compare patients who was performed concomitant surgery with those who was not, if patients were diagnosed as SUI befor surgery. As stated in the study of Latini and Kreder [4], and Reena et al. [5], since POP could mask SUI, SUI might not turn up on UDS, it was necessary to compare patients who had POP and performed concomitant surgery with those was performed only POP surgery regardless of SUI diagnosis. However, since it is hard to find out cases with not performing surgery when patients are diagnosed as SUI, we divided into two groups (one with concomitant surgery and the other with only POP surgery), and figured out the effectivity of concomitant operation in both groups with and without postoperative complications. Focused on the prevalence rate in this study, postoperative urinary outcomes occurred less frequently after concomitant surgery compared with POP surgery alone. But we have some limitations of this study, it were postoperative urinary outcomes based on only subjective symptoms patients had complained during follow-up and POP surgery not assorted. We included all kinds of POP surgery that might affect the surgical outcomes. Therefore we can draw a proper conclusion if we study to build more exact criteria of the postoperative urinary outcomes and with more patients classified by each POP surgery.

Other doctors demonstrated that preoperatively 67.9% of the women in their study were found to have occult SUI in 78 consecutive women were without any symptoms or signs of SUI. Also 64.2% of the women with a positive result to the preoperative Pyridium pad test after pessary insertion were found to have urinary incontinence postoperatively. Therefore preoperative testing is useful to identify women with genitourinary prolapse who have occult SUI and women with a positive result may need a systematic clinical evaluation and urodynamic studies to characterize the incontinence [6].

Indeed, whether urodynamic evaluation has an impact on the choice of, or outcome of surgery still remains controversial. Many studies were conducted on the effectiveness of preoperative UDS parameters, and the patients who had higher preoperative MUCP caused better surgical outcomes. However there was another opinion, they insisted that preoperative UDS parameters were not related with postoperative urinary outcomes [17], and other studies had not shown any difference in surgical outcomes on preoperative UDS parameters [18,19]. And the predictive value of VLPP is inconsistent. Kilicarslan et al. [20] noted that high VLPP was associated with better outcomes, whereas other studies have failed to prove any impacts of preoperative leak point pressures on surgical outcomes [21,22]. Other Korean doctors showed patients with preoperative Qmax<15 mL/sec had a tendency of postoperative voiding dysfunction [23]. Despite conflicting results of many studies, urodynamic study is suggested as the most accurate method for predicting surgical outcomes.

Thus, we compared parameters of preoperative UDS seemed to affect postoperative de novo SUI, UUI, and OAB. The result was that the patients who had postoperative SUI showed statistically higher PdetMax than those who did not and the patients who had postoperative UUI showed statistically lower MUCP than those who did not.

It was difficult to compare about this in each group, because patients with postoperative complications were small in number. We compared preoperative parameters of UDS in patients who had postoperative SUI, UUI, OAB in any surgery. It would be significant in that it was possible to see the preoperative parameters of UDS effective on postoperative complications.

This study has some limitations, we evaluated postoperative de novo SUI, UUI, and OAB based on only subjective symptoms of the patients, and we could not classify mixed form of incontinence and the patients who had symptoms of SUI, UUI, and OAB preoperatively. On the other hand, the strengths of this study were that all surgeries were performed by the same operator and we compared patients with similar POP-quantification stage.

The studies on this topic are ongoing, but still controversial because anatomical defects that cause POP and SUI are so complicated and their etiologies are multifactorial. Therefore, it is difficult to predict surgical outcomes after repair operations. Even though we have some limitations in this study, the effectiveness of concomitant surgery definitely existed in comparison to the prevalence rate. In conclusion, we think more studies with various aspects, objective indicators are warranted to evaluate postoperative urinary outcomes. Also a larger number of patients should be included in future long-term studies to objectively assess the effectiveness of parameters of preoperative UDS and validate concomitant surgery.