INTRODUCTION
Out of 1,000 women, 1.5–1.8 will suffer from pelvic organ prolapse (POP) that necessitates surgery [1]. A woman’s quality of life (QoL) could be greatly impacted by POP. For severe and symptomatic prolapse, surgical repair is the mainstay of treatment, though conservative care is also a possibility. Representative examples of abdominal or vaginal methods to surgically treat POP using mesh include laparoscopic or robot-assisted sacrocolpopexy (LSC or RSC) and transvaginal mesh surgery (TVM). Although RSC is thought to be the best treatment for apical prolapse, it is more expensive and requires more surgical time despite its high success rate and low recurrence rate [2, 3].
Conversely, TVM is considered a less invasive surgical technique that takes less time to complete. After TVM first became available in the 1990s, several studies comparing it with native tissue repair (NTR) demonstrated that TVM is less likely than NTR to cause prolapse recurrence, anatomic failure, and repetitive surgical repair [4-6]. However, TVM has been linked to relatively high rates of bladder damage, mesh exposure, and stress urinary incontinence (SUI) [4, 7]. Nevertheless, our work and other studies indicate that TVM is an excellent technique with favorable outcomes that are not inferior to LSC [8-11].
In addition to POP recurrence and mesh exposure, urinary incontinence is a problematic complication after TVM. In our previous studies and other reports, about 10%−20% of patients after TVM complained of urinary incontinence [8, 12, 13]. Treating all women with a combination of POP and SUI surgery may prevent future SUI procedures, but there is a risk of overtreatment and unnecessary morbidity. Given that surgeons are not always able to predict who would benefit a selective strategy that targets concurrent SUI procedures for women who are at risk of postoperative SUI would be useful. Therefore, a phased approach spares unnecessary surgeries while treating some women with continence surgery secondary to prolapse surgery only when required [14].
Currently, Japan’s only mesh product available for TVM is ORIHIME (Kono Seisakusho), which is made of polytetrafluoroethylene (PTFE), a fluoropolymer (carbon fluoride resin) composed entirely of fluorine and carbon atoms. As it is chemically stable while offering low disintegration and tissue reaction rates, this material has been used in a variety of medical devices including mesh for hernia repair, artificial blood artery repair, sutures, and patches for heart repair [15, 16]. According to one study, it might be safer to utilize PTFE in vivo because PTFE induces less tissue inflammation than polypropylene mesh [17]. As a thin, light, yet strong mesh, ORIHIME can slide off the surrounding tissue; however, we gradually adjusted the mesh length beneath the bladder to range from the cervix to the bladder neck [8].
In the current study, we examined data from patients with POP who underwent TVM using ORIHIME at our institution to identify which factors contribute to postoperative urinary incontinence following TVM using ORIHIME.
MATERIALS AND METHODS
Patients
The medical records of 102 patients who underwent TVM between July 2019 and March 2023 were retrospectively reviewed. Surgical indication was POP of stage ≥2 with symptoms such as sensation of vaginal protrusion or hydronephrosis and/or hydroureter caused by POP even in cases without symptoms.
This study included patients who underwent TVM for POP within the above-mentioned timeframe and excluded those who declined to participate.
The median postoperative observation period was 12.3 months (interquartile range [IQR], 12.1−26.3). The median operative time calculated from all patients was 61.0 minutes (IQR, 54.0−72.3). Table 1 shows clinical data such as age, body mass index (BMI), the presence of diabetes mellitus (DM), POP quantification stage, the types of POP and previous history of hysterectomy, blood loss, operative time, preoperative voiding dysfunction and urinary incontinence, postoperative urinary incontinence, adjustment of mesh length beneath the bladder, or intraoperative complications.
Surgical Methods
The TVM (Uphold-type) method are described in our previous studies [8, 9]. In brief, the process began with hydrodissection. The sacrospinous ligaments were then exposed by entirely dissecting the pubocervical fascia laterally with a blunt technique after the anterior vaginal wall was cut vertically. Subsequently, a skin incision was made 3 cm inferior to the anal center and 4 cm laterally. A Shimada needle threaded with nylon monofilament sutures was then used to further penetrate the sacrospinous ligaments from the incision, aiming for a position 1 or 2 finger breadths medial to the ischial spine. Next, an appropriate shape of ORIHIME (Kono Seisakusho) was cut, spread, and fastened beneath the bladder by removing the mesh arms through the skin incision using nylon monofilament loops. The meshes were cut to fit stencil paper with 2 arms in advance. The arm width was initially set to 4.5−6.0 cm but later increased to approximately 6.0−7.5 cm [8, 9]. The mesh length was adjusted such that it did not drag the bladder neck too much in a cephalad direction by measuring the distance between the cervix or vaginal vault (grasped using Allis forceps) and point Aa, which is 3 cm proximal to or above the hymenal ring [8]. Finally, traction was applied over the externalized arms to ensure correct alignment, and the vaginal wound was closed using 2-0 Vicryl (Johnson and Johnson) sutures.
Assessment Methods of Urinary Incontinence and Voiding Dysfunction
Postoperative urinary incontinence, whether urge or stress, was defined as a severe interruption to patients’ daily life because of incontinence according to our previous reports [8, 9]. We purposely defined voiding difficulty as a residual urine volume of 100 mL or more. In fact, the volume of the postvoid residual urine of ≥100 mL was defined as voiding dysfunction in earlier reports [18, 19].
Statistical Analysis
The Pearson chi-square test was conducted to evaluate the correlation between preoperative plus intraoperative factors and postoperative urinary incontinence. The multiple logistic regression model and the Cox proportional hazards model were used to determine independent factors that contribute to postoperative urinary incontinence. Statistical analysis was performed using JMP PRO ver. 17 (SAS institute Inc.). A P-value <0.05 was considered statistically significant.
RESULTS
Table 1 shows the patient background. Intraoperative peritoneal injury was observed in 2 patients; however, there were no serious postoperative complications noted. Clavien-Dindo classification grade I was assigned to both [20].
The correlation analysis between pre- and intraoperative factors and urinary incontinence revealed that the presence of DM and the adjustment of the mesh length beneath the bladder were significantly associated with postoperative urinary incontinence (both P<0.05) (Table 2). Furthermore, independent factors influencing postoperative urinary incontinence were identified using multivariate logistic regression analysis. In the univariate and multivariate analyses, the presence of DM and the adjustment of the mesh length beneath the bladder were significant predictors among pre- and intraoperative factors (P=0.010, P=0.013, respectively) (Table 3).
The univariate Cox proportional hazards model indicated that patients with DM and those treated with ORIHIME mesh length adjusted beneath the bladder had significantly higher risks of postoperative urine incontinence (P=0.024, P=0.044). The multivariate analysis revealed that the independent predictors linked to a shorter time to postoperative urinary incontinence were the presence of DM (hazard ratio [HR], 4.99; 95% confidence interval [CI], 1.69−14.72; P=0.004) and the adjustment of the mesh length beneath the bladder (HR, 6.63; 95% CI, 1.44−30.57; P=0.015) among pre- and intraoperative factors (Table 4).
The Kaplan-Meier curves and the log-rank test results showed significant differences in the postoperative urinary incontinence-free survival rates of patients with and without DM, and patients treated with and without ORIHIME mesh length adjustment (P=0.016, P=0.027, respectively) (Fig. 1A, B).
DISCUSSION
We could not be sure whether preoperative urinary incontinence was masked by POP, but the presence or absence of preoperative urinary incontinence is also shown in Table 1. Of the 14 patients with postoperative urinary incontinence, 8 patients with pure SUI or mixed urinary incontinence with SUI predominance that interferes with their daily lives underwent midurethral sling surgery because behavioral therapy and medication were no longer effective. The presence of DM and the adjustment of the mesh length beneath the bladder significantly correlated with the occurrence of postoperative urinary incontinence in the correlation analysis (Table 2), and multiple logistic regression analysis as well as Cox proportional hazards model showed that the presence of DM and the adjustment of the mesh length beneath the bladder were independent factors for postoperative urinary incontinence in both multivariate analyses (Tables 3 and 4). The Kaplan-Meier curves with log-rank test also showed a significant difference between patients with or without DM, and those treated with or without ORIHIME mesh length adjustment beneath the bladder (Fig. 1). Although the presence of DM cannot be controlled, this study suggests that adjusting mesh length beneath the bladder can reduce urinary incontinence after TVM.
In April 2019, the U.S. Food and Drug Administration issued an order to all manufacturers to stop selling synthetic mesh intended for transvaginal repair of anterior compartment prolapse because the manufacturers had not proven the safety and effectiveness of these devices [21]. However, in Japan, TVM has been shown to have effective outcomes such as a low rate of mesh-related problems like urinary incontinence as well as a low rate of prolapse recurrence following surgery [9, 22, 23]. Additionally, the QoL of patients undergoing TVM notably improved [9, 23, 24]. A minimal mesh method has previously been recommended to treat POP [23]; however, based on our earlier research, we recommend TVM using ORIHIME with wide arms and adjusted length beneath the bladder [8, 9].
SUI may improve following POP surgery, but the procedure may also reveal SUI that was previously hidden by POP [25]. Preoperative urodynamic investigations are helpful in assessing de novo SUI, but the assessment of SUI that appears on stress testing with repaired organ prolapse cannot predict all SUI [26]. Several studies looked for predictors of de novo SUI to assess whether concurrent anti-incontinence surgery was required; postoperative SUI in women with POP and SUI (occult or symptomatic) may be lowered by concomitant midurethral sling surgery [27]. However, if necessary, postponing the midurethral sling surgery and conducting a 2-stage surgery after POP repair should be considered for the patient with a high need for incontinence-preventing surgery [27]. One possible risk factor for the development of de novo SUI is excessive tension on the bladder neck after mesh fixation, which changes the urethral morphology [8, 28]. We recommend concurrent midurethral sling surgery only for high-risk women who would most benefit from reduced postoperative SUI.
Such a decision should be made considering the findings of a sufficient preoperative evaluation to avoid overtreatment. Furthermore, preoperative decision-making requires a solid foundation based on individual risk prediction. According to several studies [29-31], TVM, age, and BMI could possibly predict SUI. Earlier studies indicated that the TVM group had a higher incidence of SUI than the LSC or RSC group did [2, 10]. However, our novel method described previously may be able to reduce the incidence of postoperative urinary incontinence by preventing excessive mesh tension on the bladder neck [8]. The higher incidence of postoperative urinary incontinence in the group in which the mesh length beneath the bladder was not adjusted is consistent with several studies suggesting that postoperative SUI is caused by neural denervation, urethral supporting deficiencies, and overcorrection of the bladder neck [32-34].
There are various limitations to this study. First, this is a single-center retrospective study. Second, the patient population is relatively small. Third, the median follow-up period after surgery was rather short. We understand that a more thorough, future investigation including several institutions could increase the data’s generalizability and provide more conclusive evidence based on these findings to gain consensus over these limitations. Larger sample sizes in future studies will further increase the statistical power and robustness of the results, and longer observation spans may further support the validity and long-term reliability of the study’s findings. Given these limitations, we believe that we must continue to implement TVM that does not lead to recurrence.
In conclusion, adjustment of mesh length beneath the bladder could prevent postoperative urinary incontinence. In TVM using ORIHIME, the size of mesh should be adjusted based on the length from the cervix to the bladder neck.
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