Several RCTs have been conducted to compare the TVT and pubovaginal sling as treatments for SUI. Bai et al showed that the rectal fascia pubovaginal sling outperformed both TVT and Burch colposuspension, with 92.8% of the patients experiencing cure at the 12-month follow-up, compared with 87.8% of the Burch colposuspension group and 87% of TVT patients [8]. Wadie et al reported similar continence rates between TVT (92%) and the pubovaginal sling (92%) [9]. According to meta-analyses, TVT and pubovaginal slings showed similar continence rates [odds ratio (OR): 0.82; 95% confidence interval (CI): 0.42-1.59; p=0.55] [10]. RCTs comparing TVT with other MUS procedure are listed in Table 2.

The largest trial was recently published by Meschia et al, who reported outcomes on 190 patients randomly assigned 1:1 to TVT or IVS [12]. The study showed significantly higher continence rates for patients treated with TVT, regardless of the applied definition of continence. TVT outperformed IVS, considering the success rates evaluated according to any definition of continence (OR: 0.51; 95% CI: 0.31-0.83; p=0.007) and the presence of a negative stress test (OR: 0.47; 95% CI: 0.28-0.82; p=0.007). The subjective cure rates were not different (OR: 0.63; 95% CI: 0.37-1.09; p=0.10) [10]. A comparative study between TVT and SPARC reported similar continence rates in the two arms (87.1% vs. 80.7%) and similar complication rates across all the assessable parameters [13].

When comparing the TVT procedure to the TVT-O procedure, Laurikainen et al reported that the objective cure rates, defined as negative cough stress test at 2 months postoperatively, were 98.5% for the TVT group and 95.4% for the TVT-O group [16]. Subjective cure rates as demonstrated by improvement on questionnaire scores were similarly high in both groups.

Lee et al randomly assigned 120 women to the TVT or TVT-O procedures [17]. The only significant differences between the groups were the mean operative time (TVT, 15.2 min; TVT-O, 11.5 min) and sling length used (TVT, 23.1 cm; TVT-O, 16.1 cm). The rates of cure (TVT, 86.8%; TVT-O, 86.8%), improvement (TVT, 6.6%; TVT-O, 8.2%) and failure (TVT, 6.6%; TVT-O, 5.0%) were similar.

A meta analysis by Latthe et al that compiled data from all available RCTs between retro pubic and trans-obturator slings showed similar subjective cure rates between the groups [18]. These data indicate little clinical difference between the retro pubic and trans-obturator approaches (Table 2).

A prospective study to compare the efficacy and safety of the 'inside-out' (TVT-O) and 'outside-in' (TOT) trans-obturator tape procedures reported that TVT-O and TOT showed similar cure rates (86% vs. 92%) [19]. Approximately 1 year after surgery, parameters in the incontinence quality of life (I-QoL) questionnaire improved significantly in both groups, but there was no statistical difference between the groups. Patients satisfaction rates with TVT-O and TOT (96% vs. 98%) were similar (Table 3).

Debodinance conducted a prospective comparative study of 100 SUI patients: 50 TVT-O vs. 50 Monarc [20]. The cure rate at 1 year was 94% in the TVT-O group vs. 90% in the Monarc group.

Lee et al performed a prospective, multicenter randomized comparative study between the U-type and H-type TVT-SECUR procedures (Table 4) [21]. The overall objective cure rate was 83.9% (239 of 285): 87.5% (126 of 144) for the U-type vs. 80.1% (113 of 141) for the H-type (p=0.091). The overall subjective cure rate was 76.4% (217 of 284): 77.1% (111 of 144) for the U-type vs. 75.7% (106 of 140) for the H-type (p=0.786). Improvement in the I-QoL and domain scores of the International Consultation on Incontinence Questionnaire-Female Lower Urinary Tract Symptoms (filling and incontinence sum, QoL score) questionnaires and patients satisfaction favored the U-type method.

Meschia et al reported that the TVT-SECUR procedure was effective for the treatment of primary SUI with 78% and 81% subjective and objective cure rates, respectively. No significant differences were seen in success rates when the tape was inserted by either the U- or H-type method [22]. The TVT-SECUR procedure appears to be an effective treatment for women with primary SUI, with an overall success rate of 80%.

If patients show detrusor underactivity during preoperative uroflowmetry or urodynamics, we cannot expect successful surgical outcomes after MUS. There is a delicate balance after MUS implant between continence and obstruction, and it is difficult to estimate the optimal degree of tension to be applied during surgery, especially in case of detrusor underactivity. If the tape is too loose, incontinence may persist. On the other hand, if the tape is too tight, urinary obstruction could result. Between 0% and 13% complete urinary retention occurs following the TOT procedure [23,24], and tape sectioning or tape adjustment are necessary in up to 5% of the cases [6].

The adjustable MUS has been shown to allow adjustment of tension for a number of days after surgical intervention, thus permitting correction of postoperative incontinence or obstruction [25]. Maroto et al performed the trans-obturator adjustable tape procedure in 77 patients [26]. A total of 69 patients (90%) were objectively continent, 5 (6.5%) had considerable improvement, and in 3 patients (3.5%), the treatment failed. Additional pelvic floor surgery did not have any significant influence (p=0.519), neither did the need for adjustment (p=0.323).

While surgical correction of SUI is associated with good long-term success rates, urgency urinary incontinence (UUI), as an independent entity and as a co-factor in patients with SUI, remains difficult to treat. Whereas patients with mixed urinary incontinence (MUI) undergo anti-incontinence procedures mainly to control predominantly stress-related symptoms, there are unresolved issues about the effect of pre-existing urgency symptoms on postsurgical outcomes, and what mechanisms may underlie any postoperative symptom changes.

A few studies have suggested that UUI may improve after the TVT procedure. Rezapour and Ulmsten reported that not only SUI but also UUI was cured in 85% of the patients and significantly improved in 4% [27]. Segal et al reported that the improvement rate of the irritative subscales on the Urinary Distress Inventory (UDI) for patients with MUI was 87.8% [28]. Paick et al evaluated the outcome at least 6 months after the TVT, SPARC, and TOT procedures in women with MUI [29]. The cure rates in women with MUI were similar following the TVT, SPARC, and TOT procedures (for SUI: TVT, 95.8%; SPARC, 90.0%; TOT, 94.0%; p=0.625, and for UUI: TVT, 81.9%; SPARC, 86.4%; TOT, 82.0%; p=0.965). Low maximum urethral closure pressure and the presence of uninhibited detrusor contraction during cystometry were deemed independent risk factors for UUI treatment failure.

Although the development of trans-obturator tapes or single-incision slings may limit the rate of bladder perforation, urethral or vaginal perforation is another cause of concern regarding this approach. In a meta-analysis of randomized controlled trials comparing complications after MUS procedures, retro pubic approaches caused up to a 24% risk of bladder perforation [31]. According to the devices, trends were identified in favor of TVT for causing bladder perforations, compared with IVS and SPARC. When compared with the retro pubic and trans-obturator approaches, bladder perforation (OR: 2.33; 95% CI: 1.26-4.32; p=0.007) was significantly less common in the patients treated by trans-obturator tapes (Table 5). In a recent study on TVT-SECUR, lateral vaginal wall perforation was found in 2.1% (3/141) of women treated with the hammock approach [21]. Neuman reported a 4% incidence of vaginal perforation in their first 100 cases [35]. The TVT-SECUR system requires a wider tunnel to prevent dragging of the vaginal submucosal connective tissue and perforation of the vaginal mucosa when placing the end of the device into the fibrous tissue of the internal obturator muscle.

Although the complications of bladder and vaginal erosion are well recognized, these complications are inadequately reported in the literature [31]. In a trial conducted in the United Kingdom and Ireland, 175 patients underwent TVT placement, of whom 6 had a tape-related complication within 5 years (erosion into the vagina, obstructed voiding, suprapubic extrusion, or erosion into the bladder), and some presented between 2 and 5 years postoperatively [36]. A further patient presented with vaginal erosion due to TVT placement after 5 years of follow-up and was not included in the 5-year data. Overall, urethral erosion gives a risk of tape-related complications of 4.6% (8/175). The true value may be higher, however, because the full study population has not been surveyed beyond 5 years postoperatively.

The recently published study by Meschia et al reported that vaginal erosion was significantly more common after IVS than after TVT (IVS, 9%; TVT, 0%; p=0.009) [12]. In a meta-analysis, the rate of tape erosion was lower in patients who underwent TVT, although only a nonsignificant trend was observed (OR: 0.26; 95% CI: 0.06-1.03; p=0.06) [31]. The incidence of vaginal erosion following retro pubic and trans-obturator tape insertion was similar.

A multi-institutional study compared obstructive voiding complications between the retro pubic and trans-obturator procedures [37]. Obstructive complications were significantly higher in the retro pubic group (retro pubic, 18.3%; trans-obturator, 11.0%). Minassian et al compared the incidence of voiding dysfunction, defined as urinary retention or post-void residual (PVR) >200 ml at discharge, among women after three types of anti-incontinence procedures: 63 TVT, 42 Burch colposuspension, and 33 suburethral sling [38]. The incidences were 50%, 15%, and 24%, respectively.

Previous studies have shown associated voiding dysfunction following TVT (range, 4.3-10%) [39,40], as well as de novo overactivity (range, 6-15%) [41,42]. Voiding dysfunction after MUS can also be related to the pre-existing urgency symptom, de novo urgency. According to a study on postoperative urgency treatment, of the 59 patients with pre-existing urgency, 54.2%, 35.6%, and 39.0% demonstrated symptom persistence at postoperative 1, 6, and 12 months, respectively [43]. Of the 32 patients without preoperative urgency, 3.1% and 18.8% of patients demonstrated de novo urgency at 1 and 6 months, respectively, but symptom persistence to 12 months was observed in 6.2%. Overall, urgency lasting 12 months was observed in 25 (27.5%) of the entire cohort.

Groin pain following the trans-obturator procedure is a troublesome complication, for both patients and surgeons. Laurikainen et al randomly assigned 267 patients to TVT or TVT-O and reported that postoperative groin pain was significantly more common in the TVT-O group than in the TVT group (16% vs. 1.5%, respectively, p<0.001) [16]. In addition, patients in the TVT-O group had significantly longer hospital stays and needed significantly more postoperative opiate analgesia than did the patients in the TVT group. They also reported a single case of retropubic hematoma after TVT and urinary tract infections (TVT, 8%; TVT-O, 13%).

Liapis et al reported the outcome of TVT in 32 women with failed MUS, showing an objective cure rate of 77% and a subjective cure rate of 71% with a mean follow-up of 18.6 months [44]. In conclusion, they stated that patients who showed recurrent SUI and who had adequate urethral mobility might be candidates for TVT repair. A retrospective study with 29 women who underwent repeat MUS due to persistent or recurrent SUI found that the cure rate was 75.9%, with a mean follow-up of 18.1 months after repeat MUS [45]. In addition, the study also showed that the approach of repeat surgery can affect the outcomes when choosing MUS to salvage a failed sling. The cure rate was lower in women who received trans-obturator slings (62.5%) than in women who received retro pubic slings (92.3%) after repeat MUS. Although the cohort of the study was too small to make a meaningful comparison, other studies also showed a lower cure rate of the trans-obturator approach as a repeat MUS procedure compared with the retro pubic approach [46,47]. A possible explanation for the difference in the cure rate of repeat retro pubic and trans-obturator procedures is the angle of the tape supporting the mid-urethra. The retro pubic sling has a U shape, which may be more supportive and obstructive than the trans-obturator modifications. Another explanation is that the approach from outside the trans-obturator procedure requires wider dissection of the periurethral area, which may cause migration of the tape.

Anti-incontinence procedures may yield a fixed, scarred urethra, which leads to lower success rates, as seen in patients with intrinsic sphincter deficiency (ISD) and those with no urethral hypermobility. Liapis et al showed a lower success rate (30%) among women with a fixed urethra [48]. Although it is difficult to compare the success rates due to differing primary procedures (e.g., pubovaginal sling, collagen, MUS), the critical risk factor for failure that has been suggested in some studies is a fixed urethra [27,49-52]. Several studies have also looked at pubovaginal slings in the treatment of recurrent SUI with success rates of 50% to 90% [53-55]. Although the use of pubovaginal slings in women who have failed MUS procedures has not been studied, a pubovaginal sling may offer more advantages in women who have a scarred, less mobile urethra and with more severe degrees of ISD.

A peri-urethral injection in patients with a failed sling has shown good clinical efficacy when used to salvage failed anti-incontinence procedures [56]. Of the 5 patients with failure in the study, peri-urethral injections resulted in cure in 3 patients and improvement in 1.

Voiding dysfunction after a sling procedure may be due to urethral obstruction from hyper-elevation of the bladder neck or an exaggerated kink in the urethra. These symptoms could be obstructive (hesitancy, slow stream, intermittency, feeling of incomplete voiding, need to strain or void in the half-standing position) or irritative (pain, frequency, dysuria, nocturia, urgency, urge incontinence). A detailed clinical history is elemental in the detection of urinary symptoms suggestive of infravesical obstruction. The most important aspect of the history is to ascertain the absence of obstructive symptoms before the sling procedure. Abdominal and vaginal examinations should be performed to evaluate the presence of scars, erosions, residual bladder neck mobility, and associated prolapse. The presence of exaggerated urethral or urethrovesical junction angulation with a high, fixed urethra located in the retro pubic area is suggestive of urethral hypercorrection [57]. Although there is no established cutoff between normal and abnormal PVR, and no evidence of correlation between PVR and symptoms of obstructive voiding, PVR of more than 100 ml is considered abnormal in women [58-60]. Blaivas and Groutz proposed an obstruction nomogram for women on the basis of free maximal flow rate and maximal detrusor pressure during pressure-flow study [61]. The nomogram characterizes patients into four categories: no obstruction, mild obstruction, moderate obstruction, and severe obstruction. Massolt et al compared obstructive symptoms according to a standardized questionnaire with the Blaivas-Groutz nomogram and found no correlation between the severity of symptoms and the degree of obstruction related to the four nomogram categories [62]. Occasionally, cystourethroscopy may be indicated to rule out an eroded tape or tumors in the urethra or bladder [57].

In summary, there is no specific investigation to confirm obstruction in patients. The diagnosis relies on several parameters that must confirm clinical suspicion. The history of initial symptoms following MUS procedure, low peak flow rate, high voiding pressure, significant PVR, and abnormal urethral calibrating must all be considered for a conclusive diagnosis of urethral obstruction.

The initial management of a patient after a MUS procedure should place her in one of the two following categories: acute complete urinary retention or chronic urinary retention with obstructive voiding dysfunction. If the patient is in the first category, a voiding trial should be performed within 48-72 hours following surgery. However, if the patient presents with signs and symptoms of dysfunctional obstructive voiding indicative of chronic urinary retention, the approach may vary. In an Australasian survey that included 74 respondents who had performed 1,549 polypropylene sling procedures (TVT or suprapubic arc sling), 95 cases (6.5%) of urinary retention were reported [63]. Most were managed conservatively by clean intermittent self-catheterization (38%) or indwelling urethral catheterization (35%). Thirty-three women required operative management by sling division (20%), early sling loosening by traction (7%), and urethrolysis with sling removal (7%). A combination of initial conservative management followed by surgery was needed in 7 patients (7%).

A multi-institutional review of 241 women who had undergone the TVT procedure revealed 47 women who developed urinary retention for more than 24 hours. Of these women, 68% experienced resolution of urinary retention in the first 48 hours after surgery and 11% were managed with intermittent catheterization or an indwelling Foley catheter [64]. The remaining patients underwent different treatments: 7 had tape release and 3 had tape incision. There is no consensus on the appropriate surgical revision techniques. Tape release, urethrolysis, and sling incision can be options as surgical treatment for voiding dysfunction after MUS.

The rate of recurrent SUI after surgical treatment of urethral obstruction was reported to be up to 36%, except in a study with 2 patients [65]. Table 6 summarizes case series reporting the surgical management of urinary retention after sling procedures.

Another important issue is the optimal time for further treatment, such as anti-muscarinic agents in cases where urgency is present postoperatively. A study evaluating the optimal time for overactive bladder symptoms after MUS recommended treatment if urgency is noted at 1 month postoperatively in patients with pre-existing urgency and after 6 months for those without preoperative urgency [39].