Predictive factors for voiding dysfunction after transobturator slings

PURPOSE: To identify the predictive factors for voiding dysfunction after transobturator slings. METHODS: We retrospectively reviewed the records of all patients who underwent a transobturator sling between March 2003 and December 2008. A total of 514 women had available data with at least a six-week follow-up. Patients’ demographics, preoperative symptoms, urodynamic testing including multichannel voiding studies and surgical variables were tabulated. Voiding dysfunction was defined by a catheterized or ultrasonographic postvoid residual greater than 100 cc (≥six weeks after the procedure) associated with any complaints of abnormal voiding. Univariate logistic regression analysis was performed with respect to postoperative voiding dysfunction. RESULTS: The patient population had a mean age of 58.5±12.9 years. Thirty-three out of 514 patients (6.4%) had postoperative voiding dysfunction according to our definition, and 4 (0.78%) required sling transection. No differences were observed between normal and dysfunctional voiders in age, associated prolapse surgery, preoperative postvoid residual, preoperative urinary flow rate, prior pelvic surgery, and menopausal status. Valsalva efforts during the preoperative pressure flow study was the only predictive factor for postoperative voiding dysfunction, 72.4% dysfunctional versus 27.6% normal (p<0.001). CONCLUSION: Preoperative Valsalva maneuver during the micturition could identify those at risk for voiding dysfunction after transobturator sling, and it should be noted during preoperative counseling.


Introduction
Recently, suburethral slings have become the most widely performed surgical procedures for the treatment of stress urinary incontinence.The transobturator (TOT) approach was described in 2001 and has been shown to be a safe surgery with low morbidity and favorable outcomes [1][2][3][4][5] .
Voiding dysfunction after incontinence surgery is a potential complication of all stress incontinence procedures.There are considerable differences in its definitions in the literature; however, most of them use the association of any subjective complaint of abnormal voiding with an objective measure of urinary retention, such as high postvoid residual.Mid-urethral slings are sometimes associated with voiding dysfunction, which can negatively affect a patient's quality of life and satisfaction [3][4][5][6][7] .
Postoperative voiding dysfunction is one of the most frequent complications that require surgical management after sling procedures, and the incidence of reported dysfunction seems to increase with a higher follow-up period 8 .
Identifying preoperative predictive factors for voiding dysfunction is important to advise patients about their individual risks of this complication.Other studies have associated voiding dysfunction after anti-incontinence surgery with increased age, irritable bladder symptoms, pelvic organ prolapse, previous incontinence and/or prolapse surgery, and urodynamic finding of reduced peak voiding flow rates.Very little data is available specifically addressing predictive factors for voiding dysfunction after TOT slings 6,7,[9][10][11][12][13] .
The TOT approach is often chosen over the tensionfree transvaginal tape (TVT) due to lower rates of postoperative voiding dysfunction, therefore it would be useful to stratify which patients would not do well after TOT slings 14,15 .
The aim of this study was to identify predictive factors for voiding dysfunction after TOT slings.

Methods
We retrospectively reviewed the records of all patients who underwent a TOT tape sling at Cleveland Clinic Florida between March 2003 and December 2008.We included people with at least a six-week postoperative follow-up.Institutional Review Board approval was obtained prior to the beginning of study.
Patients were identified from a clinical database and comprised those who underwent a TOT sling peformed alone or in association with reconstructive procedures.All subjects completed a routine questionnaire at all visits, including voiding and incontinence symptoms.Demographics, preoperative symptoms, urodynamics including multichannel voiding studies and surgical variables were analyzed.Urodynamic testing was interpreted by a fellowship-trained urogynecologist, and the voiding curve patterns were reported using standardized terminology: normal, interrupted, low flow, and Valsalva.This terminology refers to pressure-flow graph of urodynamics, in which these micturition aspects can be identified.
TOT slings were performed using a Monarc kit (Americas Medical Systems, Minnetonka, Minnesota, USA) according to the previously described technique by a single attending surgeon who has significant surgical experience with this device 14 .
Only women with complete clinical data were included.Postvoid residual (PVR) was measured (catheterized or ultrasonographically) 6 weeks after surgery.The PVR greater than 100 cc (≥6 weeks after the procedure) associated with any complaint of abnormal voiding was defined as voiding dysfunction.Data were reviewed up to six months after surgery.
Since we were looking for postoperative voiding dysfunction after TOT slings, we excluded all patients with a preoperative PVR higher than 100 cc.Those diagnosed with voiding dysfunction were offered intermittent selfcatheterization and/or physiotherapy.Pharmacotherapy was added at six weeks, and sling transection was offered if they were still symptomatic in the third month in the postoperative period.
All data was anonymous and analyzed using the SPSS software, version 17.0 (SPSS, Chicago, IL).Univariate logistic regression analysis was performed with respect to postoperative voiding dysfunction and possible predictive factors.Descriptive analysis was carried out using frequencies, means, and standard deviations.For comparison between groups, we used the following tests: χ 2 or Fisher's exact for categorical variables and Student's t for independent samples to verify differences between averages.Associations were considered statistically significant if the p-value was lower than 0.05.

Results
The patient population had a mean age of 58.5±12.9 years (range 23.8 to 92.9).They had, on average, complaints of urinary incontinence 5.1 years before treatment and a mean of 2.4 previous vaginal deliveries.Preoperative characteristics of the patients are described in Table 1.
Between March 2003 and December 2008, 514 women were included and had available data with at least a six-week follow-up.We identified 33 out of 514 patients (6.4%) with voiding dysfunction according to our definition.
No differences were noticed between normal and dysfunctional voiders in age, pre-operative PVR, and concomitant prolapse surgery regardless of the treated compartment.Urinary flow rate, prior surgeries and menopausal status were also not predictive of voiding dysfunction in this analysis.Valsalva effort during the preoperative pressure flow study was the only predictive factor for voiding dysfunction.Only 2.4% of patients who did not perform Valsalva maneuver had dysfunctional voiding, while 16.7% of those who did had voiding dysfunction (p<0.05), as seen in Tables 2 and 3.All women who had a postoperative PVR greater than 100 cc complained of abnormal voiding.
None of the enrolled subjects demonstrated elevated detrusor pressure during the preoperative pressure flow studies.We did not uniformly carry out voiding studies postoperatively, therefore we cannot report on voiding parameters in normal versus abnormal voiders postoperatively.
In the voiding dysfunction group, 45.5% (15/33) of the patients improved with Kegel exercises, bladder retraining and self-catheterization by a mean of 16.3 weeks postoperatively.None of the participants underwent sling loosening attempts during the early postoperative phase.A total of 42.4% (14/33) got better using pharmacotherapy (baclofen and benzodiazepines), and 12.1% (4/33) had voiding dysfunction requiring midline transection of the tape in the third month postoperatively.All patients reported normalized voiding and none reported recurrent stress incontinence in the short-term follow-up.

Discussion
Voiding dysfunction after TOT sling procedures is an uncommon complication of this surgery.In our study, the rate was 6.4%, according to our definition.The majority had transient dysfunction, which improved with behavioral or drug therapy (87.9%).Our data allows surgeons to counsel patients that even if they develop dysfunctional voiding after a TOT procedure, there is a low risk of requiring subsequent surgery for tape transection (0.8%).These results confirm previous papers that described voiding dysfunction after TOT sling with the need of sling revision surgery as a rare complication 12,[15][16][17] .
Even though it is rare, voiding dysfunction is the second most common complication that requires surgical intervention according to a study about complications of suburethral slings (the most common was overactive bladder and the third mesh exposure) 8 .This justifies the necessity of predictive factors to provide adequate information to the patient who is a candidate for TOT sling procedures.The most usual surgery performed to address a complication following suburethral sling is the tape incision.It is highly successful in improving voiding dysfunction, but stress incontinence may recur in more than 60% of those patients 18 .
The role of preoperative urodynamic testing is a topic of intense discussion in the Urogynecologic literature.Several papers have indicated that urodynamics may not have value in predicting voiding dysfunction after incontinence surgery, and frequently it would change the surgical plan [19][20][21] .Other researchers have proven the value of urodynamic findings, such as low peak voiding flow rate and detrusor pressure, as predictive factors for the development of voiding dysfunction 7,9,10,13 .Based on the present results, our hypothesis is that women who use a Valsalva maneuver to void may have suboptimal detrusor function, which could lead to the development of voiding dysfunction due to the increased urethral resistance following suburethral sling surgery.
Identifying risk factors associated with postoperative voiding dysfunction can be crucial when choosing a surgical approach for patients with stress incontinence.The urodynamic finding of Valsalva maneuver during the micturition is routinely assessed, readily available and, according to our study, it could identify women at risk for voiding dysfunction after TOT slings.This factor should be noted and considered in the preoperative counseling of patients.

Table 3 .
Voiding dysfunction (numeric variables according to univariate analysis) *p-value calculated by Student's t-test for independent samples; SD: standard deviation; UI: urinary incontinence.

Table 1 .
Demographical and clinical characteristics in the study group