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Logo of injInternational Neurourology JournalThis ArticleAims and ScopeInstructions for Authorse-Submission
 
Int Neurourol J. 2010 April; 14(1): 26–33.
Published online 2010 April 30. doi:  10.5213/inj.2010.14.1.26
PMCID: PMC2989485

Predictors of Postoperative Voiding Dysfunction following Transobsturator Sling Procedures in Patients with Stress Urinary Incontinence

Abstract

Purpose

We evaluated the influence of preoperative physical examination (PE) and urodynamic study (UDS) findings on objective postoperative bladder emptying, the subjective development of bladder storage symptoms, and patient-reported success of correction of stress urinary incontinence (SUI).

Materials and Methods

From January 2007 to August 2008, a total of 159 female patients with SUI underwent transobturator midurethral sling surgery (TOT). The patients were selected for SUI, with no overactive bladder (OAB) symptoms, no detrusor overactivity (DO) on UDS, no pelvic organ prolapse, and no history of prior anti-incontinence surgery. Of these patients, 128 patients (aged 38-74 years; mean age, 51.8±7.1 years) with follow-up of at least 12 months were included in the analysis. All patients had PE and UDS findings, including Q-tip testing, free maximal flow rates (Qmax), filling cystometry, Valsalva leak point pressure, detrusor pressure at maximal flow, and maximal urethral closing pressure. The primary outcome was postoperative voiding dysfunction, defined as the subjective feeling of not empting one's bladder completely and a postvoid residual ≥100 ml. A secondary outcome, "cure" of SUI, was defined as "a negative result on the cough stress test and no subjective complaint of urine leakage." We analyzed the preoperative parameters by univariate and multivariate regression for voiding dysfunction, de novo OAB, cure rate, and the patients' satisfaction.

Results

Patients with a preoperative Qmax < 15 ml/s (7 patients) had a tendency for postoperative voiding dysfunction compared with those with a Qmax 15 ml/s (15 patients) (35.0% vs. 13.9%, respectively; p=0.046). No other preoperative parameters had a statistically significant influence on postoperative voiding dysfunction. Receiver operating characteristic (ROC) analysis revealed that Qmax was a good predictor because the area under the ROC curve value of Qmax was 0.81 (95% CI: 0.73 to 0.89, p<0.001). The univariate and multivariate analysis of the preoperative PE and UDS parameters demonstrated that no significant differences and no independent risk factors were related to the postoperative de novo OAB, cure rate, or the patients' satisfaction.

Conclusions

These findings suggest that preoperative UDS results, especially Qmax, could be used to predict postoperative voiding dysfunction after the TOT procedure.

Keywords: Urinary Incontinence, Treatment outcome, Urodynamics

Introduction

Stress urinary incontinence (SUI) may have a considerable impact on personal lifestyle and health-related quality of life. Midurethral sling surgery has become the mainstay of female SUI treatment because of its efficacy and low complication rates [1]. However, the value of various preoperative physical examination (PE) and urodynamic study (UDS) parameters in predicting the postoperative "success" of the midurethral sling surgery for the treatment of SUI is still controversial [2].

The effect of midurethral sling surgery on the postoperative voiding function (storage and emptying) of the patient is a major consideration, along with correction of the SUI, in determining success or failure. The midurethral sling provides dynamic kinking of the urethra not when abdominal pressures are at the resting phase but when they increase. Theoretically, then, the midurethral sling does not cause voiding dysfunction including weak stream, hesitancy, or straining [3]. However, postoperative voiding dysfunction, such as a decreased free maximal flow rate (Qmax) or increased postvoid residual (PVR) volumes, has been reported after midurethral sling surgery [4].

In this observational, retrospective study in a selected homogeneous patient group, we evaluated the preoperative PE and UDS findings that might affect objective postoperative bladder emptying, the subjective development of voiding symptoms, and patient-reported success for correction of female SUI.

Materials and Methods

From January 2007 to August 2008, 159 female patients with SUI underwent transobturator midurethral sling (TOT) surgery and were available for follow-up at 12 months. Of these patients, 128 patients (aged 38-74 years; mean age, 51.8±7.1 years) with follow-up of at least 12 months were included in the analysis (see exclusion criteria below).

The preoperative workup included a medical history PE, including Q-tip testing, Pelvic Organ Prolapse Quantification (POP-Q), 1-hour pad test, and 3-day frequency-volume chart, and UDS evaluation (Urolab® System V, Life-Tech, USA), including free Qmax, PVR volumes, filling cystometry (CMG), Valsalva leak point pressure (VLPP), detrusor pressure at maximal flow (PdetQmax), and maximal urethral closing pressure (MUCP). Stamey's definition was used to grade the severity of SUI [5]. Q-tip testing was performed in the lithotomy position, and UDS was performed in the sitting position by using a 6 Fr dual-lumen catheter and a 9 Fr rectal balloon catheter with a medium filling rate. Free Qmax was performed when the patients' voided volumes were more than 150 ml. Data were interpreted according to the International Continence Society (ICS) guidelines [6]. Exclusion criteria included patients who had 1) a preoperative predominant complaint of urge incontinence, 2) detrusor overactivity on CMG, 3) PVR greater than 100 ml, 4) genital prolapse greater than stage I (POP-Q), and 5) previous anti-incontinence surgery.

All enrolled patients underwent the TOT procedure with the Monarc® Subfascial Hammock System (American Medical Systems, Minnetonka, MN, USA) by the same operatorunder spinal or general anesthesia according to the patient'sand surgeon's preference. The surgical procedure was carried out as described by Mellier et al [7]. A urinary catheter was inserted after the operation and was usually removed after 24 hours. After urinary catheter removal, the patients were evaluated for flow rate and PVR volumes (Biocon-500™, M-cube Technology). Patients remained hospitalized until a PVR <100 ml was obtained. When difficulty with bladder emptying persisted, the patients were taught to self-catheterize before being discharged. The patients were followed after discharge at 1 week, 1 month, 3 months, and 12 months. To assess the voiding functions associated with surgery, the patients were asked whether their voiding had changed after surgery, and uroflowmetry and PVR measurement were compared objectively. At the 1-year follow-up, the patients were evaluated for surgical results, patient satisfaction, and long-term complications.

Postoperative voiding dysfunction was defined as subjective voiding symptoms (weak stream, residual urine sensation, and voiding difficulty) with PVR 100 ml, and postoperative de novo OAB wasdefined as de novo urgency or urge incontinence. Surgical success ("cure" of SUI) was defined as anabsence of any subjective complaint of urinary leakage during stressful activities and absent objective leakage on stress testing. Improvement was defined subjectively as a significant reduction of urine leakage, such that it did not require further treatment. All other outcomes were regarded as failures [5]. The stress cough test was performed with the patient in the standing position with a full bladder. The patients' perception of satisfaction was categorized as "very satisfied," "satisfied," "so-so," or "dissatisfied," with both very satisfied and satisfied considered as satisfaction [8]. Statistical analyses were performed with SPSS (Windows version 13.0; SPSS, Chicago, IL, USA).

Univariate analysis was performed by using Pearson's chi-squared or Fisher's exact tests and Student's t-test. Multivariate analysis was performed by means of logistic regression analysis to determine the predictive factors affecting postoperative voiding dysfunction, de novo OAB, the cure rates, and the patients' satisfaction. Receiver operating characteristic (ROC) curve analysis was used for each independent variable to determine their predictive ability in the detection of postoperative voiding dysfunction and de novo OAB. Statistical significance was defined as p<0.05.

Results

A total of 128 patients were included in the analysis. The patients' mean age was 51.8 years (range, 38-74 years). Patient characteristics and preoperative UDS study parameters are summarized in Table 1. The grade of symptoms of 72 (56.3%) patients was I, that of 45 (35.2%) patients was II, and that of 11 (8.6%) patients was III. There were no serious intraoperative complications, such as bladder perforation, wound infection, or significant vessel injury. There were no patients with chronic urinary retention following the procedure. The longest period of intermittent catheterization was 5 days, and no patient required urethrolysis.

Table 1
Characteristics of the patients

Twenty-two (17.2%) patients complained of postoperative voiding dysfunction and 19 patients (14.8%) complained of de novo OAB, respectively. Eighty-nine (69.5%) patients were cured and 31 (24.2%) were improved. One hundred six (82.8%) patients were satisfied with the TOT operation.

The univariate analysis of the preoperative UDS parameters demonstrated that Qmax was associated with postoperative voiding dysfunction. The postoperative voiding dysfunctionwas significantly higher in the group of women with Qmax < 15 ml/s (7 patients) than in those with Qmax 15 ml/s (15 patients) (35.0% vs. 13.9%, respectively; p=0.046). There was no significant difference in postoperative voiding dysfunction between women with PdetQmax < 20 cmH2O (5 patients) and those with PdetQmax 20 cmH2O (17 patients) (20.0% vs. 16.5%, respectively; p=0.768 Figure 1). The multivariate analysis indicated that Qmax was the only factor related independently to the postoperative voiding dysfunction (p<0.001, odds ratio=1.17), but other parameters were not significant. ROC analysis revealed that Qmax was a good predictor because the area under the ROC curve (AUC) value of Qmax was 0.81 (95% CI: 0.73 to 0.89, p<0.001). In contrast, the AUC of PdetQmax was 0.52 (95% CI: 0.39 to 0.65, p=0.76), which indicated that PdetQmax was an appropriate predictor. The cutoff value for Qmax <14 cmH2O was the most predictive of postoperative voiding dysfunction, with a sensitivity of 91.5% and a specificity of 31.8% (Figure 2).

Figure 1
Results of comparing preoperative parameters including maximal free flow (Qmax), detrusor pressure at maximal flow (PdetQmax) in patient with postoperative voiding dysfunction (PVD).
Figure 2
Receiver operating character (ROC) curve analysis. The area under the ROC curve (AUC) value of Qmax was 0.81 (95% CI 0.73 to 0.89, p<0.001) and the AUC of PdetQmax was 0.52 (95% CI 0.39 to 0.65, p=0.76), respectively.

The univariate and multivariate analysis of the preoperative PE and UDS parameters demonstrated no significant differences and that no independent risk factors were related to the postoperative de novo OAB, cure rate, or the patients' satisfaction (Tables 2, ,33).

Table 2
Multivariate analysis for predictive factor for postoperative voiding dysfunction and de novo OAB
Table 3
Multivariate analysis for cure of USI and the patients' satisfaction

Discussion

In this study, we demonstrated an association between Qmax and postoperative voiding dysfunction. Qmax < 15 ml/s was well correlated with postoperative voiding dysfunction. No relationship was demonstrated between other preoperative PE and UDS parameters and postoperative voiding dysfunction.

The effect of preoperative urodynamic study parameters on postoperative voiding dysfunction after anti-incontinence surgery has been assessed in several studies. Lemack et al reported that of a total of 655 consecutive women, who underwent Burch colposuspension or pubovaginal sling surgery, postoperative voiding dysfunction developed in 57, including 8 in the Burch colposuspension group and 49 in the pubovaginal sling group. No preoperative urodynamic study findings were associated with an increased risk of voiding dysfunction in any group, and mean Qmax values were similar among women with voiding dysfunction and those without voiding dysfunction [9]. However, Salin et al reported that 20 patients (20%) showed evidence of voiding dysfunction after the tension-free vaginal tape (TVT) procedure, and age (p<0.038) and preoperative Qmax (p<0.001) were independent risk factors for voiding dysfunction [4]. Another recent study found that of 625 women who underwent various midurethral sling procedures (TVT, TVT-obturator, TOT, or TVT-secure), 163 (26%) patients showed postoperative voiding dysfunction, and Qmax was the only independent risk factor for postoperative voiding dysfunction [3].

Our study utilized a selected patient population with SUI without prolapse, in the absence of any symptoms of OAB or findings of DO on UDS, who underwent the TOT procedure with the Monarc system by the same operator. The outcomes in this report were based on the number of patients who had postoperative voiding dysfunction, which was determined by the criteria of postoperative voiding symptoms and PVR 100 ml, and postoperative de novo OAB, which was determined by de novo development of any subjective OAB symptoms. In addition, surgical outcomes were evaluated by subjective complaint of urinary leakage and the cough stress test with a full bladder. Inclusion criteria were selected to obtain a more homogeneous group on which to base our conclusions. Patients with preoperative symptoms of OAB or DO on UDS were excluded in order to more accurately observe the development of de novo OAB symptoms. Patients with vaginal prolapse greater than stage I (POP-Q) or a history of prior anti-incontinence surgery were also excluded for accurate assessment of postoperative voiding dysfunction.

Our findings suggest that Qmax < 15 ml/s is the value most predictive of the development of postoperative voiding dysfunction and that the effects of other UDS parameters on postoperative emptying or de novo OAB symptoms were not statistically significant. From a clinical standpoint, it is important to recognize that these findings do not imply that postoperative voiding dysfunction does not exist in patients with Qmax 15 ml/s (13.9% incidence) or that all patients with Qmax < 15 ml/s (35% incidence) will have symptomatic complaints. It is somewhat intuitive that a lower preoperative Qmax may predispose to decreased postoperative emptying.

Historically, preoperative parameters have not been predictive of the result of anti-incontinence surgery [2,10,11]. Most preoperative parameters have been taken from the PE and UDS findings [12,13]. Many authors who have reported on which preoperative parameters can influence the outcome of surgery have included patients with mixed incontinence, who have OAB symptoms preoperatively. Voiding dysfunction after the midurethral sling procedure was reported by Wang et al [14]. They concluded that an abnormal uroflow pattern and configuration were the only urodynamic study parameters predictive of postoperative abnormal voiding. In addition, they suggested that the severity of intrinsic sphincter deficiency (ISD) was not correlated with voiding dysfunction after the midurethral sling operation. They concluded that tension-free placement of the tape may not prevent the development of postoperative voiding dysfunction [14]. According to our data, slow uroflow can predict the postoperative voiding pattern. However, we did not evaluate the uroflow pattern. We agree with Wang et al that the severity of ISD had no correlation with postoperative voiding dysfunction.

The Q-tip test has been utilized and analyzed for the determination of urethral hypermobility. It has been suggested that 30 degrees of movement can be used to delineate urethral hypermobility. Bakas et al concluded that adequate mobility of the proximal urethra is associated with a high success rate of the midurethral sling procedure [15]. Fritel et al also reported that urethral mobility has predictive value for SUI in women [16]. However, the Q-tip test was not a predictor of the postoperative subjectivesuccess or failure in our data. Fritel et al also concluded that mixed incontinence, OAB, and MUCP had no significant prognostic value [16]. Other authors have supported their opinion that the midurethral sling operation is a highly successful treatment even with ISD [11,17]. However, Paick et al reported that the patients with low a VLPP had a lower cure rate [18]. We agree that ISD does not predict the success or failure of surgical treatment of SUI.

Deval et al reported that the subjective cure rate wassignificantly lower in patients who underwent the procedure under general or spinal anesthesia [19]. However, there was the opposite opinion that the type of anesthesia did not influence the result of surgical treatment [20]. Our data showed that the anesthesia types did not affect the voiding function or the cure rate (Tables 2 and and33).

Conclusions

Patients with Qmax < 15 ml/s have a higher probability of postoperative voiding dysfunction. The other preoperative PE and UDS parameters, including Q-tip degree, VLPP, MUCP, and PdetQmax, did not predict postoperative voiding dysfunction.

These findings suggest that preoperative UDS results, especially Qmax, could be used to predict postoperative voiding dysfunction after the TOT procedure, which may help to inform clinicians of proper surgical candidates.

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