Influence of Demographic and Clinical Factors on Surgical Outcomes of the Transobturator Tape Procedure in Patients with Stress Urinary Incontinence

Stress urinary incontinence (SUI) is defined as the involuntary leakage of urine on effort, exertion, or coughing [1]. The prevalence of SUI increases with age, with a 20-30% rate in young adults, 30-40% in middle age and maximum around 50% after menopause [2]. SUI in most cases is caused by loss of urethral support resulting in hypermobility and lower pressure transmission to the urethra than the bladder. This is surgically curable and many procedures have been introduced for stabilising the bladder neck and/or urethra. Pioneered by Delorme in 2001, the transobturator approach was developed with an aim to reduce the side effects of the retropubic sling procedure such as bladder perforation without entering the space beyond the endopelvic fascia [3]. Parameters such as age, BMI, menopausal status, smoking, history of pelvic surgery (hysterectomy/lower section Caesarean section (LSCS)) and urethral hypermobility are risk factors for stress incontinence and may influence the outcome of transobturator tape (TOT) implantation [4,5].

Chronically increased stress on the pelvic floor is generally regarded as causally related to the increased prevalence of urinary incontinence in obese women as compared to normal-weight women [6]. The influence of obesity on surgical outcomes in SUI patients is still under debate. Obesity may have an impact on the results of the retropubic open or laparoscopic operation for SUI [7]. On the other hand, in the tension-free vaginal tape era, obesity may not influence the outcomes because the procedure is less invasive [8,9,10]. Only few data are available to assess the impact of obesity on the TOT procedure.

It is well demonstrated that the urogenital organs are highly sensitive to the influence of estrogen. In fact, estrogen receptors have been found in the urethra, bladder trigone, round ligaments as well as in the levator ani muscles [11,12]. Following these findings, the idea arose of a possible relation between SUI and the causes of decreased estrogen status, such as menopause.

To date results presented in a number of papers are ambiguous and do not indicate clearly if the above mentioned demographic parameters affect the clinical outcome of midurethral sling surgery. To the best of our knowledge, no study has assessed results after TOT surgery based on presence or absence of history of hysterectomy/LSCS or that of smoking. The purpose of this study was to evaluate the outcome of TOT implantation taking into account the influence of each of these 6 parameters separately and help clarify some of the doubts that exist with regards to the prognostic significance of these different parameters with regards to surgical outcomes after TOT surgery. It is important to understand the significance of these factors to help better manage patients and treatment expectations.

Women presenting with SUI (defined as involuntary leakage during physical activity, coughing or sneezing), underwent a standardized basic office evaluation and were eligible for the study if they had a history of symptoms of SUI for at least 3 months and failure to respond to standard medical treatment and pelvic floor exercises, a post void residual urine (PVRU) volume of less than 150 ml, a negative urinalysis or urine culture, a desire for surgery for SUI, and a positive provocative stress test (defined as an observed transurethral loss of urine that was simultaneous with a cough or Valsalva manoeuvre). A random 150 ml cut off for PVRU was chosen to exclude out patients of voiding dysfunction. The provocative stress test, which had to be positive for inclusion in the study was performed at the time of cystoscopic confirmation for SUI at a volume of approximate 300 ml along with Bonney test. A clinical assessment of urethral mobility (defined as straining angle of 30 degrees or greater relative to the horizontal on the Q-tip test) was also conducted at the same time. For Q-tip test, a sterile lubricated cotton swab was placed into the bladder through the meatus and withdrawn until resistance indicated correct positioning at urethrovesical junction. The angle between the cotton swab at rest and after maximal Valsalva maneuver in degrees was defined as the urethral mobility (measurements were taken using a protractor placed against the patient's perineum).

Exclusion criteria were previous surgery for incontinence, a history of pelvic irradiation, pelvic surgery within the previous 3 months, anterior or apical pelvic-organ prolapse beyond 1 cm proximal to the hymen (Stage II and higher of the pelvic organ prolapse quantitation system) and unfavorable factors on urodynamic testing suggestive of either intrinsic sphincter deficiency or detrusor overactivity. Written informed consent was obtained from each enrolled patient prior to their induction into the study and Ethical committee approval taken.

Finally 50 patients were recruited in the study group, all of whom underwent TOT operation. All the TOT operations done in this study were performed by a single senior surgeon thereby ensuring the same expertise across all cases. All patients across both groups were explained about the possibility of voiding dysfunction postoperatively and the need for clean intermittent self catheterisation.

Data for each patient was collected at first visit and subsequent follow-ups. Information obtained and tests performed at baseline preoperatively were age, weight, height, body mass index (BMI), parity, duration of incontinence, menopausal status, past history of smoking, past history of hysterectomy/LSCS, urethral mobility, PVRU on USG, full bladder and supine empty bladder stress test, and 3 day voiding diary to measure incontinence severity.

Based on age, women were classified into 2 groups: age < 50 and age > 50 years. Patients were considered postmenopausal based on absence of menstrual bleeding for more than 12 months. History of pelvic surgery included caesarean section and hysterectomy. Urethral mobility ≥ 30º on Q-tip test was taken as the criteria for hypermobility. BMI was calculated by dividing the patient's weight by the square of height and women stratified in 2 groups: non-obese group (BMI < 25) and obese group (BMI ≥ 25) [13].

Self-reported measures included the urogenital distress inventory-6 (UDI-6) and the Incontinence Impact Questionnaire-7 (IIQ-7). These 2 tools, UDI-6 and IIQ-7 are shortened versions of the original UDI and IIQ respectively [14,15]. They have shown promise in the assessment of health-related quality of life, symptom distress, and in distinguishing among different types of established urinary incontinence in the clinical setting.

Scoring: Item responses are assigned values of 0 for “not at all,” 1 for “slightly,” 2 for “moderately,” and 3 for “greatly.” The average score of items responded to is calculated. The average, which ranges from 0 to 3, is multiplied by 33 1/3 to put scores on a scale of 0 to 100.

Evaluation for treatment success was done at 6 months and 1 year postoperatively. The primary outcome for treatment success was clinical reduction of complaints as measured with the UDI-6 and IIQ-7 (i.e., a score reduction of 70% or more) and a negative standard volume stress test at 12 months after the onset of treatment. For stress test, a full bladder standing Valsalva and cough manoeuvre was done. If the patient did not leak she was asked to repeat the manoeuvre bending the knees. A post test void of at least 300 ml was necessary for the test to be considered valid. Pre-operative clinical and demographic data were finally correlated with the above treatment outcomes to look for any statistical significance.

The statistical analysis was done using statistical software SPSS for windows (Version 16). Chi-square test was used for non-parametric variables. Student's t test was used for comparing 2 groups and one-way ANOVA test was used for multiple group comparison. P-value < 0.05 was stated as statistically significant.

Data was collected prospectively during the study period of September 2011 to August 2013. Primary outcome data was finally available for 50 women (table 1). The mean age of the whole study group was 49.8 years (range 26-72 years). There were 20 (40%) premenopausal and 30 (60%) postmenopausal patients. None of the postmenopausal patients were using any type of hormone replacement therapy. Mean parity was 2.7 (range 0-6). Average duration of incontinence was 22.9 months (range 9-78 months). Of 50 women 34 (68%) had undergone either hysterectomy or LSCS in the past. Urethral hypermobility defined as Q tip > 30 degree was present in 44 (88%) women. Five patients (10%) had a history of smoking. Of the 50 patients, 24 (48%) were normal-weight women and 26 (52%) were obese women.

We compared outcome success rate by evaluating the success criteria of 70% reduction in UDI and IIQ scores, mean change in these scores at 6, 12 months and provocative stress test at 12 months.

There was a tendency for premenopausal women to have a higher success rate that was statistically significant (each p < 0.05) (table 2). At 6 months, 70% reduction in UDI and IIQ scores was significant in the “premenopausal” group at 95 and 90% respectively compared to only 70 and 53.3% respectively in the “postmenopausal” group (p = 0.005, 0.001). Similarly change in UDI and IIQ scores were -49.2 and -24.9 respectively in the “premenopausal” group compared to -40.8 and -19.1 respectively in the “postmenopausal” group (p = 0.01). At 12 months follow-up, there were mild changes in all outcome variables and p values were similarly significant here for all the treatment outcomes in the 2 evaluation groups. The “premenopausal” group had no positive provocative stress test at 1 year in comparison to 6.7% in the “postmenopausal” group (p < 0.001).

Similarly, statistically significant difference was observed between patients below and at or above 50 years of age in terms of success rate with younger patients faring better (each p < 0.05) (table 3). Past history of hysterectomy/LSCS was associated with poorer treatment outcomes (each p < 0.05 except for positive provocative stress test at 12 months) (table 4). Urethral hypermobility positively influenced the success rate with better outcomes (each p < 0.05) (table 5). On the other hand, history of smoking had no bearing over success rate (each p > 0.05) (table 6). Our results also indicate that there is no statistically significant correlation between BMI and clinical outcomes of sling surgery (each p > 0.05) (table 7).

SUI has been shown to cause deterioration in quality of life, limitations in social relationships, and a higher prevalence of psychological morbidity. It tends to occur mainly because of loss of urethral support with advancing age and with increasing parity. This support can be regained by surgical interventions such as TOT. Multiple factors can affect pelvic relaxation and thereby increase chances of the patient developing SUI. Gürel et al. [16] found that age, marriage period, and parity are directly and strongly related to pelvic relaxation.

It is well known that the prevalence of SUI increases with aging in women owing to menopause and the loss of estrogen. The only study that investigated the relationship between the success of TOT operations and menopause was reported in 2010 by Rechberger et al. [17]. The authors found that the clinical effectiveness of surgical SUI treatment did not depend on the patient's BMI or type of midurethral sling, but that menopausal status and aging significantly influenced the outcome of the surgery. They also concluded that both menopause and aging had a detrimental influence on the final outcome of both the retropubic and transobturator sling procedure. In our study, we confirmed the results of Rechberger et al. [17]. It is well known that estrogen and progesterone receptors have been found throughout the lower urinary tract [11], and many of the tissues involved in female continence have been found to be estrogen-sensitive, such as the urethra and bladder. Because estrogens are also known to have an effect on the synthesis of collagen and the metabolism of collagen in the lower genital tract, the significant difference that we found between pre- and post-menopausal patients is likely related to the loss of estrogen support of urogenital tissues [18].

Higher age has also been described as an important risk factor for developing SUI in previous literature [19,20,21,22]. In a study by Anger et al. [23], at 1 year after surgery, overall outcomes in younger women (aged 65-74 years) were significantly better than in older women (aged > 75 years) with respect to postoperative urge incontinence (20.0 vs. 12.6%), treatment failure (10.5 vs. 7.2%), and outlet obstruction (10.5 vs. 6.6%). They concluded that women aged 75 and older are more likely to experience postoperative urge incontinence, treatment failure, and outlet obstruction after sling surgery.

Obstetric procedures such as hysterectomy/LSCS could increase the risk of SUI by damaging anatomical structures involved in urethral support or the innervation of the urethral sphincter. This damage can be caused by direct surgical trauma or by trauma due to stretching or compression of the tissue [24]. In line with this, our study showed that patients with a prior history of either hysterectomy or LSCS had worse surgical outcomes.

Minaglia et al. [25] and Karateke et al. [26] found that low urethral mobility was associated with higher rates of postoperative incontinence. Paick et al. [27] on the other hand stated that cure rates were not significantly lower in the group without a mobile urethra (< 30º). Theoretically, a successful sling procedure restores continence not by increasing resting urethral pressure but by providing a support the holds the mid-urethra in place while the proximal urethra descends under stress, allowing better pressure transmission and, more importantly, a kinking of urethra during straining [28,29]. When urethra doesn't move well, this kinking does not occur. That's the advocated mechanism for urethral mobility as a prognostic factor. True to this, urethral mobility was found to be an important prognostic factor for TOT surgery in our study.

Studies by Hannestad et al. [30] and Bump et al. [31] have shown the relative risk of SUI to be between 1.8 and 2.92 for current smokers. Whether by direct effect such as bladder irritation or indirectly through smoking-related illnesses that cause increased coughing, such as chronic obstructive pulmonary disease, smoking appears to have a striking causal relationship with SUI. In our study though, no significant differences were seen on comparing the treatment outcomes after surgery in the 2 groups of smokers and non-smokers.

Higher intra-abdominal pressures have been observed in patients with greater BMI, and this may stress the pelvic floor secondary to a chronic state of increased pressure [32]. Increased intra-abdominal pressure elevates pressure at maximum cystometric capacity, and decreases cough pressure transmission from the bladder to the urethra, as well as decreasing Valsava leak point pressure, which may contribute to the development of SUI in obese patients [9]. Obesity-induced neurogenic effects on the pelvic floor may also contribute to the development of urge or urge incontinence [33]. Only 2 studies so far have been reported for the relationship of obesity and TOT outcomes. Rechberger et al. [17] conducted 269 retropubic and 268 transobturator sling procedures and demonstrated that BMI does not influence the clinical effectiveness of SUI treatment. Similarly in the study by Esin et al. [34], there were no significant differences between obese (BMI > 30) and non-obese groups (BMI < 25) in terms of urodynamic parameters, objective cure rate and subjective success, quality of life scores, or postoperative complications. They concluded that BMI does not affect the clinical effectiveness of TOT operation in the treatment of female SUI or mixed urinary incontinence. These findings are consistent with our results. Our study has also revealed that obese SUI patients had no differences in surgical outcomes compared to non-obese patients. TOT surgery can be performed in obese patients with expectations of good treatment outcomes.

In conclusion, the TOT procedure appears to be more effective in premenopausal women, women aged < 50 years, women without history of hysterectomy/LSCS, and presence of urethral hypermobility > 30 degrees. On the other hand, outcomes do not appear to be influenced by the patient's BMI or smoking status. Further prospective, randomized, controlled studies on a larger number of patients are needed to clearly identify factors that would raise the success rate of TOT procedure.