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The purpose of our study was to evaluate the influence of obesity on clinical characteristics, quality of life (QoL), and outcomes in patients with stress urinary incontinence (SUI) who underwent the transobturator tape (TOT) surgery.
The medical records of SUI patients who underwent the TOT operation from January 2007 to February 2009 were retrospectively reviewed. Patients with any neurologic diseases that affect the voiding pattern were excluded, and 107 patients were enrolled. The patients were divided into nonobese (BMI<25) and obese (BMI≥25) groups. The preoperative evaluation consisted of history taking, physical examination, cystometrography, 3-day frequency-volume chart, King's Health Questionnaire (KHQ), and symptom perception scale questionnaires.
The nonobese group consisted of 55 (51.4%) patients and the obese group of 52 (48.6%). The median age was 49.0 (range, 30.8-73.5) years in the nonobese group and 52.7 (range, 35.5-73.5) years in the obese group (p>0.05). The obese group showed a higher SUI symptom grade, urethral hypermobility, urgency, and urge incontinence scale than did the nonobese group (each p<0.05). Neither the domains of the KHQ nor the items on the 3-day frequency-volume chart differed between the two groups (each p>0.05). After the operation, the symptom scales and parameters in the 3-day frequency-volume chart of the obese group were similar to those of the nonobese group (each p>0.05). The objective success, recurrence, and complication rates at 1year were similar in the two groups (each p>0.05).
Obese SUI patients had worse SUI symptom grade, urgency, and urge incontinence symptoms than did nonobese patients. However, surgical correction by the TOT operation could restore the symptoms and voiding parameters as effectively in obese patients as in nonobese patients.
Stress urinary incontinence (SUI) is the most prevalent disease in middle-aged women, with an incidence of 30% to 50%. Obesity is one of the important risk factors for the development of urinary incontinence with old age, in addition to vaginal delivery, history of gynecological surgery, body mass index, menopausal status, smoking, and coffee and alcohol consumption [1,2]. Some authors have described an increase of intra-abdominal pressure in obese patients , and this phenomenon may stress the pelvic floor, possibly causing nerve and muscular injury that might lead to a higher prevalence of SUI . Also, increased body mass index (BMI) is known to be associated with urge and mixed urinary incontinence . However, not all SUI cases are associated with obesity thus, the clinical characteristics and urodynamic parameters might differ between obese and nonobese SUI patients.
The influence of obesity on surgical outcomes in SUI patients is still under debate. In the past, obesity may have had an impact on the results of the retropubic open or laparoscopic operation for SUI . In the tension-free vaginal tape (TVT) era, on the other hand, obesity may not influence the outcomes because the procedure is less invasive [4,7-9]. However, obesity may be associated with a high incidence of postoperative urge incontinence after the TVT procedure .
Although the transobturator tape (TOT) procedure launched by Delorme  became a mainstay of SUI operation because of a high success rate and low risk of bladder perforation, only few data are available to assess the impact of obesity on the TOT procedure. Therefore, we investigated the influence of obesity on clinical characteristics, quality of life (QoL), and outcomes in patients with SUI who underwent the TOT surgery.
The medical records of SUI patients who underwent the TOT operation from January 2007 to February 2009 were retrospectively reviewed. Patients who had any possible conditions that might affect urinary function, such as neurologic disease, urinary tract infection, or urolithiasis, were excluded. A total of 107 patients were enrolled.
Body weight and height were measured in the hospital, and BMI was calculated by dividing the patient's weight by the square of height. Women were classified in two groups: nonobese group (BMI<25) and obese group (BMI≥25). The severity of urinary incontinence was classified by using the Stamey grade, including grade I for women who lose urine only with coughing, sneezing, or lifting heavy objects; grade II for those who lose urine with minimal activities such as walking or arising from the sitting position; and grade III for those who are totally incontinent in the upright position (11).
The operation was carried out with the outside-in obturator tape (Iris-TOT, Dow Medical). The procedure was carried out in the usual manner with the patient under intravenous propofol infusion with local infiltration of bupivacaine. General or spinal anesthesia was performed when the patient refused the intravenous anesthesia. A Foley catheter was removed the next morning. A total of 3 (5.8%) and 2 (3.8%) patients in the obese group underwent cystocele and cystorectocele repair, respectively, and 3 (5.5%) patients in the nonobese group underwent cystocele repair during the TOT operation.
All patients were evaluated by history taking such as the severity of urinary incontinence, parity, pelvic organ surgery history, and bladder irritative symptoms. For health-related QoL assessments, the patients were asked to fill out the King's Health Questionnaire (KHQ). The questionnaire was scored according to the method of Okamura et al . Also, a physical examination, 3-day frequency-volume chart, and urodynamic study were performed on all patients to gather information about urethral hypermobility, cystocele grade according to Pelvic Organ Prolapse Quantification (POPQ), Valsalva leak point pressure (VLPP), and detrusor overactivity. Urethral hypermobility was defined as a straining angle of 30 degrees or greater relative to the horizontal on the Q-tip test, and intrinsic urethral sphincter deficiency as VLPP under 60 cmH2O. Detrusor overactivity was defined as any involuntary detrusor contractions during the filling phase. To evaluate the patient's irritative bladder symptoms, the frequency, urgency, and urge incontinence perception scale questionnaire were completed (Appendix).
The 3-day frequency-volume chart and physical examination were completed again 4 to 6 weeks after the operation, and patients were considered subjectively cured, improved, failed, or recurred according to their reports at 12 months by response to a phone or mail interview.
Statistical analysis was performed by using the Mann-Whitney U-test for parametric continuous variables and linear-by-linear association or Fisher exact test for nonparametric variables. The statistical program used was the Statistical Package for Social Sciences, version 12.0 software (SPSS, Chicago, IL, USA). A p-value <0.05 was considered statistically significant.
Of the 107 patients, 55 (51.4%) were normal-weight women and 52 (48.6%) were obese women (Table 1). The median age of the nonobese group was 49.0 (range, 30.8-73.5) years and that of the obese group was 52.7 (range, 35.5-73.5) years (p>0.05). Obese patients showed a higher severity grade of urinary incontinence than did the nonobese group (89.1% grade I, 9.1% grade II, and 1.8% grade III in the nonobese group, and 65.4% grade I, 30.8% grade II, and 3.8% grade III in the obese group, p=0.007). In the nonobese group, the SUI classification was pure SUI, mixed SUI with stress dominant, and mixed SUI with urge dominant in 25 (45.5%), 30 (54.5%),and 0 cases, respectively, whereas in the obese group, the classification was 16 (30.8%), 34 (65.4%), and 2 (3.8%) cases, respectively. Although the mixed type was more frequent in the obese group, there wasnot a significant difference (p=0.066). Urethral hypermobility was observed more frequently in obese patients than in nonobese [31 (59.6%) vs 22 (40%), p=0.034]. However, there were no significant differences in any of the 9 domains of the KHQ (Table 2) or in the incidence of intrinsic urethral sphincter deficiency and detrusor overactivity between the two groups.
On the 3-day frequency-volume chart, obese patients tended to void more frequently than nonobese patients, but the difference was not significant (9.93±2.46 vs 8.98±2.78 per day, p=0.072). No differences in nocturia or functional bladder capacity were found between the two groups (each p>0.05) (Table 3). Obese patients had worse preoperative urge and urge incontinence perception scale scores than did nonobese patients (p=0.043, p=0.003, respectively) (Table 4). However, the differences disappeared after surgery.
The overall subjective cure, improvement, fail, and recurrence rates were 85.5%, 7.3%, 3.6%, and 3.6% in the nonobese group, and 86.5%, 3.8%, 3.8%, and 5.8% in the obese group, respectively (p>0.05) (Table 1).
De novo urgency was observed in 2 (3.6%) patients in the nonobese group and 4 (7.7%) patients in the obese group (p>0.05). The number of patients who had taken anticholinergics postoperatively because of urinary frequency or urgency symptoms that were sustained even after the operation was 11 (20.0%) and 6 (11.5%) in the nonobese and obese group, respectively (p>0.05). Five patients in each group complained of a slow urine stream after the operation, but all were improved with urethral dilatation. We observed no cases of urinary retention or blood transfusion.
The present study has revealed that obese SUI patients had a worse grade of SUI and worseurge and urge incontinence perception scales than did the nonobese group, whereas no differences were found in surgical outcomes, recurrence rates, or complications.
Although obesity is a well-established risk factor for the development of SUI, and could impact the voiding pattern, the exact mechanism is not clear. 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 . 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 VLPP, which may contribute to the development of SUI in obese patients . Obesity-induced neurogenic effects on the pelvic floor may also contribute to the development of urge or urge incontinence . Our data showed that obese patients had a worse grade of SUI and worse urgency and urge incontinence perception scales than did nonobese patients, which is consistent with previous studies. In contrast with previous reports, however, we found no differences in VLPP (data not shown) or the incidence of intrinsic urethral sphincter dysfunction between the obese and the nonobese group. We believe that obesity was defined by a BMI of 30 or greater in the Western population-studied in the previous report, and this might make a difference in the results. In a Korean population study, Ku et al demonstrated no difference in VLPP , which agrees with our data. However, unlike our results, they reported that obesity was not associated with the severity of SUI or degree of Q-tip test. We think that these differences are caused by their use of the Ingelman-Sundberg SUI severity scale and degree of Q-tip itself, unlike the 30 degree criteria used in our study.
Although our study did not demonstrate a difference in QoL between the obese and the nonobese group, Richter et al reported that obese SUI patients had a higher mean Urogenital Distress Inventory (UDI) score and Incontinence Impact Questionnaire (IIQ) score . This discrepancy can be explained by the use of different instrument and analysis methods to assess QoL.
There have been a number of reports about the success rate of TVT surgery in obese patients, and the consensus is that obesity does not influence the outcomes of TVT [4,7-9]. So far, however, only one study has been reported for the relationship of obesity and TOT outcomes. Rechberger et al conducted 269 retropubic and 268 transobturator sling procedures and demonstrated that BMI does not influence the clinical effectiveness of SUI treatment . However, they did not assess voiding symptoms, and we believe that the retropubic approach may have a greater chance of de novo urgency. This was confirmed by Sung et al. They performed a meta-analysis of TVT and transobturator approach studies and concluded that the transobturator sling operation had a lower risk (odds ratio:0.54) of de novo bladder voiding symptoms than did the TVT procedure . Consistent with the previous study, our data revealed that only 2 (3.6%) patients in the nonobese group and 4 (7.7%) in the obese group complained of de novo urgency, with no significant difference between the groups.
In our study, overall outcomes and recurrence rates were checked by response to phone and mail interviews conducted 1 year after surgery, and no significant differences were found between the two groups. However, Hellberg et al performed 970 cases of TVT sling with a median 5.7-year long-term follow-up, and reported a significant difference in the failure rate in obese patients (BMI> 35) . Therefore, to evaluate the exact influence of obesity on TOT outcomes, long-term follow-up is needed.
Obese SUI patients had a worse grade of SUI, worseurgency and urge incontinence perception scales, and a higher incidence of urethral hypermobility than did nonobese SUI patients. However, QoL by the KHQ, the incidence of intrinsic urethral sphincter deficiency, outcomes, the recurrence rate, and complications of the TOT procedure did not differ significantly between the groups. The results of this study suggest that the TOT operation can be applied even in obese SUI patients with high expectations, although longer-term follow-up is needed.
The perception scales for measuring patient's bothersomeness about urinary frequency, urgency and urge incontinence.
This work was supported by Chungbuk National University Grant in 2008. 2010