Abstract
AIMS
This study examined the association between the need for a repeat voiding trial after midurethral sling (MUS) surgery and 1-year success rates.
METHODS
We conducted this secondary analysis of the participants in the Urinary Incontinence Treatment Network Trial Of Midurethral Sling (TOMUS) study which compared retropubic vs. transobturator MUS. A standard voiding trial was attempted on all subjects. The ‘repeat voiding trial’ group included subjects discharged with catheterization. All others were considered ‘self voiding’. Success rates between the groups at 1 year were compared, followed by multivariate analyses controlling for previously reported clinical predictors of success.
RESULTS
Most women (76%) were self-voiding, while 24% required a repeat voiding trial. The objective success rate at 1 year was 85.8% in the repeat voiding trial group and 75.3% in the self-voiding group (p=0.01). Subjective success rate at 1 year was 61.0% in the repeat voiding trial group and 55.1% in the self-voiding group (p=0.23). Women in the repeat voiding trial group continued to demonstrate greater objective success than the self-voiding group in multivariate analysis that controlled for previous incontinence surgery, pad weight, urethral mobility, urge score and type of MUS (p=0.04, OR 1.82, 95% CI 1.03-3.22).
CONCLUSIONS
Women who require a repeat voiding trial following MUS surgery have greater objective success at 1 year postoperatively when compared to those who are self-voiding at the time of discharge. These results may help reassure women who require catheterization after MUS surgery that their outcome is not compromised by this immediate transient postoperative result.
Keywords: Stress Urinary Incontinence, Voiding Dysfunction, Midurethral Sling
Introduction
Postoperative voiding trials have commonly been used to predict voiding efficiency and incomplete bladder emptying after surgery for incontinence or prolapse, [1, 2] with their “failure” often translating into a need for postoperative urinary catheter drainage or intermittent self-catheterization. The prospect of being discharged home with either alternative can often trigger anxiety, may increase the risk of infection, incite concern for needing further surgery (involving either urethrolysis or sling release), and can impact patient satisfaction with the procedure.
In a multicenter, randomized equivalence trial that compared the outcomes of retropubic and transobturator midurethral slings (TOMUS), incomplete bladder emptying (defined as a post-void residual of greater than 100 cc after a retrograde fill of 300 cc) at the time of discharge was common, but of short duration [3]. 19% (114/597) of patients were managed with an indwelling urethral catheter and 5% (29/597) were managed with intermittent catheterization[4]. Two weeks after surgery, 6% (38/597) reported any catheter use, and by six weeks, only 2% (9/597) reported any catheter use[4].
The initial transient inability to pass a voiding trial and the need for repeat testing may represent a proxy for increased tensioning of the sling though it is not known if this leads to better results for patients. In a study of Burch colposuspension and pubovaginal slings successful subjects had higher voiding pressures implying “a little tension is a good thing”[5]. However, this finding was not reproduced in a study of midurethral sling procedures [6]. In fact there were no changes in urodynamic parameters which correlated highly with either subjective or objective success. It is unclear whether the need for a repeat post-operative voiding trial ultimately predicts successful surgical outcome of the procedure.
The primary objective of this study was to examine the association between the need for a repeat voiding trial after mid-urethral sling surgery and 1-year objective and subjective success rates. A secondary objective of this study was to determine whether there were differences in preoperative and postoperative urodynamic voiding measures that were different in these two groups.
Materials and Methods
We conducted a secondary analysis of the participants in the Urinary Incontinence Treatment Network (UITN) Trial Of Midurethral Sling (TOMUS) study, which randomized 597 women to retropubic versus transobturator midurethral sling (MUS). The primary purpose of this trial was to compare both objective and subjective cure rates between each type of MUS. The design and primary results of the TOMUS trial have been published previously[3, 7]. To determine the need for continued catheterization postoperatively, on the day of discharge, (either postoperative day 0 or 1) a standardized voiding trial was performed on all subjects who did not have a surgical bladder perforation. The day of discharge was typically day 0 for subjects who only had a MUS, and day 1 for subjects who had concomitant procedures. Subjects had their bladders retrograde filled to 300mL or to bladder capacity, whichever was less. The catheter was removed, the subjects voided within 10 minutes and this voided volume was measured. The post void residual (PVR) was calculated by subtraction of the voided volume from the fill volume. If the subject voided greater than 10 minutes after the retrograde fill, or if the voided volume was more than 50mL greater than the fill volume, the subject was catheterized for the PVR. A subject was deemed to be “self-voiding” if their PVR was less than or equal to 100mL and if it was less than one third of the total bladder volume, otherwise they were sent home with a catheter or having been taught intermittent self-catheterization. In our analysis, this population that was sent home requiring catheterization was defined as the “repeat voiding trial” group. An interim voiding trial conducted in the same way as the postoperative voiding trial was then performed for these subjects 1 to 3 days later.
Preoperative and postoperative (12 months) non-instrumented uroflowmetry (NIF) and pressure flow studies (PFS) were performed in the TOMUS trial, according to International Continence Society Guidelines [8] and according to a standardized, previously published research protocol [9]. In subjects with valid and plausible pre and postoperative NIF and PFS studies, changes in urodynamic measures from preop to postop were compared in the repeat voiding trial group and the self–voiding group excluding those few subjects who ultimately required sling release.
TOMUS outcomes were assessed at 1 year. Objective treatment success was met if the subject had a negative standardized stress test, a negative pad test (defined as <15 mL of urine leakage over 24 hours) and no retreatment for SUI. Retreatment could include anti-incontinence surgery, treatment with a device, periurethral bulking agents, medication, or behavioral treatment. Subjective treatment success was defined as no self-reported leakage on a 3-day voiding diary, no self-reported stress-type UI symptoms (MESA questionnaire responses must be ‘rarely’ or ‘never’ for each stress-type symptom) and no retreatment for SUI as defined in objective success. Subjects who had both objective and subjective success were considered the “subjective and objective success” category.
Univariate logistic regression analyses were conducted with 95% confidence intervals to determine the association between need for repeat voiding trial and the three definitions of success, 1) objective success, 2) subjective success, and 3) subjective and objective success. The univariate analysis was then repeated excluding those subjects who ultimately required sling release to achieve self-voiding. We then performed a multivariate logistic regression analyses controlling for previously reported clinical predictors of objective and subjective success [10]. These predictors included previous incontinence surgery, pad weight, urethral mobility and urge score. To ensure that any results were not dependent on the type of sling performed, we also controlled for the type of MUS. Descriptive statistics on change in urodynamic study (UDS) measures by voiding trial results were reported as the mean and standard deviation. Linear models were fit to assess change in UDS measures by voiding trial groups. A 5% two-sided significance level was used for all statistical testing. All analyses were performed using SAS (version 9.3, SAS Institute, Cary NC, USA).
Results
Table I displays the baseline characteristics of the TOMUS study population. Seventy-six percent (454/597) women were self-voiding at the time of discharge and 143 (24%) required a repeat voiding trial. Most of the women who required a repeat voiding trial had spontaneous improvement in voiding with time; after surgery, only 6% (38/597) and 2% (9/597) reported any catheter use at 2 and 6 weeks, respectively [4].
Table I.
Demographic, Anthropometric, and Clinical Characteristics of the Study Population*
| Characteristics | All Patients (N= 597) |
|---|---|
| Age- yr | 52.9 ±11.0 |
| Race or ethnic group- no. (%)‡ | |
| Hispanic | 71 (11.9) |
| Non-Hispanic white | 473 (79.2) |
| Non-Hispanic black | 17 (2.9) |
| Non-Hispanic other | 36 (6.0) |
| Body-mass index§ | 30.3 ± 6.7 |
| No. of vaginal deliveries — no. (%) | |
| 0 | 70 (11.7) |
| 1 or 2 | 291 (48.7) |
| ≥3 | 236 (39.5) |
| Previous surgery for urinary incontinence — no./total no. (%) | 79/595 (13) |
| Previous surgery for prolapse — no./total no. (%) | 23/595 (4) |
| Postmenopausal — no./total no. (%) | 415/595 (70) |
| Current hormone-replacement therapy — no./total no. (%) | 171/595 (29) |
| Quality-of-life measures | |
| Urogenital Distress Inventory score¶ | 134.6 ± 45.5 |
| Incontinence Impact Questionnaire score" | 151.5 ± 97.4 |
| Pad-test weight — g | |
| Median (10th–90th percentile) | 12.5 (3.6–89.0) |
| Incontinence episodes — no./day | |
| Median (10th–90th percentile) | 2.7 (0.7–6.7) |
| Urinary-incontinence symptom score** | |
| Stress score | 19.3 ± 4.6 |
| Urge score | 6.3 ± 4.0 |
Plus–minus values are means ±SD. Percentages may not total 100 because of rounding. Data on pad-test weight were available for 594 women; data on incontinence episodes per day for 593 women.
Race or ethnic group was self-reported.
The body-mass index is the weight in kilograms divided by the square of the height in meters.
Scores on the Urogenital Distress Inventory range from 0 to 300, with higher scores indicating greater distress.
Scores on the Incontinence Impact Questionnaire range from 0 to 400, with higher scores indicating more negative effect on quality of life.[11]
Symptom scores are the sum of responses from nine questions regarding stress symptoms (with scores ranging from 0 to 27 and higher scores indicating greater severity) and six questions regarding urge symptoms (with scores ranging from 0 to 18 and higher scores indicating greater severity), adapted from the Medical, Epidemiological, and Social Aspects of Aging questionnaire.[12]
Objective data at one year was collected on 559 women, 425 self-voiders and 134 repeat voiding trial subjects. The objective success rate at 1 year was 85.8% in the repeat voiding trial group and 75.3% in the self-voiding group (p=0.01, OR 1.99, 95% CI 1.17-3.39) (Table II). Subjective outcomes were available for 428 self-voiders and 136 women in the repeat voiding trial group. The subjective success rate at 1 year was 61.0% in the repeat voiding trial group and 55.1% in the self-voiding group (p=0.23, OR 1.27, 95% CI 0.86-1.89). Success rates at one year using combined objective and subjective definitions were 59.6% for the 136 women available for analysis in the repeat voiding trial group, and 52.2% for the 429 subjects who were self-voiding (p=0.14, OR 1.35, 95% CI 0.91 - 1.99) There were 9 women who required sling release, 6 of these were in the group who required a repeat voiding trial and 3 were self-voiding at discharge. None of these were associated with mesh exposure. Analyses did not differ significantly when these women were excluded from the analysis.
Table II.
Surgical Success Rates Grouped by Voiding Trial Results
| Repeat Voiding Trial Group | Self-Voiding Group | p value | |
|---|---|---|---|
| Objective Success | 85.8% (115/134) | 75.3% (320/425) | 0.01 |
| Subjective Success | 61.0% (83/136) | 55.1% (236/428) | 0.23 |
| Objective and Subjective Success | 59.6% (81/136) | 52.2% (224/429) | 0.14 |
| Sling Release Required | 4.2% (6/143) | 0.7% (3/454) | 0.008 |
In the multivariate analysis performed, controlling for type of MUS, previous incontinence surgery, urethral mobility, urge score and pad weight, women in the repeat voiding trial group continued to demonstrate greater objective success than the self-voiding group (OR 1.82, 95% CI 1.03-3.22, p=0.04,) (Table III).
Table III.
Multivariate analysis of objective success
| Objective Success | ||
|---|---|---|
| Adjusted OR (95% CI) | p value | |
| Required repeat voiding trial | 1.82 [1.03–3.22] | 0.04 |
| Previously reported clinical predictors of success [10]: | ||
| Previous urinary incontinence surgery | 0.44 [0.25–0.78] | 0.005 |
| Pad weight (per 10g) | 0.93 [0.90–0.96] | <0.001 |
| Q-tip maximum straining <30 | 0.48 [0.29–0.81] | 0.006 |
| Preoperative Urge score (per 10 units) | 0.59 [0.33–1.06] | 0.07 |
| Transobturator MUS | 0.90 [0.58–1.39] | 0.63 |
Table IV reports the change between preoperative and postoperative UDS measures (NIF and PFS) for both groups. There were no significant differences found between the self-voiding group and the repeat voiding trial group. Both groups demonstrated comparable decreases in maximum flow rate, mean flow rate and comparable increases in detrusor pressure at maximum flow rate.
Table IV.
Change between pre- and post-operative UDS measures
| UDS measures | Difference (Post-Pre), N, Mean ± SD | p value | |
|---|---|---|---|
| NIF (Non instrumented uroflowmetry) | Self voiders (n) | Repeat voiding trial (n) | |
| Qmax (mL/s) | −4.7 ± 13.5 (334) | −5.2 ± 10.5 (95) | 0.70 |
| Qmean (mL/s) | −1.8 ± 6.4 (332) | −2.5 ± 5.1 (95) | 0.31 |
| Time to maximum flow (s) | −0.8 ± 17.9 (333) | 2.6 ± 19.7 (95) | 0.11 |
| Voided volume (mL) | 2.2 ± 152.5 (336) | 2.2 ± 151.2 (95) | >0.99 |
| Postvoid residual (mL) | 3.7 ± 46.6 (287) | 10.0 ± 52.7 (86) | 0.29 |
| PFS (Pressure flow study) | |||
| Pves at PFS baseline (cm/H2O) | −0.7 ± 11.1 (203) | −1.9 ± 12.9 (52) | 0.50 |
| Pabd at PFS baseline (cm/H2O) | −0.1 ± 11.3 (203) | −1.9 ± 11.8 (52) | 0.32 |
| Pdet at PFS baseline (cm/H2O) | −0.6 ± 5.3 (203) | −0.02 ± 5.9 (52) | 0.51 |
| Pves at maximum flow (cm/H2O) | 0.03 ± 25.0 (203) | −3.6 ± 17.8 (52) | 0.32 |
| Pabd at maximum flow (cm/H2O) | −3.0 ± 22.7 (202) | −8.7 ± 17.8 (52) | 0.10 |
| Pdet at maximum flow (cm/H2O) | 3.2 ± 12.2 (202) | 5.1 ± 10.7 (52) | 0.31 |
| Qmax (mL/s) | −2.4 ± 11.1 (344) | −3.2 ± 10.6 (95) | 0.54 |
| Time to maximum flow (s) | −4.2 ± 36.5 (334) | 3.7 ± 37.6 (95) | 0.07 |
| Voided volume (mL) | −12.5 ± 149.3 (345) | 2.8 ± 156.6 (95) | 0.38 |
Discussion
Voiding trials are widely used after SUI surgery to reduce the risk of unrecognized, clinically significant urinary retention. This analysis addressed a simple and common clinical question for surgical patients with stress urinary incontinence and their health care teams. In this randomized trial using a common definition of adequate self-voiding, we found that approximately 1 in 4 post-operative patients will require a repeat voiding trial. Although the need for a repeat post-operative voiding trial is often viewed unfavorably, the findings of our analysis suggest that we can counsel patients optimistically with regard to their objective surgical success following midurethral sling surgery.
The cause of post-operative urinary retention may be multi-factorial. While some patients may not be able to void due to iatrogenic obstruction, the causes of transient post operative retention is likely more complex and may include neuromuscular response to peri-operative medication, pain or surgical micro-trauma and swelling. While this analysis does not explain why some patients experience a need for a repeat of the post-operative voiding trial, one could postulate that transient post-operative retention might be related to increased urethral resistance. Kraus et al demonstrated that increased outlet resistance as measured urodynamically on pressure flow testing, is associated with better outcomes after Burch colposuspension and fascial slings though no such changes were seen after mid-urethral sling raising the question if the mechanism of action of MUS is different or perhaps the change in outlet resistance is not measurable with current urodynamic technology[5, 6]. Our analysis of pre- and postoperative urodynamic measures, do not suggest that those subjects requiring a repeat voiding trial show signs of greater obstruction than self-voiders. Both groups have similar decreases in maximum flow on non-instrumented uroflow and pressure flow studies and show similar increases in detrusor pressure. It is possible that there may be a subtle change in urinary outflow resistance that is related to surgical success and not necessarily associated with problematic voiding dysfunction or changes in urodynamic voiding measures.
The stress incontinence surgical literature suggests that post-operative changes to urinary outflow are common, although not clinically significant in most women. Few women in this study underwent sling release, precluding our ability to make sound conclusions about the risk for subsequent sling release following a single repeat voiding trial. However, our results do suggest that those women who require a repeat voiding trial are at increased risk for subsequent sling release. Importantly, less than 1% of self-voiding women subsequently underwent sling release.
Conclusions
It is an understandable aspect of human nature to wish to be successful, especially in health care interactions. Our common terminology of “failed” voiding trial may inadvertently have the connotation of an unfavorable or sub-optimal surgical outcome. The associated improvement in surgical success may rightfully guide us to a more “neutral” language in describing the need for a repeat voiding trial. Regardless of our terminology, the findings of this study allow us to more precisely counsel patients about their likelihood of undergoing a repeat voiding trial and its favorable relationship to surgical outcomes of midurethral sling. We should, however, caution them that this result may place them at increased risk for subsequent sling release. Our results should not be interpreted to suggest that conventional midurethral sling tensioning should be made tighter, as this trial design does not test that hypothesis. It remains unknown whether patients who needed a repeat voiding trial actually had a tighter sling than those who did not, and an analysis of urodynamic measures would suggest that this is not the case. However, we can reassure our patients that although a repeat voiding trial may remain inconvenient, there is evidence that this inconvenience may be beneficial.
Acknowledgments
This study received funding by the National Institute of Diabetes and Digestive and Kidney Disease, as well as the National Institutes of Health.
References
- 1.Kleeman S, et al. Predicting postoperative voiding efficiency after operation for incontinence and prolapse. Am J Obstet Gynecol. 2002;187(1):49–52. doi: 10.1067/mob.2002.124841. [DOI] [PubMed] [Google Scholar]
- 2.Kobak WH, Walters MD, Piedmonte MR. Determinants of voiding after three types of incontinence surgery: a multivariable analysis. Obstet Gynecol. 2001;97(1):86–91. doi: 10.1016/s0029-7844(00)01103-0. [DOI] [PubMed] [Google Scholar]
- 3.Richter HE, et al. Retropubic versus transobturator midurethral slings for stress incontinence. N Engl J Med. 2010;362(22):2066–2076. doi: 10.1056/NEJMoa0912658. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Norton P, et al. Risk Factors for Incomplete Bladder Emptying After Midurethral Sling. International Continence Society Meeting Abstract #12. 2011 [Google Scholar]
- 5.Kraus SR, et al. Urodynamic changes associated with successful stress urinary incontinence surgery: is a little tension a good thing? Urology. 2011;78(6):1257–1262. doi: 10.1016/j.urology.2011.07.1413. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Kraus S, et al. Urodynamic Changes 12 Months after Retropubic and Transobturator Midurethral Slings. International Continence Society Meeting Abstract #13. 2011 [Google Scholar]
- 7.UITN. The Trial of Mid-Urethral Slings (TOMUS): design and methodology. J Applied Res. 2008;8:1–13. [PMC free article] [PubMed] [Google Scholar]
- 8.Schafer W, et al. Good urodynamic practices: uroflowmetry, filling cystometry, and pressure-flow studies. Neurourol Urodyn. 2002;21(3):261–274. doi: 10.1002/nau.10066. [DOI] [PubMed] [Google Scholar]
- 9.Nager CW, et al. Urodynamic measures do not predict stress continence outcomes after surgery for stress urinary incontinence in selected women. J Urol. 2008;179(4):1470–1474. doi: 10.1016/j.juro.2007.11.077. [DOI] [PubMed] [Google Scholar]
- 10.Richter HE, et al. Demographic and clinical predictors of treatment failure one year after midurethral sling surgery. Obstet Gynecol. 2011;117(4):913–921. doi: 10.1097/AOG.0b013e31820f3892. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Shumaker SA, Wyman JF, Uebersax JS, et al. Health-related quality of life measures for women with urinary incontinence: the Incontinence Impact Questionnaire and the Urogenital Distress Inventory. Qual Life Res. 1994;3:291–306. doi: 10.1007/BF00451721. [DOI] [PubMed] [Google Scholar]
- 12.Herzog AR, Diokno AC, Brown MB, et al. Two-year incidence, remission, and change patterns of urinary incontinence in noninstitutionalized older adults. J Gerontol. 1990;45:M67–M74. doi: 10.1093/geronj/45.2.m67. [DOI] [PubMed] [Google Scholar]