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2002 Selected Articles

Surgery for Genuine Stress Urinary Incontinence, Part 2: Suburethral Sling Procedures and Urethral Bulking Agents

Rebecca G. Rogers, MD; Dorothy N. Kammerer-Doak, MD

In part 1, the authors discussed two common procedures for treating genuine stress urinary incontinence (GSUI): anterior repair and Burch retropubic urethropexy (RPU). Evidence from randomized trials supports the Burch RPU as a better treatment for GSUI, with higher objective and subjective cure rates. This concluding article addresses two other procedures for GSUI, sling urethropexy and urethral bulking agents. Until recently, gynecologists rarely used suburethral slings for the primary treatment of GSUI, reserving these procedures for women with recurrent or complicated GSUI. However, for some practitioners, slings have evolved into a first-line treatment for GSUI.

SLING URETHROPEXY

Background

The first sling procedures utilized muscle flaps, with the belief that these would acquire a sphincter-like function by maintaining contractility. Complications were frequent, including fistula, urethral slough, outlet obstruction, retropubic sepsis, and recurrent cystitis. Musculature slings were ultimately abandoned due to the difficulty in preserving the muscle’s blood supply and mechanical problems associated with incorporating bulky tissue beneath the urethra.^1,2

Aldridge² developed the precursor to the modern sling procedure in 1942 using two transverse strips of rectus fascia that were detached at their lateral margins and then sutured beneath the urethra via a separate vaginal incision. He described this sling as compressing the urethra during times of increased intra-abdominal pressure, a concept that still explains the mechanics of continence following sling procedures today.^1,2 The more common use of slings in gynecology began with the observation by Sand et al³ in 1987 of a high failure rate in women with low pressure urethra, intrinsic sphincter deficiency, (ISD) who underwent traditional retropubic procedures. Higher success rates were achieved in these women with sling procedures.³ Because of these observations, many gynecologists reserved sling surgeries for GSUI patients with ISD or for women who had failed primary incontinence procedures such as anterior repair or Burch RPU.

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Theory

Both the Burch RPU and suburethral sling procedures act to stabilize the suburethral fascia and urethra, resulting in more effective transmission of intra-abdominal pressure to the urethra. Historically, these surgeries were described as elevating the urethrovesical junction, restoring it to a retropubic, intra-abdominal position. These procedures provide a suburethral “hammock” that compresses the urethrovesical junction when intra-abdominal pressure rises, resulting in an element of obstruction. Since sling procedures utilize a piece of material that passes completely under the urethra, there is the possibility of greater obstruction as compared to the Burch RPU in which only sutures are placed on either side of the urethra. Such obstruction was thought to produce higher success rates with the sling as compared to the Burch RPU for the treatment of women with GSUI and ISD.⁴

Although the definition of ISD is not standardized, low-pressure urethras correspond to previous descriptions of “lead pipe” or “type 3” urethras. On urodynamic evaluation, ISD is suggested by a maximal urethral closure pressure of less than 20 cm of water or an abdominal leak-point pressure of less than 60 cm of water. On cystourethrography, the bladder neck appears open. The incidence of ISD ranges from 11% in a population of women with primary incontinence to 50% in women from a referral population.^5,6

An alternative theory of incontinence proposed by Ulmsten⁷ suggests that continence in the female is maintained at the midportion, the area representing the highest urethral pressures urodynamically, and not the bladder neck. Lack of support at the midurethra and suburethral vaginal wall, plus impairment of pubococcygeal muscle function predisposes women to GSUI. To address this, newer procedures pass the sling from the vagina to the abdomen at the midurethra rather than the urethrovesical junction.⁸

However, many women with hypermobility of the bladder neck and proximal urethra do not have GSUI, implying that GSUI must involve some deficiency in the bladder sphincteric mechanism. Thus, the proponents of primary sling procedures for all women with GSUI, and not just those with ISD, contend that they treat both GSUI secondary to hypermobility and ISD.⁹ The argument against the suburethral sling as a primary treatment for GSUI focuses on reports of increased morbidity. Other concerns include the need for vaginal wall dissection, with the consequent risks of scarring, denervation, and fibrotic changes that could further damage the urethral sphincter mechanism. These are problems that may be circumvented by newer techniques.

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Technique

Most sling procedures involve placing a strip of supportive material beneath the urethra (Figure 1) using a combined abdominal and vaginal approach. Either a long strip of sling material is placed in the retropubic space and anchored to the rectus fascia, or a “patch” of sling material is extended under the urethra with suture bridges. A single randomized trial found no difference in patient satisfaction at 1 year between women who received a “string” or a full-length sling. (74% vs 70%, respectively, p < 0.05), although no objective data were reported.¹⁰ Vaginal fixation of the sling is traditionally at the urethrovesical junction.

 

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Figure 1. In this type of sling a long strip of fascia lata, harvested from the inner thigh, is passed up through the retropubic space with the aid of a long clamp. One end is sutured into position in the rectus fascia and the tension is adjusted before sewing the other end in place. Ridley JR (Ed). Gynecologic Surgery: Errors, Safeguards, Salvage, 2nd ed. Baltimore: Williams and Wilkins, 1981, with permission.

The search for the perfect sling material is ongoing. Many different autologous, allogenic, and synthetic materials have been tried. With the aim of reducing morbidity and operative time, various synthetic materials have been utilized including Marlex (CR Bard), Mersilene (Ethicon), and Gore-Tex (WL Gore). More recently, Ulmsten¹¹ in 1996 utilized polypropylene mesh with a unique placement technique that he described as a tension-free vaginal tape (TVT) procedure. However, with the exception of reported low erosion rates for TVT, synthetic grafts are associated with relatively high rates (3% to 34%) of infection, erosion, fistula formation, and rejection.¹²

Because of such complications, many surgeons choose to use autologous fascia harvested from the patient. This requires a separate incision to obtain the graft, with consequent increases in operative and recovery times. Another alternative is the use of allogenic fascia. The use of cadaveric fascia, which was first described in 1996, was popular until reports of autolysis and unexpectedly high early failure rates began to accrue.^13,14

There are few randomized studies to suggest which material offers the highest cure rate for GSUI with the fewest complications. In a small, randomized trial comparing rectus fascia with Gore-Tex slings, 11 of 32 (34%) patients with rectus fascia slings versus 2 of 16 (12.5%) patients with Gore-Tex slings were not cured at 30 months (relative risk [RR] 0.36, 95% confidence interval [CI] 0.09 to 1.45) a difference that did not reach statistical significance. Fewer women with autologous slings had complications (0/32 vs 5/16; RR 21.35, 95% CI 1.25 to 363.78).¹⁵

The focus on suburethral slings has intensified since the introduction of the TVT technique, which incorporates many principles already employed in sling placement (Figure 2). Minimal vaginal-wall dissection is important to reduce the risk of scarring and denervation, and the sling is adjusted so that it is not under tension to minimize postoperative voiding dysfunction. Placement is at the midurethral as opposed to the urethrovesical junction, conforming to the integral theory of continence. The polypropylene mesh is associated with decreased tissue inflammatory reactions when compared with other synthetic sling materials,¹⁶ and it is inserted using a plastic sheath that is then removed. The tape can be placed under local anesthesia in an outpatient setting and usually does not require the use of a catheter.⁸ The TVT procedure has been shown to be effective in the treatment of primary and recurrent GSUI, as well as incontinence in patients with ISD.^17,18 The complication rate is approximately 1/11; the most common problem is bladder perforation. The majority of complications are minor and do not require additional surgical intervention.¹⁰ Several other suburethral sling kits have been introduced recently, however, little published data exists to evaluate their efficacy or complication rates.

 

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Figure 2. Gynecare slide package.

Several large registries are compiling complications associated with TVT placement. An Austrian registry of 2,795 patients reported a bladder perforation rate of 2.7%, with higher rates in women with prior incontinence surgery (4.4% vs 2.0%, p = 0.01). Most patients voided on the day after their surgery. Reoperation for reasons associated with tape placement (hematoma; bowel injury; loosening, removal, or cutting the tape; or placement of suprapubic catheter) was 2.4%.¹⁹

At the authors’ institutions, patients are offered autologous abdominal wall facial or TVT sling. The technique for autologous sling involves the harvest of an 8- to 10-cm strip of rectus fascia through a small suprapubic incision. The anterior vaginal wall is dissected to expose the urethrovesical junction, where the sling is secured with fine, delayed, absorbable sutures. The ends of the sling are extended using 0–0 prolene sutures, which are brought up through the retropubic space with Stamey needles to the suprapubic incision. The prolene sutures are then anchored to the rectus fascia. Minimal tension is placed on the sling. The authors also offer patients TVT slings placed under local anesthesia as described by Ulmsten.¹¹ The mesh tape is placed at the midurethra with minimal tension, and adjusted in the operating room as the patient coughs or performs a Valsalva maneuver.

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SLING URETHROPEXY VERSUS BURCH RPU

Outcomes for the suburethral sling and Burch RPU are both excellent. Overall short-term cure rates are similar (RR 0.93; 95%, CI 0.68 to 1.27).¹⁰ However, suburethral slings have been associated with an increased incidence of urinary retention, detrusor instability, injury to the lower urinary tract (including cystotomy, erosion into the urethra or vagina, and fistula formation), as well as the need for additional surgery to correct iatrogenic complications such as erosion/rejection of the sling material. Two large series address some of these complications. Of 110 women undergoing Mersilene mesh suburethral sling procedures, 3 (2.7%) developed long-term urinary retention, 2 (0.9%) developed graft erosions, and 19% developed significant urgency symptoms.²⁰ In another series, 98 women receiving Gore-Tex suburethral slings needed prolonged bladder drainage with suprapubic catheters for a mean of 10.7 weeks, with eight women (8%) requiring intermittent self-catheterization and 4% reporting voiding difficulties necessitating the Crede maneuver, double void maneuvers, or upright voiding.²¹ In an earlier paper, the same authors reported high rates of postoperative wound complications in 40% of 108 patients following placement of Gore-Tex suburethral slings, resulting in 22% of grafts eventually removed secondary to erosion, persistent vaginal granulation tissue, abdominal wound abscess, or sinus tract formation.²² In this series, detrusor instability was common: of 45 patients with a stable bladder on urodynamic testing preoperatively, 33% developed postoperative detrusor instability, a rate much higher than the 8% noted with fascial suburethral slings.²³

Reports of increased complications with suburethral sling procedures are subject to debate. A retrospective review of complications following sling procedures may be inappropriate, as slings were historically reserved for women with complicated or recurrent GSUI. In addition, modifications over recent years have reduced complications. Using the “patch” or in-situ sling techniques with minimal tension on the sling can yield cure rates of 85%, with rates of detrusor instability ranging from 12% to 30%. With these techniques, prolonged urinary retention is only 3% more likely than with Burch RPU.^24,25

Twelve retrospective studies have compared the results of suburethral sling with those of Burch RPU, with only one reporting a difference in outcomes.²⁶ In this single trial, the cure rate for Burch RPU (136 procedures) was reported as 97% compared with 82.5% for the suburethral sling (164 procedures), and the difference was significant (P < 0.001).

Randomized data comparing Burch RPU to suburethral sling are scarce, with only four reported trials. The numbers in three of the trials are small, and most of the follow-up is short-term. None of the studies reported a difference in cure (however defined) between RPU and suburethral sling, regardless of whether the operations were primary or secondary (repeat) procedures. However, all had substantially less than 50% power to detect a clinically significant difference. The first three trials compared results for the treatment of secondary incontinence (Table).^27-29 Henriksson’s study²⁷ reported limited numbers with short-term follow-up, and alternated surgical procedures rather than randomizing patients. Enzelsberger²⁸ reported objective data for 72 of 77 women randomized to either Burch RPU or lyodura suburethral sling after 32 to 48 months of follow-up. There was no difference between groups in objective cure (86% Burch RPU vs 92% suburethral sling). However, in comparing various urodynamic parameters preoperatively and postoperatively, significant changes were noted, including increased urge symptoms, detrusor instability, decreased maximum cystometric capacity, increased urinary retention (postvoid residual volume exceeding 100 mL), and increased voiding difficulties in the sling group (p < 0.05). Use of suprapubic catheters was prolonged in the suburethral sling group (6.4 vs 12.4 days, p < 0.05). Rectoceles (grade II or greater) were noted in 13% of the women in the Burch group compared with 3% in the suburethral sling group (p < 0.05). All failures were found to have insufficient elevation of the bladder neck (less than 10 mm) by transperineal ultrasonography.

 

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Table. Comparison of Burch RPU With Sling Urethropexy

Ward et al³⁰ recently published the latest randomized trial, in which 316 patients were assigned to either TVT or Burch RPU. Cure was defined as a combination of subjective and objective measures, and may account for the lower rates seen with both procedures (57% vs 66% subjective and objective cure with Burch RPU and TVT, respectively, p = 0.099). Intraoperative complications, particularly bladder injury, were more common with the TVT group, while postoperative complications were more common in the Burch RPU group. Operative time, hospital stay, and return to normal activity were all shorter with the TVT procedure.³⁰ The findings in this randomized trial are supported by several prospective trials with up to 5 years of follow-up.^4,8

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URETHRAL BULKING PROCEDURES

Another approach to the surgical treatment of GSUI is to increase the resistance at the bladder neck through bulking agents. Various materials have been used for periurethral injection, including sodium morrhuate, wax, sclerosing agents, autologous fat, and Teflon.³¹ In 1993, the US Food and Drug Administration approved glutaraldehyde cross-linked collagen to treat urinary incontinence. The procedure is performed under local anesthesia by advancing a needle to the urethrovesical junction and injecting collagen until the urethra coapts (Figures 3, 4, 5). One month prior to injection, patients require a skin test for collagen allergy. Success rates, defined as “improved” and/or “dry,” range from 30% to 70% at 1 year and decline thereafter, with recurrence of incontinence generally by 2 years.³² It was theorized that permanent continence would occur when fibroblasts migrated to the site to replace the injected collagen with endogenous collagen. However, injected collagen is generally reabsorbed, leading to the failure of the procedure over time. Many patients require repeat procedures, with more than three injections unlikely to improve continence rates.

 

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Figure 3. The endoscope is in position in the urethra, and is positioned in the bladder neck. The periurethral injection needle is advanced alongside the urethroscope. After the site for injection has been determined by injection of indigo carmine-stained local anesthetic, the collagen is placed. Cundiff GW, Bent AE. Endoscopic Diagnosis of the Female Lower Urinary Tract. 1999;79, with permission.

 

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Figure 4. Open bladder neck. The urethrovesical junction is visualized just before collagen injection, using a 0° or 12°. Cundiff GW, Bent AE. Endoscopic Diagnosis of the Female Lower Urinary Tract. 1999;79, with permission.

 

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Figure 5. Complete periurethral injection of collagen. Injected collagen is completed by periurethral technique, and the bladder neck is now closed. Cundiff GW, Bent AE. Endoscopic Diagnosis of the Female Lower Urinary Tract. 1999;80, with permission.

Because of the poor long-term success rates with collagen, newer bulking agents have been developed, including pyrolytic carbon-coated zirconium beads (Duraspheres). The beads were designed to be permanent, nonreactive and nonmigratory. In a single randomized trial comparing collagen with Duraspheres, no difference was noted in the number of injections required or the success rates at 1 year.³³ However, follow-up studies have not been reported comparing longer-term success rates.³² The beads are injected in the same manner, and there is no need for a skin test prior to the injection. Special needles are required, and some practitioners have reported difficulty with injecting the material due to the difference in viscosity of the beads and the suspension gel.

Urethral bulking agents were originally thought to have better success rates in women with immobile urethras. However, several studies report comparable success rates in women with urethral mobility.^34,35 For patients with immobile urethras, however, few alternatives offer better success rates. In one small series, suburethral sling procedures in patients with immobile urethras had failure rates of up to 80%.³⁶ For patients with an immobile low-pressure urethra, bulking agents provide a minimally invasive procedure with equivalent success rates to more invasive and morbid procedures. Reported complications with urethral bulking agents are few, including transient urinary retention, urinary tract infection, and de novo urge incontinence.³² In the single randomized trial comparing collagen with Duraspheres, the women in the Durasphere group reported an increased risk of short-term urgency and urinary retention.³³

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CONCLUSION

These two articles have reviewed some of the common procedures for the treatment of GSUI (Figure 6). Randomized trials support the choice of Burch RPU over anterior repair for the treatment of GSUI, and suggest that cure rates for GSUI with suburethral slings and Burch RPU are similar. The literature shows that slings result in increased complications when compared with Burch RPU. The TVT sling permits outpatient surgical treatment of GSUI, with the benefit of decreased operative time and hospital stay plus fewer long-term complications compared with Burch RPU. The delivery system for placing polypropylene mesh slings has been well studied in prospective cohort and randomized trials, and offers excellent results at 5 years of follow-up. Urethral bulking agents offer a minimally invasive procedure for the treatment of GSUI, with few complications but poor long-term success rates. The ultimate choice of surgical procedure should be based on a comprehensive discussion between surgeon and patient, and be individualized to the patient’s needs.

 

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Figure 6. Decision Paradigm for Surgery for GSUI

Rebecca G. Rogers, MD, is director, Division of Urogynecology, and assistant professor of obstetrics and gynecology at the University of New Mexico, Albuquerque. Dorothy N. Kammerer-Doak, MD, is associate clinical professor, Department of Obstetrics and Gynecology, University of New Mexico, and urogynecologist, Lovelace Health Systems, Albuquerque, NM.

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REFERENCES

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29. Sand PK, Winkler H, Blackhurst DW, Culligan PJ. A prospective randomized study comparing modified Burch retropubic urethropexy and suburethral sling for treatment of genuine stress incontinence with low-pressure urethra. Am J Obstet Gynecol. 2000;182(1 Pt 1):30-34.
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31. Herschorn S, Radomski SB. Collagen injections for genuine stress urinary incontinence: patient selection and durability. Int Urogynecol J. 1997;8:18-24.
32. Lightner DJ. Review of available urethral bulking agents. Curr Opin Urol. 2002;12(4):333-338.
33. Lightner D, Calvosa C, Andersen R, et al. A new injectable bulking agent for treatment of stress urinary incontinence: results of a multicenter, randomized, controlled, double-blind study of Durasphere. Urology. 2001;58(1):12-15.
34. Steele AC, Kohli N, Karram MM. Periurethral collagen injection for stress incontinence with and without urethral hypermobility. Obstet Gynecol. 2000;95(3):327-331.
35. Bent AE, Foote J, Siegel S, et al. Collagen implant for treating stress urinary incontinence in women with urethral hypermobility. J Urol. 2001;166:1354-1357.
36. Summitt RL Jr, Bent AE, Ostergard DR, Harris TA. Stress incontinence and low urethral closure pressure. Correlation of preoperative urethral hypermobility with successful suburethral sling procedures. J Reprod Med. 1990;35(9):877-880.

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