Urethral Slings

ALEX GOMELSKY

A form of “sling surgery” to treat female stress urinary incontinence (SUI) has existed for over a century. Despite the sequential implementation of various autologous tissues, allografts, xenografts, and synthetic materials, the sling procedure has traditionally been associated with significant complications and has been commonly reserved for the treatment of refractory SUI. However, owing to an improved understanding of SUI pathophysiology through the work of groups led by DeLancey (1), McGuire and Lytton (2), Blaivas and Jacobs (3), and Petros and Ulmsten (4), the sling has emerged over the last two decades as a reproducible, efficacious, and safe surgical option. Furthermore, novel materials, methods of suspension, and routes of placement have only served to decrease operative time and shorten convalescence, contributing to the sling becoming a contemporary gold standard for the surgical treatment of women with SUI. The focus of this chapter will be to describe the surgical technique behind the autologous rectus fascia bladder neck sling (BNS) and the retropubic and transobturator approach to the midurethral sling (MUS). Although there are several commercial options for approaches to the MUS, the operative procedure and anatomic landmarks are relatively standardized. Thus, I will describe only one example product for each type of approach for the retropubic and transobturator MUS. There will be no additional discussion of other materials placed at the bladder neck, and the single-incision minisling is, likewise, not discussed in this chapter. A brief review of surgical outcomes, comparative studies, and complications follows.

PATHOPHYSIOLOGY OF STRESS URINARY INCONTINENCE

It is universally accepted that continence during increases in intra-abdominal pressure depends on a complex interaction between urethral support, intrinsic urethral properties, the sphincter complex, and adjunct pelvic floor musculature. Two current theories build the case regarding the location of the anatomic weakness that contributes to SUI. In his “hammock hypothesis,” DeLancey (1) postulated that the urethra is supported by a hammock-like layer consisting of the vaginal wall and endopelvic fascia that is stabilized by lateral attachments to the levator ani and the arcus tendineus fascia pelvis. Along with the urethropelvic ligaments, these structures envelop the proximal urethra and aid in closure of the urethral lumen during increases in abdominal pressure. Slings placed at the bladder neck and proximal urethra aim to address this weakness. Conversely, in the “integral theory,” Petros and Ulmsten (4) proposed that the midurethra is the linchpin in the continence mechanism. The authors postulated that contraction of the pubococcygeus muscle during increases in abdominal pressure pulls the anterior vaginal wall forward and closes off the urethral lumen, a response that is contingent on an intact attachment between the pubourethral ligaments and anterior vaginal wall. Laxity in this midurethral fulcrum may subsequently lead to funneling of the urethra and urinary incontinence. The midurethra is the location for placement of the “tension-free” synthetic slings.

DIAGNOSIS

The American Urological Association (AUA) guidelines on SUI state that the minimum workup for an index patient presenting with SUI symptoms should include a history, pelvic examination, urinalysis and culture (if indicated), objective demonstration of incontinence (e.g., during cough stress testing), and assessment of postvoid residual urine (standard) (5). The index patient is an otherwise healthy female who has elected surgical therapy for the correction of SUI, may be untreated or previously surgically treated, and may have urethral hypermobility and/or intrinsic sphincter deficiency (ISD). The panel made a recommendation to add additional diagnostic studies to assess the integrity and function of the lower urinary tract: pad testing
and/or voiding diary, urodynamics, cystoscopy, and imaging. Likewise, the panel made a recommendation to consider further testing for the following indications: inability to make a definitive diagnosis based on symptoms and/or the initial evaluation, concomitant overactive bladder symptoms, prior lower urinary tract surgery (including failed anti-incontinence procedures), known or suspected neurogenic bladder, negative cough stress test, abnormal urinalysis such as unexplained hematuria or pyuria, excessive residual urine volume, grade III or higher pelvic organ prolapse, and any evidence for dysfunctional voiding. Although there is some controversy regarding the role of urodynamics in cases of primary SUI, these diagnostic studies may be especially helpful in cases of mixed urinary incontinence, concomitant pelvic organ prolapse, incomplete emptying or neurogenic micturition dysfunction, and prior surgical failure (5).

ALTERNATIVE THERAPIES

Several nonsling options exist for the treatment of SUI. In women with mild or nonbothersome SUI, active treatment may be postponed until the incontinence impacts the patient’s quality of life. If active treatment is elected, pelvic floor muscle training with the potential addition of biofeedback may provide the woman significant improvement. Furthermore, urethral bulking therapy is another option that may provide benefit with minimal anesthetic requirement and procedural morbidity. Although the long-term benefit of this mode of therapy varies significantly in the literature, this remains a viable option in a select population. Finally, several additional, albeit infrequently performed, procedures are available for the surgical correction of SUI. Of these, transvaginal needle suspensions and suburethral plications have been associated with poor long-term outcomes and were not included in the most recent AUA SUI guidelines (5). Although the AUA Guidelines Panel found little new data regarding the efficacy of retropubic bladder neck suspensions (e.g., Burch or Marshall-Marchetti-Krantz), they concluded that there continues to be evidence for the efficacy of these procedures in selected patients (5).

INDICATIONS FOR SLING SURGERY

The introduction of the MUS can be viewed as a watershed event in the century of sling surgery. The novel procedure championed by Petros and Ulmsten was not only unique in its anatomic placement but also in its minimally invasive nature and reproducible outcomes. The transobturator MUS has gained further popularity because this approach avoids entry into the space of Retzius, thus potentially minimizing the serious viscus or neurovascular injuries that may occur from errant trocar placement during the retropubic approach (6). Owing to these advantages, the MUS has largely supplanted the rectus fascia BNS for most patients. One scenario where a BNS may continue to serve as the primary surgical option is in women who are undergoing a concomitant debridement of a MUS that has eroded into the vagina or urinary tract. Initially, it was also felt that ISD may be another relative indication for a BNS, as cure rates less than 20% were cited in these women who had a MUS (7). However, several authors have since noted that the retropubic MUS is associated with durable cure rates over the long term (8,9), and these exceed the cure rates seen with the transobturator approach in the ISD population (10,11). Ultimately, sling choice will be determined by the surgeon’s training and experience as well as a detailed informed consent discussion with the patient.

A few details remain once the decision to pursue operative therapy has been made. Although not all elements of vaginal prolapse require repair, consideration must be given to addressing prolapse at or distal to the hymenal ring, or symptomatic prolapse of a lesser degree, at the time of sling surgery. Doing so may minimize the possibility of SUI recurrence, urinary retention, or worsening prolapse.

A discussion of the risks, benefits, and options to sling surgery is key in obtaining informed consent. Risks may be intraoperative (bleeding, potentially requiring transfusion; injury to the bladder or urethra; hematoma formation), early postoperative (<30 days: urinary retention and other voiding symptoms; urinary tract infection; de novo, persistent, and/or worsened storage symptoms), and late postoperative (>30 days: urinary retention; need for urethrolysis or sling revision; dyspareunia; recurrent or de novo prolapse and SUI; de novo, persistent, and worsened storage symptoms). Harvest site complications, including seroma formation and infection, are relatively unique to rectus BNS. The risk of complications such as sling erosion and extrusion should also be mentioned. Although these sequelae are most commonly associated with synthetic mesh placement, any sling may erode into the urethra if placed under excessive tension.

SURGICAL TECHNIQUE

Preoperative Considerations

The following considerations apply for both BNS and MUS. A preoperative bowel regimen is typically not ordered for a sling-only procedure but can be considered for surgeries including a concomitant hysterectomy, vaginal vault suspension, or posterior compartment surgery. Prophylactic intravenous antibiotics are given within an hour of surgical “cut” time (first- or second-generation cephalosporin, gentamicin and clindamycin, or a fluoroquinolone) (12). Antithromboembolic hose and/or sequential compression devices are applied prior to induction of anesthesia. Regional or general anesthesia may be used for all slings, whereas local anesthetic protocols may be used for MUS. The ultimate choice of anesthesia is at the discretion of the surgeon, anesthesiologist, and patient. The pubic hair is clipped in the operating room. The patient is positioned in slightly exaggerated dorsal lithotomy position in Allen stirrups. Skin preparation is performed from below the umbilicus to the midthigh, and the vaginal canal is also prepped. After draping, an indwelling urethral catheter is placed to continuous drainage. A weighted vaginal speculum and Scott/Lone Star retractor may be of assistance in obtaining exposure. Liberal irrigation of the vaginal incision is performed throughout the case often with neomycin sulfate-polymyxin B sulfate solution or an alternative solution. Many surgeons will submerge the chosen sling material in antibiotic irrigation until ready to use. If a concomitant transvaginal procedure is planned to repair an anterior compartment prolapse, I prefer to make a separate midurethral incision for a MUS;
however, I would use a single vaginal mucosal incision to address both the incontinence and prolapse if a rectus fascia BNS is planned. The AUA Guidelines Panel recommended that tensioning of any sling should not be performed until prolapse surgery is completed (5). Thus, it is my routine to perform all of the prolapse surgery first and conclude with the sling procedure.

Rectus Fascia Bladder Neck Sling

Fascial Harvest and Abdominal Incision

A low transverse incision two fingerbreadths above the superior edge of the pubic symphysis provides excellent exposure and cosmesis. The rectus fascia is exposed after incising the skin, subcutaneous fat, and Scarpa fascia. It is important not to excessively undermine the areolar tissue overlying the rectus fascia because this may increase the possibility of postoperative seroma. A strip of fascia measuring approximately 1.5 cm × 7 cm is excised and 2-0 polypropylene sutures are attached to each end (Fig. 43.1). The sling is soaked in antibiotic solution until the vaginal incision is prepared. The fascial rent is closed with continuous or interrupted no. 1 delayed absorbable suture. The skin and Scarpa layer are left open for the upcoming passage of sling sutures. Although there is no consensus regarding optimal sling length, it is widely accepted that the sling should be long enough to reach the space of Retzius and provide both suburethral and paraurethral support. Alternatively, autologous fascia lata harvested from the thigh is an alternative to rectus fascia. The use of this tissue may require patient repositioning and special instrumentation.

Vaginal Dissection

An inverted U incision provides excellent access to the bladder neck, with the apex of the U at the midurethra and the widely spaced legs of the U extending just proximal to the bladder neck. Alternatively, a vertical midline incision may be used. The anterior vaginal wall may be infiltrated with normal saline or a hemostatic agent. The vaginal mucosa is dissected sharply off the underlying surface of the pubocervical and periurethral fascia, with lateral dissection proceeding up to the inferior edge of the pubic symphysis. The endopelvic fascia on each side of the urethra is perforated with Metzenbaum scissors and the space of Retzius is entered. The scissors should be aimed at the ipsilateral shoulder and remain just inferior to the pubic symphysis to minimize the possibility of bladder or vascular injury. Once the endopelvic fascia is perforated, paraurethral adhesions in the retropubic space may be released with an index finger.

FIGURE 43.1 The rectus fascia graft is harvested and attached to 2-0 polypropylene sutures.

Suture Passer Advancement

Any concomitant surgery to address anterior or apical compartment prolapse should be completed prior to suture passer advancement. Double-pronged needles (Cobb-Ragde) are used to pierce the rectus fascia approximately 2 cm lateral to the midline and remain immediately posterior to the pubic symphysis. A finger in the retropubic space from below may be used to guide the needle out of the vaginal incision on either side of the urethra (Fig. 43.2). Alternatively, a tonsil-tipped clamp, single-pronged (Stamey) or double-pronged (Raz) needle passer may be used. Ensuring that the bladder is completely empty prior to needle passage may minimize the possibility of bladder puncture.

Cystoscopy

An ampule of indigo carmine dye is given intravenously. Ureteral integrity is confirmed on cystoscopy when blue-tinged urine effluxes from each ureteral orifice. A 70-degree lens may be helpful to visualize the dome and superolateral aspects of the bladder where penetration with passers is most likely to occur. It is vital to evacuate the air bubble and inspect that area carefully, as it may occasionally obscure the metal passers. It is also imperative to adequately visualize the entire path of the passer from the dome to the bladder neck and proximal urethra, as bladder integrity may be compromised anywhere along this path. If the bladder has been penetrated, the offending suture passer should be removed under direct vision, the bladder drained, and the needle should be passed again. Cystoscopy should be performed after each additional pass. Prolonged continuous catheter drainage should be considered to allow for additional bladder healing in the event of a bladder or urethral injury. The AUA Guidelines Panel concluded that intraoperative cystourethroscopy should be performed in all patients undergoing sling surgery (standard) (5).

FIGURE 43.2 A double-headed needle is passed bilaterally through the rectus fascia and into the vaginal incision on either side of the urethra.

FIGURE 43.3 The sling is positioned flat at the bladder neck and anchored to the periurethral fascia to keep it from slipping during the tensioning process. The vaginal incision is then closed.

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