Pubovaginal Fascial Slings
March 26, 2009 Leave a comment
The first urethral sling procedure was described by Von Giordano in 1907. However, even after numerous technical improvements and application of many different materials, the pubovaginal sling (PVS) was rarely used until repopularized by McGuire and Lytton in 1978. The pubovaginal sling has traditionally been used only when other incontinence procedures such as a bladder neck suspension or retropubic urethropexy have failed. In this regard, patients with type 3 stress urinary incontinence, also called intrinsic sphincter deficiency (ISD), have often been diagnosed by default. More recently, the preoperative diagnosis of ISD has been facilitated by use of the Valsalva or abdominal leak point pressure (ALPP) during incontinence evaluations. Accordingly, the diagnosis of ISD can be made before surgery and a PVS performed as the primary incontinence procedure.
Stress urinary incontinence in females is classified by the presence and degree of urethral mobility and functional status of the urethra. In types I and II stress urinary incontinence, the urethral sphincter functions normally; however, abdominal pressure can drive the sphincter to a position where it doesn’t function normally. Stress incontinence due to urethral hypermobility can be successfully treated by a procedure that immobilizes it, such as a retropubic urethropexy or needle suspension procedure. Type III stress urinary tract incontinence, or ISD, is usually characterized by a minimally mobile urethra and incompetence of the urethral sphincter during increases in abdominal pressure. A few patients have incontinence due to coexisting ISD and urethral hypermobility. All patients with ISD are effectively treated with a PVS.
The preoperative evaluation is directed to identifying ISD. The history can be helpful because patients with ISD usually have severe leakage with minimal activity or have a history of irradiation to the pelvis, a prior incontinence procedure, or are elderly (especially new onset in patients over 70 years old). The incidence of ISD increases after each failed incontinence procedure: 9% if no previous surgery, 25% after one failed procedure, and 75% after two failed procedures.
The physical exam is directed to demonstrating leakage, urethral hypermobility, and pelvic prolapse. Urinary leakage without significant hypermobility constitutes presumptive evidence of ISD. A careful evaluation for associated cystocele, rectocele, enterocele, and uterine prolapse is important for ALPP interpretation and in planning the appropriate operative procedures. Failure to repair associated pelvic prolapse conditions will put undue stress on any incontinence procedure, including a pubovaginal sling, which increases the failure rate.
After the postvoid residual is determined, a cystometrogram is performed to exclude poor detrusor compliance and overt detrusor instability. To diagnose ISD, an ALPP is indispensable. The bladder is filled to a standard volume of 200 ml (children to one-half functional bladder capacity) and a slow Valsalva maneuver is performed with the patient in the upright position until leakage is noted. Performing this several times and determining an average improves accuracy. If a well-performed Valsalva maneuver fails to induce leakage, vigorous coughing may be required. If the ALPP is below 60 cm H2O, then ISD is present. If the ALPP is greater than 90 cm H2O and minimal pelvic prolapse exists, pure urethral hypermobility is usually present. Patients with a significant pelvic prolapse condition may have a falsely elevated ALPP and reduction with a vaginal pack is helpful. ALPP values between 60 to 90 cm H2O form a gray area in which hypermobility and ISD usually coexist.
INDICATIONS FOR SURGERY
The most common indications for a PVS are urodynamically documented ISD with or without urethral hypermobility and a prior failed incontinence procedure. Additionally, because of the long-term success and durability of a pubovaginal sling, certain patients with stress urinary incontinence due to urethral hypermobility may be better served with a sling procedure. These include females who engage in vigorous athletic activities, are significantly obese, or who cough frequently due to pulmonary disease.
In selected female patients with ISD and minimal urethral hypermobility, collagen can be injected at the bladder neck with a success rate of 63% using a mean of 9.1 ml and 1.5 treatments. The vaginal wall sling introduced by Raz uses the in situ vaginal wall as the sling with a reported 93% short-term cure rate in patients with ISD.
Patients with atrophic vaginitis should be treated with topical estrogens for 2 weeks before the procedure. It is helpful to teach the patient clean intermittent catheterization before the procedure since incomplete emptying is common for a few days postoperatively. One dose of intravenous antibiotics should be given preoperatively. General or regional anesthesia may be used without particular advantage to either technique.
The procedure is performed in the low lithotomy position using Allen stirrups with feet squarely in the stirrups to avoid pressure on the calf areas. The legs should only be moderately flexed at the hips to allow simultaneous exposure to the vagina and the lower abdomen. A 16-Fr Foley catheter is placed and the balloon inflated with 5 mls to allow palpation of the bladder neck and urethra. A weighted vaginal speculum is placed. The labia may be sewn laterally if the view is obstructed.
The rectus fascia is usually harvested first to minimize vaginal bleeding. In adults, an 8- to 10-cm Pfannenstiel incision is made approximately 2 to 3 cm above the pubis. The subcutaneous tissue is cleared from the rectus fascia and a relatively scar-free area is selected. Even the most scarred and thickened rectus fascia is usually suitable as a sling. Incising parallel to the fibers, obtain a fascial sling approximately 8 to 10 cm in length with a center portion 1.5 to 2.0 cm wide, tapering the ends to 1 cm wide. Free the upper and lower fascial leaf from the rectus muscles superiorly and inferiorly for approximately 4 to 5 cm to allow a tension-free fascia closure. The sling sutures may be placed before or after transection. The size and type of suture used is a matter of personal preference but we currently use 1-0 polyglactin absorbable suture, which decreases postoperative suture pain and does not compromise durability. The sutures are placed perpendicular to the direction of the fibers approximately 0.5 cm from the ends incorporating all of the fibers in the bites.
The vaginal procedure begins by placing an Allis clamp midway between the bladder neck and the urethral meatus with traction placed superiorly. It is very important to maintain this traction throughout the vaginal procedure. Injectable saline is infiltrated beneath the vaginal epithelium over the proximal urethra to facilitate the dissection. A 3-cm midline incision is made over the proximal urethra and the initial vaginal dissection is performed with a scalpel or Church scissors, which allows one to quickly find the proper plane superficial to the white periurethral fascia. Damage to the underlying urethra and bladder is minimized when dissection proceeds in this plane. The dissection is facilitated by maintaining outward traction (toward the operator) on the developing vaginal flap and by maintaining the tips of the scissors on this flap at all times. Carry the dissection laterally and enter the retropubic space inferior to the ischium, at the level of the bladder neck, by perforating the endopelvic fascia using curved Metzenbaum scissors with tips pointed laterally and slightly superiorly. Blunt finger dissection should not be used to perforate the endopelvic fascia as bladder injury may occur. Once the endopelvic fascia is entered, gently advance the closed scissors laterally and slightly upward for 1 to 2 cm before opening widely. Gentle blunt finger dissection of the retropubic space superiorly to the rectus muscle is performed (Fig. 40-3). Through the abdominal incision, the lateral border of the rectus muscle is retracted medially to expose a defect just lateral to where the rectus muscle inserts onto the symphysis. Gentle dissection in this area allows safe and easy access into the retropubic space. If finger dissection of the retropubic space is difficult, as is sometimes the case after prior procedures, place the tips of Metzenbaum scissors directly on the posterior pubis and slowly advance them with constant pressure against the pubic periosteum. After this is completed, no tissue should be palpable between fingers inserted into the retropubic space from above and the vaginal incision below. If some intervening tissue is found at the level of the pelvic floor, penetration of that tissue is safe. If the tissue is higher than the pelvic floor, it is often the bladder attached to the posterior pubis. The bladder can be carefully dissected off the pubis by keeping the scissors on the back of the pubis at all times. A similar procedure is performed on the other side. Extensive retropubic space dissection is unnecessary and may lead to excessive bleeding or bladder injury. A Sarot or Crawford clamp is placed in the retropubic space from above and directed into the vaginal incision using manual guidance. The tip of the clamp should remain in contact with the pubic periosteum and under the vaginal operator’s finger at all times. After clamps have been passed bilaterally, cystoscopy is performed to ensure there has been no damage to the urethra or bladder. Each sling suture is pulled into the abdominal incision placing the sling under the urethra. Proper function and longevity of the sling does not depend on the sutures to hold tension indefinitely (since the sutures are absorbable) and thus it is critical that a good portion of the sling extend into the retropubic space to allow good fixation. One or two 3-0 absorbable sutures are placed through the edge of the sling and superficially through the periurethral fascia to secure it in place. The sling sutures are passed through the rectus fascia, directly above the retropubic “tunnel,” using a right angle clamp before the rectus fascia is closed. If a suprapubic tube needs to be placed (we do not recommend this), it is done under direct vision at this time. The vagina is closed with a running, locking 2-0 absorbable suture. The weighted speculum and all other instruments should be removed from the vagina. The sling sutures are gently pulled up to remove any slack and tied over the rectus. A shodded clamp can be used to hold tension on the untied sutures until the appropriate tension is obtained. The appropriate tension is the minimum amount required to stop urethral motion, which is tested by pulling on the urethral catheter. Also, one or two fingers should easily slide under the suture knot. If in doubt it is better to err on the side of too little tension. We do not place a vaginal pack before tying the sutures. We have not found it useful to judge how tight to pull the sling by visual assessment during cystoscopy nor by tightening the sling until leakage cannot be produced by compressing the bladder. In the situation where the patient does not void and permanent urinary retention is desired, increased tension can be applied. The skin is closed and a vaginal pack placed. When the abdominal and vaginal components are performed synchronously, the average operating time is 40 minutes with 50 ml average blood loss.
On postoperative day 1, the vaginal pack is removed; if the patient is ambulating well, the Foley catheter is removed. The patient performs clean intermittent catheterization after each void, or a minimum of every 4 hours if unable to void, until the postvoid residual is consistently under 60 ml. Patients are regularly discharged within 48 hours. Oral antibiotics are not routinely prescribed postoperatively. Patients should refrain from vigorous activities and sexual intercourse for 4 to 6 weeks to allow proper fixation of the sling.
When rectus fascia is used for the urethral sling, the most common complications include detrusor instability and urinary retention. Approximately 15% to 25% of patients will have residual urgency symptoms, with less than half demonstrating occasional urge incontinence. Less than 10% will develop new onset detrusor instability. In a recent report by O’Connell and colleagues, 26% of patients had residual urgency symptoms and less than half of this group had mild urge incontinence. In most cases, these symptoms are responsive to anticholinergic medications and will subside over a period of 3 to 6 months.
Persistent postoperative urinary retention, although believed to be a common complication, is not statistically more common after pubovaginal slings than after suspension procedures. In a recent series of 54 patients, no patient who could void preoperatively was in persistent retention postoperatively. McGuire and colleagues reported a 3% incidence of prolonged retention in one series.
Superficial wound infections occur in approximately 4% of patients and significant blood loss occurs in 1% to 2%. Wound infections have not resulted in sling failure. Although synthetic sling materials may be used, relatively high rates of infection and urethral erosion have been reported. Persistent postoperative pain is rare when absorbable suture is used. O’Connell and colleagues reported that no patient had to take analgesics chronically and no patient had a procedure to relieve pain.
In a recent series, 82% of patients were totally dry and another 11% had rare incontinence (once a week or less) for an overall 93% cured or significantly improved. Other long-term series have documented a greater than 80% cure and over 90% significantly improved rate. Residual stress incontinence usually responds very well to injectable agents such as collagen.
The pubovaginal fascial sling is the procedure of choice for treatment of females with urinary incontinence due to ISD. Even patients who had prior surgical failures can obtain excellent results with minimal morbidity, but such results are contingent on an accurate preoperative evaluation and careful placement of the sling at the proximal urethra without undue tension.