Modern Management of Women with Stress Urinary Incontinence: Part 2
Surgical Procedures
More than 100 surgical techniques have been described for the correction of SUI and more continue to be developed. From this large number, it is obvious that no “perfect” procedure exists. If a surgical procedure is to be performed, the patient should be properly informed of its estimated risks and benefits, including expected postoperative course, potential complications, and treatment for the complications. The decision should take into account patient preferences as well as the experience and skill of the surgeon.
The surgical procedures for treating SUI have developed in pace with changing understanding of the pathophysiology of SUI. In the 1960s, Enhorning21 proposed that SUI was due to descent of the bladder neck and the proximal urethra, which prevents equal transmission of intrabdominal pressure to the bladder and urethra, causing urinary leakage with stress maneuvers. In 1980, McGuire22 observed patients who had undergone previous continence surgery with recurrent SUI. These patients had a fixed bladder neck with SUI. Urodynamic studies revealed low abdominal leak point pressures, which he hypothesized to be due to a weak urethral sphincter or intrinsic sphincter deficiency (ISD). In the 1990s, Delancey23 hypothesized that continence is dependent on a stable anterior vaginal wall, which serves as a platform against which the urethra can be compressed during increases in intra-abdominal pressure. This has been termed the “hammock hypothesis.” Finally, Petros and Ulmsten24 described the “integral theory,” where the pubourethral ligaments are essential in the maintenance of continence.
At this time, general consensus is that continence is dependent on fascial connections and support of the bladder neck and urethra as well as proper functioning of the urethral sphincter.25 The manifestation of SUI may not be due to one factor but rather to a combination of factors known and unknown. Ultimately, the goals of any surgery are to restore the urethra to its proper position and to stabilize it, increase or improve intrinsic urethral closure, or both.
Incontinence Surgery
Retropubic suspensions. Retropubic bladder suspensions aim to elevate and support the bladder neck and proximal urethra to prevent funneling and align the bladder neck in a posterior-superior position in relation to the pubic symphysis in order to increase urethral outflow resistance. The two most common techniques are the Marshall-Marchetti-Krantz (MMK) procedure, popularized in the late 1940s and early 1950s, and the Burch procedure described in 1961. The MMK is described as the elevation and fixation of the paraurethral tissue to the posterior periosteum of the pubis symphysis.26 It is believed this works by stabilizing the urethra-vesical junction in an endopelvic position. Short-term results were good with greater than 80% subjective continence rates; however, with longer follow-up, continence rates decreased. Nearly 80% of patients were dry at 6 months, but this number decreased to 33% at 15 months.27
The Burch procedure involves fixation of the paravaginal tissue supporting the urethra to Cooper’s ligament or the ilio-pectineal line.28 This procedure has undergone modification over the years — the most significant, the Tanagho modification, involves no attempt to bring the vaginal wall all the way to Cooper’s ligament. Instead, a gap is left with free suture between the ligament and vaginal wall.29 The Burch procedure has shown good short-term and long-term success. One study showed nearly 90% cure rates with a mean follow-up of 1.5 years and 75% cure rates with a mean follow-up of 4.5 years.30 Subjective cure rates are nearly 70% with almost 14-year follow-up.31
Typically, both procedures are performed through low transverse incisions unless they are performed concurrent with another abdominal procedure. With the trend toward more minimally invasive techniques, the Burch procedure has been mimicked through a laparoscopic approach. This approach may take longer and requires increased surgical skill, but if it duplicates the same suture placement as the open procedure, the results should be equivalent. The short-term results of the laparoscopic Burch procedure have been comparable to the open procedure,32 but the long-term results are not as good.33 Complications specific to retropubic suspensions include postoperative voiding dysfunction, de novo urgency, and vaginal prolapse, especially apical and posterior wall prolapse. In the case of the MMK, a potential problem with osteitis pubis and osteomyelitis exists.34
Urethral bulking agents. This therapy, although originally advocated for the treatment of SUI without hypermobility or ISD, has been more recently used in SUI with or without hypermobility. The treatment consists of injecting bulking agents at the level of the proximal urethra. The goal is to improve coaptation of the urethra; therefore, increasing urethral closure pressure without leading to an increased voiding pressure.
Bulking agents. Although a number of agents have been used, only two are currently FDA approved. One is glutaraldehyde cross-linked bovine collagen (Contigen, C.R. Bard, Covington, Ga.) and the other is pyrolytic carbon-coated zirconium beads (Durasphere, Boston Scientific, Natick, Mass.). Used since 1993, Contigen is a bovine collagen that is cross-linked with glutaraldehyde to resist antigencity and collagenase degradation. Advantages of using collagen include its long history of use, ease of administration, and lack of migration. Disadvantages include the need to undergo a skin test before use because up to 4% of patients may have an allergic reaction due to its bovine origin35; its degradation also is a consideration.
Durasphere, approved in 1999, is composed of pyrolytic carbon-coated zirconium beads in a carrier gel. Because of the synthetic nature of this product, it is not reactive; therefore, no skin testing needs to be performed. It is not degraded and the large size of the beads should prevent their migration form the injection site, a problem with previously tried substances such as polytetrafluoroethylene. One disadvantage is that due to the composition of the material, it may be more difficult to administer than Contigen. Currently, a number of other agents are being used outside of the US — some will be undergoing trial and may be future options for surgeons.
Procedure. The procedure can be performed either transurethrally or periurethrally. In the transurethral approach, a cystoscopic needle is placed through a cystoscope, advanced into the proximal urethra, and the bulking material is injected. Careful needle placement is needed to minimize extravasation of the bulking agent. This is done by creating a long tunnel while simultaneously preventing the needle from moving too superficially which may cause rupture of the urethral mucosa. Injections can be performed at the 5 o’clock and 7 o’clock positions of the urethra or until good coaptation is achieved. Periurethral injections are an alternative method. In this case, either a spinal needle or special angled needle is used to inject the material alongside the urethra. A cystoscope is placed in the urethra at the time of injection so coaptation can been seen. Either method can be effective and depends on the preference of the surgeon. In a study comparing Durasphere to Contigen, improved continence at 1 year was 80.3% and 69.1%, respectively.36
The injection of bulking agents can be performed in the office under local anesthesia. This therapy can be performed on almost any patient as long as she is infection-free, has a pliable urethra into which the material can be injected, and lacks hypersensitivity to the agent. Overall success rates for collagen may be about 80%, with 40% cured and 40% improved. The efficacy generally decreases after 1 to 3 years.37,38 Similar efficacy appears to be achieved in patients both with and without hypermobility. Results using Durasphere and Contigen are similar.36 The potential complications include de novo urgency and urinary retention which which may last a few days.39 Ultimately, because of the minimally invasive nature of the procedure and the ability to perform this in the office under local anesthetic, this procedure can essentially be an option offered to every patient. However, immediate repeat injections as well as future injections maybe necessary.
Pubovaginal sling. Pubovaginal slings can be used to treat SUI caused by hypermobility and/or ISD.40 Their use has been described since the early 1900s; numerous modifications subsequently have been made. Although typically autologous rectus fascia or fascia lata has been used for the sling, many other types of materials have been tried, including allografts, xenografts, and synthetics (absorbable and nonabsorbable). Methods for anchoring the sling also have varied widely, including use of sutures tied above the rectus fascia, bone anchors, and most recently, no fixation at all. Whether the sling should be placed at the bladder neck/proximal urethra or mid-urethra is debatable.22,24
The “traditional” fascial sling upon which most modern day slings are based was described by Aldridge in 1942.41 He used autologous rectus fascial strips that remained attached to the anterior abdominal to wall to support the urethra as a salvage operation for women who had failed previous surgery. McGuire and Lyton42 are credited with the modern reemergence of the pubovaginal sling. The procedure is typically performed via an abdominal and vaginal approach. A strip of abdominal rectus fascia is harvested and nonabsorbable sutures are placed at the ends. The retropubic space is entered, the endopelvic fascia is perforated, and suture carriers are brought from a suprapubic location out a suburethral vaginal incision. The sutures on the sling are then passed via the suture carries above the fascia, the sutures are tied above the rectus fascia, and all incision sites are closed.
Although suburethral fascial slings have been most often used as secondary procedures to treat recurrent SUI after previous bladder neck surgery, mean short-term cure rates are about 85% with durable results.43 In one study, 257 women with a mean follow-up of 51 months maintained a cure rate of >80%. The complication rate was 4%.44 The advantages of autologous fascial slings include the use of native tissues; thus, minimizing the risk of infection and erosion and improving long-term results. Disadvantages include longer operative times, increased hospitalization, and time to recovery due to the abdominal incision and necessary dissection.
Newer slings aim to maintain or improve continence results and decrease morbidity. The most recent variations on the sling procedure include the popular and minimally invasive tension-free vaginal tape (TVT). This approach involves the placement of a strip of nonabsorbable polypropylene mesh under the mid-urethra and behind the pubic symphysis in a tension-free manner; the mesh is attached to trochars. The procedure can be performed in an antegrade or retrograde manner depending on the preference of the surgeon. The tape is believed to reinforce the pubourethral ligaments and suburethral vaginal wall, causing dynamic urethral resistance during stress maneuvers. Because of the tension-free placement of tape, postoperative voiding dysfunction is rare (<5%).45
The long-term results of using TVT for SUI indicate positive outcomes. In a multicenter trial, Nilsson and colleagues46 found that using this approach 85% of patients were cured, 10.6% improved, and 4.7% failed. Follow-up in this study was a median of 56 months. Complications from TVT include vascular and bowel injury, urinary retention, mesh erosion and infection, de novo urgency, and bladder perforation.
New innovations. Because of the ease of use, minimally invasive nature, and relatively low complication rates, a number of similarly produced products have come to market with subtle differences. The most recent and novel sling to be developed is the transobturator sling; it also utilizes a piece of synthetic mesh but rather than passing it through the retropubic space, it is placed through the medial portion of the obturator foramen to the suburethral location. The theoretic advantages are decreased chance of vascular, bowel, and bladder injury, as well as possible decreased de novo urgency. One recent study comparing the transobturator approach (n = 30) to the TVT (n = 31) shows similar efficacy at 1 year, with cure rates >80%.47 Longer follow-up will be necessary to determine if the results are durable and the purported advantages are true.
Artificial urinary sphincter. The artificial urinary sphincter (AUS) is a mechanical device (AMS) consisting of three components: a cuff that encircles the urethra, a reservoir in the retropubic space, and pump for activation/deactivation placed in the labia. The device is typically in the “activated” state — that is, the cuff is inflated, compressing the urethra. When the patient feels the desire to void, she is able to manipulate the pump, causing fluid to move from the cuff to the reservoir to open the urethra, allowing her to void. The cuff will automatically refill and compress the urethra to maintain continence.
This procedure has been routinely used in men with postprostatectomy incontinence; its use in women has been limited.48 The AUS can be placed via a transabdominal or transvaginal approach. Although a potentially good option for women with severe SUI who have failed other therapies, not all women are candidates for AUS. They must have adequate understanding of the device as well as the dexterity to use the pump, normal bladder compliance, and ideally, normal detrusor function to completely empty. This is typically not a widespread procedure because it may be technically difficult to place. Potential downsides include infection, mechanical failure, and erosion rates. However, this may be a viable option for the patient who has failed all other treatments.49
Conclusion
Stress urinary incontinence is a common problem affecting millions of women. As increasing dialogue regarding incontinence occurs, both patients and physicians will be more likely to address the subject. At this time, a variety of effective SUI treatment options are available. The quality of these options is destined to improve as understanding of the disease process grows and critical evaluation of current treatments is undertaken.
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