Overview of Stress Urinary Incontinence
Alexandra Dubinskaya
Jennifer T. Anger
Introduction
Approximately 1 in 3 women will experience stress urinary incontinence (SUI) in their lifetime.1 SUI affects a woman’s quality of life on many levels. Often, this condition is considered to be a normal part of aging, and, unfortunately, the general public is not widely aware of curative treatment options. This chapter describes the anatomy and the mechanisms underlying SUI. Conservative methods, considered to be an initial step in therapy, including pelvic floor muscle (PFM) exercises, incontinence devices, and pessaries are reviewed.
ANATOMY AND MECHANISM OF ACTION
Urinary continence in women is achieved by a combination of urethral constriction and urethral support. Several components are required to maintain continence: a healthy urethral mucosa and submucosa, functioning intrinsic urethral smooth muscles and striated sphincter, intact pudendal nerve function, and properly functioning PFM.5 The urethral mucosal lining produces secretions that increase surface tension. The submucosal layer contains an abundant amount of spongy vascular tissue that contributes to the closure pressure. The sphincteric mechanism controls the urine flow from the bladder to the urethra and contains two parts: an involuntary internal urethral sphincter and a voluntary external urethral sphincter. The internal sphincter consists of smooth muscle and is continuous with the detrusor muscle of the bladder. The external sphincter is located more distally and contains striated muscle: the compressor urethrae (the rhabdosphincter) that passes anteriorly and connects to the ischial rami and the urethrovaginal sphincter that surrounds both the vagina and urethra. In contrast to the compressor urethrae, which constricts just the urethra, the urethrovaginal sphincter constricts both the urethra and vagina. Innervation of the sphincteric mechanism comes from the S2 to S4 nerve roots. Control of the voluntary sphincter is provided by the pudendal nerve and nicotinic receptors. The involuntary sphincter is controlled by the autonomic nervous system via hypogastric nerves and alpha-1 receptors.6,7,8
The anatomic support of the urethra comes from the endopelvic fascia. Because the anterior vaginal wall is fused with the urethra and this connective tissue in turn attaches to the arcus tendinous fascia pelvis (ATFP) this forms the backstop by which the urethra is compressed during increases in intra-abdominal pressure.9 These attachments prevent the downward movement of the urethra. Damage to these structures is a significant predisposing factor for SUI (Fig. 23.1).10,11,12
According to the integral theory by Petros and Woodman,13 connective tissue laxity of the vagina and its supporting ligaments are the main cause of pelvic organ prolapse and SUI symptoms. This theory describes intimately dependable relationships between the pelvic organs and suspensory ligaments. According to this theory, the organs are storage containers (bladder stores urine, the bowel holds feces, and the uterus holds the fetus), each of them connected to the outside by a tubelike urethra, anus, or vagina. Muscles pull against the ligaments to close these tubes by compressing them and open them by stretching them. The bladder, vagina, and rectum are connected to the pelvic brim via ligaments, including the bulbourethral, cardinal/uterosacral, and ATFP. Weakening and damage to the suspensory system cause dysfunction that manifests as incontinence, retention, and/or organ prolapse.13,14 In addition, weakening of the pelvic floor causes the upper part of the urethra to relax and funnel into the bladder, which interferes with equal pressure transmission. This creates a situation in which bladder pressure is higher than urethral pressure, resulting in incontinence.15,16 This is the theoretical mechanism by which the Burch procedure (retropubic colposuspension) works. The main goal is to bring the urethra back into the pelvis and restore equal distribution of pressure. This is the same way that the traditional bladder neck sling works—by keeping the urethra closed with increased intra-abdominal pressures (Fig. 23.2).
 FIGURE 23.1 Sagittal view of lateral pelvis. Also shown are the ATFP, arcus tendineus fasciae rectovaginalis, and ischial spine. (Modified by J. Taylor from illustration by Lianne Krueger Sullivan. From Cundiff GW, Fenner D. Evaluation and treatment of women with rectocele: Focus on associated defecatory and sexual dysfunction. Obstet Gynecol 2004;104:1403-1421, erratum in Obstet Gynecol 2005;105:222, with permission.) |
De Novo Stress Urinary Incontinence
With worsening of vaginal prolapse, SUI tends to “improve” as the urethra becomes progressively “kinked” as the anterior vaginal wall prolapse (cystocele) worsens. Manual reduction of the prolapse or placement of a pessary will trigger the return of incontinence symptoms. This phenomenon is classically present in association with anterior prolapse; however, it can present in cases of severe apical or posterior compartment prolapse causing external compression of urethra.17 This phenomenon has been called latent, masked, or occult SUI. In the Colpopexy and Urinary Reduction Efforts (CARE) trial, women without SUI but with pelvic organ prolapse were randomly assigned to undergo abdominal sacrocolpopexy (ASC) alone or ASC with the addition of a Burch procedure in order to prevent possible de novo SUI postoperatively. They demonstrated a significant reduction in postoperative SUI with Burch (32% vs. 57.4%).18 A 7-year follow-up of this study, reported as eCARE, demonstrated that even
though efficacy decreased over time, urethropexy prevented SUI longer than no urethropexy.19
though efficacy decreased over time, urethropexy prevented SUI longer than no urethropexy.19
 FIGURE 23.2 The integral theory system. Four ligaments suspend the organs from above like a suspension bridge. The perineal body (PB) supports the organs from below. PCF, pubocervical fascia; RVF, rectovaginal fascia; PM, perineal membrane; CL, cardinal ligament; EUL, external urethral ligament. (Reprinted from Petros P. The Integral System. Cent European J Urol 2011;64[3]:110-119. doi:10.5173/ceju.2011.03.art1) |
Another multicenter randomized controlled trial (RCT), the Outcomes Following Vaginal Prolapse Repair and Mid Urethral Sling (OPUS) trial, randomized women with apical and/or anterior vaginal prolapse to vaginal repair (anterior colporrhaphy, paravaginal repair, colpocleisis, use of allograft, xenograft, or synthetic graft material) with or without a prophylactic midurethral sling placed at the time of surgery. The sling group had significantly lower rates of de novo postoperative SUI at 12 month follow-up (27.6% vs. 43%) but higher rates of adverse events.20,21
Performing prophylactic continence procedures, such as a midurethral sling, on preoperatively continent patients remains controversial. It is important to evaluate patients for the presence of occult stress incontinence before surgery, in order to best predict the need for concomitant correction with a midurethral sling. To best assess this, prolapse reduction can be performed using a variety of methods with different rates of success in detection of de novo incontinence: manually 16% (19 of 122), pessary 6% (5 of 88), swab 20% (32 of 158), and speculum 30% (35 of 118).22 The goal of the prolapse reduction is to simulate the prolapse repair and assess the risk for developing SUI postoperatively. Patients can wear a pessary at home and assess for SUI, or urodynamics can be performed in the office with the prolapse reduced. Of note, it is important to not obstruct the urethra because this would give an inaccurate result.
TREATMENT
The degree of SUI can vary from mild, with urinary leakage during rigorous activity (playing sports, exercising, sneezing, laughing, coughing, or lifting) to moderate and severe leakage, with loss of larger volumes of urine that occurs with low-impact movements such as standing up, walking, or bending over.
Body mass index (BMI) plays an important role in the development and progression of SUI. Excess weight increases intra-abdominal pressure, bladder pressure, and urethral mobility. In fact, Gleicher et al.23 found the prevalence of SUI to be significantly higher in women with BMI >30 compared to those with BMI <30 (63.4% vs. 36.5%, respectively, P < .001). Several epidemiologic studies have demonstrated that an increase in BMI by five units is associated with a 20% to 70% increase in the risk of developing incontinence.24,25 The opposite is true, weight loss (with exercise or bariatric surgery) improves SUI symptoms.26 In fact, Subak et al. demonstrated that weight loss of 8.0% of body weight over the 6 months period decreased the frequency of SUI episodes by 47%.24
As with most pelvic floor disorders, the treatment strategy should progress from more conservative to less conservative. Depending on the level of symptom bother, patients should first be provided with education on avoiding triggering activities, emptying the bladder before exercise and learning to voluntarily contract the PFMs in situations that would normally cause urinary leakage, such as cough or sneeze.
Pelvic Floor Muscle Therapy
Pelvic floor muscle therapy (PFMT) is training of the levator ani muscles. These include the iliococcygeus, pubococcygeus, and puborectalis muscles. The goal of PFMT exercises is to improve the strength and function of the pelvic floor. The levator ani muscles are predominantly composed of slow-twitch/type I fibers; only one-third of the levator ani muscles fibers are fast-twitch/type II fibers. The slow-twitch muscles provide baseline tonic activity and contribute to the compression of the urethra against the pubic bone. This results in passive continence. The fast-twitch muscle fibers provide continence in the setting of a sudden increase in intra-abdominal pressure. The thickness of the levator ani muscles correlates with their strength.27
One of the most common factors adversely impacting pelvic muscle strength is vaginal delivery. In a study of postpartum women who underwent vaginal deliveries, MRI series showed disruption in levator ani muscles.28 Pelvic muscle strength was significantly affected by vaginal delivery and also by a trial of labor, even if women ultimately underwent cesarean delivery.29,30
PFM function can be determined by both their tone at rest and the strength of voluntary contractions. Strength is defined as strong, weak, or absent. There are several grading methods to quantify the strength of the PFMs. The Modified Oxford scale assigns grades of 0 (no discernable PFM contractions) to grade 5 (strong PFM contraction) (Table 23.1) The Brink assessment scale evaluates three PFM contraction variables: vaginal pressure or muscle force, elevation or vertical
displacement of the examiner’s fingers, and the duration of contraction (Table 23.2). Each of these variables is rated on a 4-point scale and summed together to obtain total score ranging from 3 to 12. Tips on how to identify an ideal PFM contraction listed in Table 23.3.
displacement of the examiner’s fingers, and the duration of contraction (Table 23.2). Each of these variables is rated on a 4-point scale and summed together to obtain total score ranging from 3 to 12. Tips on how to identify an ideal PFM contraction listed in Table 23.3.
TABLE 23.1 Modified Oxford Grading Scale of Pelvic Floor Muscle Contraction | ||||||||||||||||
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TABLE 23.2 Brink Scoring System of Pelvic Floor Muscle Contraction | |||||||||||||||||||||||
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It is important for providers to assess a patient’s PFM strength and ability to recruit the correct muscles while performing PFM exercises. These exercises, known as Kegel exercises, are simple to perform, noninvasive, and are an effective first-line therapy for SUI.31 In a recent Cochrane review of 31 trials that studied 1,874 women, women in the PFM training groups were more likely to report cure compared to the no-treatment groups.32,33
The key to PFMT effectiveness is daily compliance. Different options to promote compliance have been suggested: setting a reminder on one’s phone, performing exercises in the car while stopped at a stop sign, and weekly sessions with a nurse practitioner and/or pelvic floor therapist in the office. There are many new commercial devices available online that facilitate performance of the exercises, with some of them providing feedback about the strength of the contractions and correct muscle use. In fact, the use of mobile apps for PFM training have shown effectiveness and relevant improvement in women with SUI.34 PFM exercise is also a great option for muscle recovery in the postpartum period.35 However, women with more severe and long-standing leakage are more likely to benefit from surgical treatment, and extensive trials of conservative management may be futile in these women.
TABLE 23.3 Tips on How to Identify an Ideal Pelvic Floor Muscle Contraction | ||||||||||
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Biofeedback
Biofeedback is a technique that involves the use of visual or auditory feedback to help a woman gain control over her PFM. Biofeedback is achieved with one of several methods: electromyography, which monitors the electrical activity of muscles during contraction and relaxation; manometry, which measures pressure generated by muscle contractions; direct palpation by a provider with verbal feedback; or commercial devices with built-in apps that provide feedback. Considered by many to be the father of PFM training, Arnold Kegel implemented a vaginal perineometer as a biofeedback modality for SUI in 1956. He reported a 90.6% success rate with this technique and claimed that correct performance of PFM exercise is crucial to success.36 Biofeedback use in PFM training has also demonstrated efficacy and improvement of SUI in more recent trials.37,38,39
For those women who have weak PFMs or unable to identify the correct muscle group, adding electrical
stimulation to the vaginal probe used for biofeedback might facilitate muscle identification and enhance exercise performance. However, electrical stimulation in women capable of performing muscle contractions provides no additional benefits.40 Electrical stimulation should be avoided in pregnancy, vaginal infection, an open vaginal or vulvar wound, and recent (within 6 weeks) pelvic surgery.41 Another option to help with identification of PFMs is a real-time ultrasound. This biofeedback technique helps to visualize the “lift” component of the PFM contraction. Although this tool can be added during exercise instructions, limited studies assess the value of real-time ultrasound versus PFM exercise alone.
stimulation to the vaginal probe used for biofeedback might facilitate muscle identification and enhance exercise performance. However, electrical stimulation in women capable of performing muscle contractions provides no additional benefits.40 Electrical stimulation should be avoided in pregnancy, vaginal infection, an open vaginal or vulvar wound, and recent (within 6 weeks) pelvic surgery.41 Another option to help with identification of PFMs is a real-time ultrasound. This biofeedback technique helps to visualize the “lift” component of the PFM contraction. Although this tool can be added during exercise instructions, limited studies assess the value of real-time ultrasound versus PFM exercise alone.
Vaginal Inserts
The idea behind the insertion of vaginal cones is to provoke PFM contraction when inserted into vagina. The original set of cones was introduced in 1985 and contained nine different cones with weight between 20 and 100 g.42 These devices are best used in women with mild SUI and those able to accommodate the device without discomfort. The training starts with the heaviest insert that a patient can retain for 1 minute twice a day. The time holding the insert progressively increases to 15 minutes twice a day. After that, the patient progresses to a higher insert weight. There are commercially available inserts with different weight sets and with extra options for vibration that can be purchased to facilitate at-home PFM training. Most of the trials done with vaginal cones are small. There is a lack of evidence that weighted vaginal cones are better than no active treatment. According to a Cochrane systematic review, cones plus PFMT has not shown improvement over cones alone or PFMT alone in women with SUI.43
Pessary
The pessary has been in use for centuries. Most commonly, pessaries are used for pelvic organ prolapse. However, there are pessaries with a specially designed “knob” (additional anterior-posterior width that is placed at the urethrovesical junction) that are predominantly used for SUI. The most commonly used pessaries of this type are a “ring with knob” and “incontinence dish.”
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