Although definitions are inconsistent, anal incontinence (AI) is most commonly defined as an involuntary loss of flatus, liquid, or solid stool that causes a social or hygienic problem (Abrams, 2005; Haylen, 2010). The definition of AI includes incontinence of flatus, whereas that of fecal incontinence (FI) does not.
Despite acceptance of these by healthcare professionals, one survey observed that only 30 percent of nearly 1100 community-dwelling women with FI had heard the term “fecal incontinence,” and 71 percent preferred the term “accidental bowel leakage” (Brown, 2012). Thus, at a recent consensus workshop, this latter more patient-centered term was suggested for use with patients (Bharucha, 2015).
AI can lead to poor self-image and isolation, and the social and quality-of-life effects of AI are significant (Johanson, 1996). Additionally, AI increases the likelihood that an older patient will be admitted to a nursing home rather than cared for at home (Grover, 2010).
Anal incontinence is common, and rates among men and women are similar (Madoff, 2004b; Nelson, 2004). In one National Health and Nutrition Examination Survey (NHANES), FI was also not significantly associated with race or ethnicity, education level, income, or marital status (Whitehead, 2009). Although all age groups may be affected, the AI prevalence increases with age and may reach 46 percent in older, institutionalized women (Nelson, 1998). Using data from NHANES that incorporated years 2005 through 2010, investigators noted that the prevalence of FI in women approximated 9 percent (Nygaard, 2008; Wu, 2014). Similarly, the estimated prevalence of FI in noninstitutionalized U.S. adults was 8.3 percent (18 million). Of these individuals, liquid stool incontinence was noted in 6.2 percent, mucus in 3.1 percent, and solid stool in 1.6 percent (Whitehead, 2009). The prevalence of FI increased from 2.6 percent in those aged 20 to 30 years and rose to 15.3 percent in subjects aged 70 years or older.
Normal defecation and anal continence are complex processes that require: (1) a competent anal sphincter complex, (2) normal anorectal sensation, (3) adequate rectal capacity and compliance, and (4) conscious control. Logically, mechanisms responsible for FI include anal sphincter and pelvic floor weakness, reduced or increased rectal sensation, reduced rectal capacity and compliance, and diarrhea (Bharucha, 2015). In many patients these factors may be additive, and thus no single physiologic measure is consistently associated with FI.
Essential contributors to fecal continence include the internal and external anal sphincters and the puborectalis muscle (Figs. 38-9 and 38-21). Of these, the internal anal sphincter (IAS) is the thickened distal 3- to 4-cm longitudinal extension of the colon’s circular smooth-muscle layer. It is innervated by the autonomic nervous system and provides 70 to 85 percent of the anal canal’s resting pressure (Frenckner, 1975). As a result, the IAS contributes substantially to the maintenance of fecal continence at rest.
The external anal sphincter (EAS) consists of striated muscle and is primarily innervated by somatic motor fibers that course in the inferior rectal branch of the pudendal nerve (Fig. 25-1A). The EAS provides the anal canal’s squeeze pressure and is mainly responsible for maintaining fecal continence when continence is threatened. At times, squeeze pressure may be voluntary or may be induced by increased intraabdominal pressure. In addition, although resting sphincter tone is generally attributed to the IAS, the EAS maintains a constant state of resting contraction and may be responsible for approximately 25 percent of anal resting pressure. During defecation, however, the EAS relaxes to allow stool passage.
Innervation of the anal sphincter complex. A. The external anal sphincter is innervated by the pudendal nerve. B. Innervation of the female pelvic floor muscles from direct branches of S3-S5.
The puborectalis muscle is part of the levator ani muscle group and is innervated from its pelvic surface by direct efferents from the third, fourth, and fifth sacral nerve roots (Fig. 25-1B) (Barber, 2002). Although the suggestion is controversial, it may also be innervated from its perineal surface by the inferior rectal branch of the pudendal nerve. Its constant tone contributes to the anorectal angle, which aids in preventing rectal contents from entering the anus (Fig. 38-10). Similar to the EAS, this muscle can be contracted voluntarily or in response to sudden increases in abdominal pressure.
The role of the puborectalis in maintaining stool continence remains unclear. However, it is best appreciated in women who remain continent of solid stool despite absence of the anterior arch of the external and internal sphincters, as can be seen in those with chronic fourth-degree lacerations (Fig. 25-2). With normal puborectalis relaxation, evacuation is generally aided by the better longitudinal alignment of the rectoanal lumen. Conversely, paradoxical contraction of the puborectalis muscle during defecation may lead to impaired evacuation. Moreover, atrophy of this muscle has been associated with FI (Bharucha, 2004).
Chronic fourth-degree laceration with complete absence of the perineal body and the anterior portion of external anal sphincter (cloacal-like deformity). Skin dimples at 3 and 9 o’clock (arrows) indicate sites of retracted ends of the external anal sphincter.
Innervation to the rectum and anal canal is derived from the inferior hypogastric nerve plexus that contain sympathetic and parasympathetic components and by intrinsic nerves present in the rectoanal wall (Fig. 38-13, p. 806). In addition, the inferior rectal branch of the pudendal nerve conveys sensory input from the lower anal canal and the skin around the anus. Sensory receptors within the anal canal and pelvic floor muscles can detect the presence of stool in the rectum and the degree of distention. Through these neural pathways, information regarding rectal distention and rectal contents can be transmitted and processed and the action of the sphincteric musculature coordinated.
The rectoanal inhibitory reflex (RAIR) refers to the transient relaxation of the IAS and contraction of EAS induced by rectal distention when stool first arrives in the rectum. This reflex is mediated by the intrinsic nerves in the anorectal wall and allows the sensory-rich upper anal canal to come in contact with or “sample” the rectal contents (Whitehead, 1987). Specifically, sampling refers to the process whereby the IAS relaxes, often independently of rectal distention, allowing the anal epithelium to ascertain whether rectal contents are gas, liquid, or solid stools (Miller, 1988).
Following integration of this neural information, defecation can ensue in the appropriate social setting. Alternatively, if required, defecation can generally be postponed, as the rectum can accommodate its contents and the EAS or puborectalis muscle or both can be voluntarily contracted. However, if rectal sensation is impaired, contents may enter the anal canal and may leak before the EAS can contract (Buser, 1986).
Evaluation of the RAIR may clarify the underlying etiology of AI. This reflex is absent in those with congenital aganglionosis (Hirschsprung disease) but preserved in patients with cauda equina lesions or after spinal cord transection (Bharucha, 2006).
Rectal Accommodation and Compliance
Following anal sampling, the rectum can relax to admit the increased rectal volume in a process known as accommodation. The rectum is a highly compliant reservoir that permits stool storage. As rectal volume increases, an urge to defecate is perceived. If this urge is voluntarily suppressed, the rectum relaxes to continue stool accommodation. A loss of compliance may decrease the ability of the rectal wall to stretch or accommodate, and as a result, rectal pressure may remain high. This may place increased demands on the other components of the continence mechanism such as the anal sphincter complex.
Rectal compliance can be calculated by measuring the sensitivity to and maximal volume tolerated from a fluid-filled balloon during anorectal manometry. Rectal compliance may be decreased in those with ulcerative and radiation proctitis. In contrast, increased compliance may be noted in certain patients with constipation, potentially signaling a megarectum.
Abnormal defecation develops if any of the just-described components of anal continence are altered. Logically, causes of AI and defecatory disorders are diverse and are likely multifactorial (Table 25-1).
TABLE 25-1Risk Factors for Fecal Incontinence ||Download (.pdf) TABLE 25-1 Risk Factors for Fecal Incontinence
|Increasing parity ||Anal sphincter damage |
|Medical conditions |
|Diabetes mellitus |
| Urogynecologic |
|Urinary incontinence ||Pelvic organ prolapse |
| Gastrointestinal |
|Anal abscess |
| Neuropsychiatric |
|Spinal cord lesion |
Nerve stretch injury
In younger, reproductive-aged women, the most common association with AI is vaginal delivery and damage to the anal sphincter muscles (Snooks, 1985; Sultan, 1993; Zetterstrom, 1999). This damage may be mechanical or neuropathic and can result in fecal and flatal incontinence at an early age. Interestingly, the incidence of FI following vaginal delivery has declined from 13 percent of primiparous women two decades ago to 8 percent in more recent series (Bharucha, 2015). This may reflect changes in obstetric practices that include decreased use of instrumented vaginal delivery and more restricted episiotomy use.
Rates of sphincter tear during vaginal births in the United States range from 6 to 18 percent (Fenner, 2003; Handa, 2001). In one study of primiparas delivered at term, at both 6 weeks and 6 months postpartum, women who sustained anal sphincter tears during vaginal delivery had twice the risk of FI and reported more severe FI compared with women who delivered vaginally without evidence of sphincter disruption (Borello-France, 2006). In contrast, a retrospective study of 151 women with diverse obstetric histories who delivered 30 years previously reported that women with a prior sphincter disruption were more likely to have “bothersome” flatal incontinence but were not at increased risk for FI compared with women who had an isolated episiotomy or those who underwent cesarean delivery (Nygaard, 1997). Thus, other mechanisms associated with pregnancy and with aging may contribute to AI regardless of delivery mode or anal sphincter disruption. Importantly, cesarean delivery minimizes the risk of anatomic anal sphincter injury, but it does not universally protect against later AI. The National Institutes of Health (NIH) (2006) consensus conference on cesarean delivery on maternal request concluded that evidence was insufficient to support a practice of elective cesarean delivery for the prevention of pelvic floor disorders, including FI.
Few epidemiological studies have evaluated the risk factors for FI in the community. That said, underlying bowel disturbances, particularly diarrhea; the symptom of rectal urgency; and burden of chronic illness, are the strongest independent risk factors for FI (Bharucha, 2015). Inflammatory bowel conditions, especially with chronic diarrhea, are another common risk. Liquid stool is more difficult to control than solid, and thus FI may develop even if all components of the continence mechanism are grossly intact. Alternatively, chronic constipation with straining to defecate may damage the muscular and/or neural components of the sphincter mechanism. Similarly, other neuromuscular injury to the puborectalis and/or anal sphincter muscles, such as that associated with pelvic organ prolapse, may lead to AI.
Radiation therapy involving the rectum can result in poor compliance and loss of accommodation. Also, nervous system dysfunction in those with spinal cord injury, back surgery, multiple sclerosis, diabetes, or cerebrovascular accident may lead to poor accommodation, loss of sensation, impaired reflexes, and myopathy. Finally, loss of rectal sensation and decreased squeeze sphincter pressures can be seen with normal aging. One study suggests that even asymptomatic older nulliparous women have anal sphincter neurogenic injury, which partly explained weak anal squeeze pressures (Bharucha, 2012).
There is no current consensus on how best to screen for FI. Proposed barriers include poor patient understanding of the term FI, embarrassment, a belief that FI is a normal part of aging, confusion as to whom they might discuss the problem with, priority of other medical conditions, and unfamiliarity or pessimism regarding treatment options (Bharucha, 2015). In one study, less than one third of patients with FI had disclosed this to a provider (Johanson, 1996). In another that evaluated women presenting for benign gynecologic care, only 17 percent with FI were asked about the symptom by their health care provider (Boreham, 2005).
In contrast to urinary incontinence, no FI classification approach is widely accepted. However, the type (urge, passive, or mixed), etiology, and severity of FI provide some basis to categorize FI. A complete history and physical examination evaluates these prior to treatment planning and often identifies correctable problems.
To the patient, relevant questions are posed regarding incontinence duration and frequency, stool consistency, timing of incontinent episodes, use of sanitary protection, and incontinence-related social impairment. Additionally, risk factors noted in Table 25-1 are sought. Importantly, urge-related AI is differentiated from incontinence without awareness, as these may be associated with different underlying pathologies. For example, urgency without incontinence may reflect inability of the rectal reservoir to store stool rather than a sphincteric disorder.
To gather historical data, validated questionnaires, stooling diaries, and the Bristol Stool Scale are objective options. Of these, a patient diary of stool habits is commonly used in research, but its utility is often limited by poor patient adherence. Alternatively, questionnaires reduce patient recall bias and help standardize AI scores. Several incontinence-scoring systems provide objective measure of a patient’s degree of incontinence. Four commonly used symptom severity scores are the Pescatori Incontinence Score; Wexner (Cleveland Clinic) Score; St. Marks (Vaizey) Score; and the Fecal Incontinence Severity Index (FISI) (Tables 25-2 and 25-3) (Jorge, 1993; Pescatori, 1992; Rockwood, 1999; Vaizey, 1999). All of these incorporate the type and frequency of leakage. Of these, the Vaizey Score and the FISI include symptom weighting. The inclusion of patient-assigned severity scores increases the utility of the FISI compared with other scales. The ability of the Vaizey Score to incorporate a component of fecal urgency makes this scale desirable in certain clinical trials.
TABLE 25-2Fecal Incontinence Severity Index ||Download (.pdf) TABLE 25-2 Fecal Incontinence Severity Index
| ||Two or MoreTimes Daily ||Once Daily ||Two or MoreTimes Weekly ||Once Weekly ||1–3 TimesMonthly ||Never |
| Gas ||▫ ||▫ ||▫ ||▫ ||▫ ||▫ |
| Mucus ||▫ ||▫ ||▫ ||▫ ||▫ ||▫ |
| Liquid stool ||▫ ||▫ ||▫ ||▫ ||▫ ||▫ |
| Solid stool ||▫ ||▫ ||▫ ||▫ ||▫ ||▫ |
TABLE 25-3St. Marks (Vaizey) Incontinence Score ||Download (.pdf) TABLE 25-3 St. Marks (Vaizey) Incontinence Score
| ||Never a ||Rarely b ||Sometimes c ||Weekly d ||Daily e |
|Incontinence for solid stool ||0 ||1 ||2 ||3 ||4 |
|Incontinence for liquid stool ||0 ||1 ||2 ||3 ||4 |
|Incontinence for gas ||0 ||1 ||2 ||3 ||4 |
|Alteration in lifestyle ||0 ||1 ||2 ||3 ||4 |
| || ||No ||Yes || || |
|Need to wear a pad or plug ||0 ||2 || || |
|Taking constipating medicines ||0 ||2 || || |
|Lack of ability to defer defecation for 15 minutes ||0 ||4 || || |
In addition to symptom severity, the patient’s quality-of-life decline from AI is also characterized. The validated fecal incontinence quality-of-life (FI-QOL) questionnaire is a 29-item tool designed to estimate associated worsening lifestyle, coping behavior, depression/self-perception, and embarrassment (Table 25-4) (Rockwood, 2000). Other quality-of-life scales available include the Modified Manchester Health Questionnaire and the Gastrointestinal Quality of Life Index (Kwon, 2005; Sailer, 1998). These validated tools may be used diagnostically and also following treatment to determine response.
TABLE 25-4Fecal Incontinence Quality of Life Scale Composition ||Download (.pdf) TABLE 25-4 Fecal Incontinence Quality of Life Scale Composition
| Scale 1: Lifestyle || |
|I am afraid to go out ||I avoid traveling |
|I avoid visiting friends ||I avoid traveling by plane or train |
|I avoid many things I want to do ||I avoid staying overnight away from home |
|I plan my schedule around my bowel pattern ||I avoid going out to eat |
|It is difficult for me to get out and do things ||I limit how much I eat before I go out |
| Scale 2: Coping/Behavior || |
|I feel I have no control over my bowels ||I have sex less often than I would like to |
|I worry about bowel accidents ||I worry about not reaching the toilet in time |
|The possibility of bowel accidents is always on my mind || |
|Whenever I go someplace new, I specifically locate where the bathrooms are |
|I try to prevent bowel accidents by staying very near a bathroom |
|I can’t hold my bowel movement long enough to get to the bathroom |
|Whenever I am away from home, I try to stay near a restroom as much as possible |
| Scale 3: Depression/Self-perception || |
|In general, how would you say your health is? ||I feel different from other people |
|I am afraid to have sex ||I enjoy life less |
|I feel depressed ||I feel like I am not a healthy person |
|During the past month, have you felt so sad, discouraged, hopeless, or had so many problems that you wondered if anything was worthwhile? |
| Scale 4: Embarrassment || |
|I leak stool without even knowing it || |
|I worry about others smelling stool on me || |
|I feel ashamed || |
Last, the validated Bristol Stool Scale is often selected to determine a patient’s usual stool consistency (Lewis, 1997). This scale contains seven descriptions of stool characteristics and pictures of each stool type (Fig. 25-3) (Degen, 1996). Such stool consistency categorization correlates with objective measures of whole-gut transit time (Heaton, 1994).
Bristol Stool Scale. Stools are categorized by their shape and texture. (Reproduced with permission from Lewis SJ, Heaton KW: Stool form scale as a useful guide to intestinal transit time. Scand J Gastroenterol 1997 Sep;32(9):920–924.)
This begins with careful inspection of the anus and perineum to identify stool soiling, scars, perineal body length, hemorrhoids, anal warts, rectal prolapse, dovetail sign, or other anatomic abnormalities (Fig. 25-4). The perianal skin is gently stroked with a cotton-tipped swab to obtain the cutaneous anal reflex. Colloquially termed anal wink, circumferential contraction of the anal skin and underlying EAS is normally seen. This finding provides gross assessment of pudendal nerve integrity.
Photograph showing the “dovetail” sign, which is created by disruption of the anterior portion of external anal sphincter (EAS). Radial skin spikes are typically formed by attachment of skin to the EAS but are commonly absent from 10 to 2 o’clock (asterisks) in those with this disruption.
With digital rectal examination, one can assess anal resting tone, sample for gross or occult blood, and palpate masses or fecal impaction. In addition, squeeze pressure can subjectively be judged during voluntary patient contraction of the EAS around a gloved finger inserted into the anorectum. Last, during patient Valsalva maneuver, one observes for excessive perineal body descent, vaginal wall prolapse, rectal prolapse, or muscle incoordination (Fig. 25-5). With the latter, a paradoxic contraction—that is, abnormal sphincter contraction around the finger—may be elicited during patient Valsalva when an examining finger is inserted into the anorectum. Digital rectal examination is reasonably accurate relative to manometry for assessing anal resting tone and squeeze function and for identifying dyssynergia (Orkin, 2010; Tantiphlachiva, 2010).
During patient Valsalva, a full-thickness rectal prolapse protrudes through the anal opening.
Physical and historical findings typically guide the remainder of testing, which may include imaging and functional studies. Of these, anorectal manometry is performed mainly in academic institutions with an anophysiology laboratory prior to surgical intervention. It is a functional test that allows objective assessment of: (1) rectal compliance and rectal sensation, (2) reflexes, and (3) anal sphincter function (Table 25-5). During this test, a small flexible tube containing an inflatable balloon tip and pressure transducer is inserted into the rectum (Fig. 25-6). First, rectal compliance and sensation may be determined by sequentially inflating a rectal balloon to various volumes. Decreased rectal compliance may be noted by an inability to inflate a balloon to typical volumes without patient discomfort. This may indicate a rectal reservoir that is unable to appropriately store stool. In contrast, decreased perception of balloon insufflation may indicate neuropathy.
TABLE 25-5Functional Testing for Patients with Fecal Incontinencea ||Download (.pdf) TABLE 25-5 Functional Testing for Patients with Fecal Incontinencea
| ||Manometry || || || || |
|Factors ||Resting ||Squeeze ||RP ||RC ||DG ||EAUS ||MRI ||EMG |
|IAS ||+ || || || || ||+ ||+ || |
|EAS || ||+ || || || ||+ ||+ ||+ |
|Puborectalis || || || || ||+ || ||+ ||+ |
| Rectum |
|Perception || || ||+ || || || || || |
|Compliance || || || ||+ || || || || |
|Reservoir || || ||+ ||+ ||+ || || || |
|Megarectum || || ||+ || ||+ || ||+ || |
| Pelvic floor |
|Perineal descent || || || || ||+ || ||+ || |
|Anorectal angle || || || || ||+ || ||+ || |
| Neural |
|Pudendal nerve || ||+ || || || || || ||+ |
Manometry tube and balloon, empty (A) and after filling (B).
Second, sphincter reflexes are also assessed during pressure measurements. During balloon insufflation, relaxation of the IAS should accompany rectal distention via the rectoanal inhibitory reflex (p. 563).
Third, IAS resting pressure and EAS squeeze pressure are then measured at incremental points as the balloon is slowly withdrawn from the rectum. In general, decreased pressure readings may indicate structural disruption, myopathy, or neuropathy. As an additional test, the rectal balloon expulsion test may be performed as a patient simulates defecation and expels the balloon. The balloon expulsion test is mainly used in patients with constipation and attempts to differentiate between obstructed constipation and functional constipation (Minguez, 2004).
The main limitation with manometry is that normal values may be seen in incontinent patients and vice versa. Despite this disadvantage, anal manometry plays an important role in AI evaluation.
Also known as transanal sonography, this technique is now the primary diagnostic imaging technique to evaluate the integrity, thickness, and length of the IAS and EAS (Fig. 25-7). It is performed for many patients during FI testing, especially if sphincter integrity is in question. The technique uses a rotating endoprobe with a ≥10-MHz transducer, which provides a 360-degree evaluation of the anal canal. Sonography gel is placed on the probe tip, which is sheathed with a condom prior to insertion into the anus. This tool allows diagnosis of anterior anal sphincter defects in women with a known history of clinically diagnosed anal sphincter disruption and also in those with unrecognized or misdiagnosed defects at the time of delivery. Prior to the common use of endoanal sonography (EAUS), women with these “occult”—that is, solely sonographically diagnosed—anal sphincter defects were labeled as having “idiopathic” FI and were not considered good candidates for surgical correction.
Cross-sectional anal endosonography images at level of mid anal canal. A. A woman with normal anal sphincters. B. Anterior defects of the external and internal anal sphincter muscles. EAS = external anal sphincter; IAS = internal anal sphincter. Dashed lines and (arrows) in B illustrate the ends of the torn EAS.
In addition to the anal sphincters, this modality can image the puborectalis muscle and perineal body. Oberwalder and colleagues (2004) showed that in a group of incontinent women, perineal body thickness <10 mm was associated with anal sphincter defects in 97 percent of cases, whereas perineal body thicknesses of 10 to 12 mm were associated with sphincter defect in only one third of patients with FI. Perineal body thickness >12 mm was infrequently associated with these defects.
Newer techniques may also be informative. For example, dynamic endoanal or transperineal ultrasound can permit functional assessment of the anorectum, similar to defecography, described next (Vitton, 2011).
During this radiographic test, also known as defecography, the rectum is opacified with a thick barium paste, and the small bowel fills with a barium suspension given orally. Radiographic or fluoroscopic imaging is then obtained while a patient is resting, contracting her sphincter, coughing, and straining to expel the barium.
This test of dynamic rectal emptying and anorectal anatomy is not widely used to assess evacuation disorders unless obstructive causes for AI are suspected. Accordingly, it may be obtained if intussusception, internal rectal prolapse, enterocele, or failed relaxation of the puborectalis muscle during defecation is a concern.
Magnetic Resonance Imaging
Magnetic resonance (MR) imaging of the anal sphincter complex can be done either with an endoanal coil placed in the anorectum or with external phased-array coils. This latter external coil technique is preferred because physical anatomy is less distorted and the lack of an intraluminal coil increases patient comfort (Van Koughnett, 2013a). MR imaging is more expensive than EAUS, and its value for anal sphincter evaluation is controversial on several points. First, EAUS is more sensitive in detecting IAS abnormalities, whereas MR imaging is more sensitive in visualizing EAS morphology, including atrophy (Beets-Tan, 2001; Rociu, 1999). This may have value preoperatively, as patients with EAS atrophy may have poorer results following anal sphincteroplasty compared with those without atrophy (Briel, 1999). Second, MR imaging results vary considerably among interpreters and depend on their experience level. Thus, either EAUS or MR imaging can only be recommended in FI evaluation if sufficient experience is available (Terra, 2006).
Another MR imaging modality, termed dynamic MR imaging, allows dynamic examination of rectal emptying and evaluation of pelvic floor muscles during rest, squeeze, and defecation (Gearhart, 2004; Kaufman, 2001). Thus, it simultaneously permits a survey of pelvic anatomy, organ prolapse, and defecatory function. This may be particularly appealing to patients requiring multiple anorectal tests (Khatri, 2014; Van Koughnett, 2013a). However, it is technically difficult, more expensive, and again requires an experienced radiologist. Moreover, other than avoiding the ionizing radiation of evacuation proctography, this technique offers no advantage for studying rectal function. In addition, the variability of pelvic MR imaging measurements among readers is high (Lockhart, 2008). Despite these limitations, this test has been increasingly adopted in many academic settings, including our institution.
This test uses a needle or surface electrode to record electrical activity of muscles at rest and during contraction. During needle electromyography (EMG), needle electrodes are inserted through the skin into a muscle, and electrical activity detected by these electrodes is displayed graphically. In evaluation of AI, EMG may be used to assess the neuromuscular integrity of the EAS and puborectalis muscle. Specifically, by measuring action potentials from muscle motor units, EMG can help clarify which portions of these muscles are contracting and relaxing appropriately. Additionally, following injury, muscle may be partially or completely denervated, and compensatory reinnervation may then follow. Patterns characteristic of such denervation and reinnervation may be identified with EMG.
Unlike needle electrodes, surface patch electrodes are placed on the darker-skinned area of the anus, cause little discomfort to the patient, and carry no risk of infection. However, this technique is prone to artifacts. In comparing the two, needle EMG is painful but provides useful information regarding sphincter innervation. Surface EMG may be best used during repetitive biofeedback sessions. In general, its use is limited to research centers.
Pudendal Nerve Terminal Motor Latency Test
This stimulation test of the pudendal nerve measures the time delay between electrical nerve stimulation and EAS motor response. This delay, also termed latency, if prolonged, may indicate pudendal nerve pathology, which may be a cause of AI.
During pudendal nerve terminal motor latency (PNTML) testing, a stimulating electrode positioned on an examiner’s gloved fingertip is connected to a pulsed-stimulus generator. The pudendal nerves are transanally stimulated through the lateral walls of the rectum at the level of the ischial spines by this electrode. The action potential response of the EAS is received by recording electrodes at the base of the examining finger and registered on an oscilloscope.
Although PNTML prolongation has long been considered a marker of idiopathic FI, this test provides little information regarding FI etiology. PNTML results have been contradictory and this test is not endorsed by many experts, including the American Gastroenterological Association (Diamant, 1999). Moreover, the relationship of pudendal nerve function, typically assessed by PNTML, to sphincteroplasty outcome remains unclear (Madoff, 2004a). One study found no association between pudendal nerve status and long-term postoperative anal continence (Malouf, 2000). Accordingly, it has been replaced by more specific and sensitive tests for sphincter muscle innervation such as EMG (Barnett, 1999). Currently, needle electromyography is the only available technique for documenting neurogenic injury but is performed only in select academic centers and mostly in the context of research clinical trials.
Unfortunately, EMG and PNTML do not provide an assessment of all the peripheral nerves that innervate the anorectum. In addition, both tests are associated with patient discomfort. These significant limitations have prevented widespread acceptance or use of needle EMG and PNTML testing. Currently, anorectal neurologic injury is assessed by performing anal EMG or PNTML but only in specialized centers. Newer and less invasive approaches for documenting neurogenic injury have been described and are under investigation (Meyer, 2014; Rao, 2014).
Colonoscopy and Barium Enema
Based on the history and physical examination, these tests may be indicated to exclude inflammatory bowel conditions or malignancy.
Treatment of FI is highly individualized and dependent on etiology, severity, available treatment options, and patient health. Because FI etiology is often multifactorial, treatments that target only one mechanism (such as sphincter weakness) are unlikely to benefit all patients with FI. Moreover, because current surgical outcomes are less than optimal, most patients, even those with anatomic defects, are initially treated conservatively. Of conservative options, management may include patient education, normalization of stool consistency, behavioral techniques, and daily pelvic floor muscle strengthening exercises (Whitehead, 2015).
For patients with minor incontinence, the use of bulking agents can thicken stool consistency and create feces that are firmer and easier to control (Table 25-6). Common side effects such as abdominal distention and bloating can be improved by starting with smaller doses or switching to a different agent. In support of this practice, a small randomized trial showed that fiber supplementation decreased diarrhea-associated FI (Bliss, 2001). However, evidence that fiber supplements benefit patients with constipation-associated FI is lacking.
TABLE 25-6Medical Management of Fecal Incontinence ||Download (.pdf) TABLE 25-6 Medical Management of Fecal Incontinence
|Treatment ||Brand Name ||Oral Dosage |
| Bulking agents || || |
|Psyllium ||Metamucil ||1 tbsp. mixed into 8 oz. of water 1–3 times daily |
|Psyllium ||Konsyl ||1 tsp. mixed into 8 oz. of water 1–3 times daily |
|Methylcellulose ||Citrucel ||1 tbsp. mixed into 8 oz. of water 1–3 times daily |
| Loperamide hydrochloride ||Imodium ||2–4 mg, 1–4 times daily to a maximum daily dose of 16 mg |
| Diphenoxylate hydrochloride ||Lomotil ||5 mg, 1–4 times daily to a maximum daily dose of 20 mg |
| Amitriptyline ||Generic ||10–25 mg at bedtime; increase by 10–25 mg weekly up to 75–150 mg at bedtime or a therapeutic drug level |
Also to bulk stool, agents that slow fecal intestinal transit time can reduce overall stool volume by increasing the time available for the colon to reabsorb fluid from stool. One such agent, loperamide hydrochloride (Imodium), also increases anal resting tone and thus may even benefit patients with FI and no diarrhea (Read, 1982). Side effects are uncommon and include dry mouth. One ongoing trial is comparing loperamide and oral placebo for FI treatment (National Institute of Child Health and Human Development, 2014).
Diphenoxylate hydrochloride (Lomotil) is used in the same capacity as loperamide, and dosing is similar. Although diphenoxylate is a Schedule V substance, potential for physical dependence is minimal. Of other possible medications, amitriptyline is a tricyclic antidepressant that can be used to treat idiopathic FI. Although the mechanism of action is poorly understood, some of its beneficial effects may be related to its anticholinergic properties. Other agents such as cholestyramine and clonidine, an α-adrenergic agonist, have been studied, but current data are limited (Whitehead, 2015). The laxative lactulose aids some nursing home residents with FI associated with fecal impaction (Omar, 2013).
To guide drug selection, one systematic review analyzed pharmacologic agent use for FI treatment in adults (Omar, 2013). These reviewers noted that antidiarrheal drugs improve diarrhea-associated FI more than placebo, and loperamide is more effective than diphenoxylate. However, overall, they commented on the poor quality of evidence.
Daily, timed, tap-water enemas or glycerin or bisacodyl suppositories (Dulcolax) may be used to empty the rectum after eating. These provide acceptable and helpful options for some patients with constipation symptoms associated with AI. These may include women with normal stool consistency but difficulty evacuating due to anatomic reasons such as rectocele with stool trapping or those with denervation and impaired rectal sensation. All these may lead to accumulation of a large mass of solid stool in the rectum and leaking of loose stool around it. Bulking agents can be used concurrently with these evacuation methods to diminish stooling between desired defecations.
Biofeedback and Pelvic Floor Therapy
Biofeedback is usually selected to increase neuromuscular conditioning. Specifically, for FI, therapy goals aim to improve anal sphincter strength, sensory awareness of stool presence, and coordination between the rectum and the anal sphincter (Rao, 1998). Treatment protocols are individualized and dictated by the underlying dysfunction. Accordingly, the number and frequency of sessions required for improvement varies, but commonly three to six 1-hour, weekly or biweekly appointments are needed. In many cases, reinforcing sessions at various subsequent intervals are also recommended.
Biofeedback has been noted to be an effective treatment for FI, and up to 80 percent of treated patients show symptom improvement (Engel, 1974; Jensen, 1997; Norton, 2001). Despite this, one Cochrane review found insufficient evidence of biofeedback’s benefits for FI (Norton, 2012). However, a randomized controlled trial by Heymen and coworkers (2009) offers support. These investigators initially provided education materials and instruction regarding fiber supplements and/or antidiarrheal medication. Patients who were adequately treated by these strategies (21 percent) were excluded from further study. The remaining 107 patients, who remained incontinent and dissatisfied, then progressed to treatment, either biofeedback or pelvic floor exercises. Biofeedback training more effectively reduced FI severity and number of days with FI. Moreover, 3 months after training, 76 percent of biofeedback patients reported adequate relief of FI symptoms compared with only 41 percent of patients treated with pelvic floor exercises. Twelve months later, biofeedback improvement persisted.
The results of this and other trials suggest that biofeedback may not be necessary for patients with milder FI symptoms. However, for those with more severe FI symptoms, instrument-assisted biofeedback is effective (Whitehead, 2015).
Pelvic Floor Muscle Strengthening
Also known as Kegel exercises, active pelvic floor muscle training (PFMT) exercises voluntary contract the levator ani muscles. Performance of these exercises is fully described in Chapter 23. As noted, these alone are less effective than biofeedback for patients with more severe FI symptoms (Heymen, 2009). However, exercises are safe and inexpensive and may benefit patients with mild symptoms, especially if performed in conjunction with other interventions, such as patient education, diet modification, and medical management.
In contrast to active PFMT, anal musculature can be passively stimulated electrically by electrodes. However, when used as sole therapy, electrical stimulation of the anus appears to be ineffective (Whitehead, 2015).
Currently available FI surgical procedures are often associated with less than optimal results and with postoperative morbidity. Accordingly, surgery is reserved for those patients with major structural abnormalities of the anal sphincter(s), those with severe symptoms, and those who fail to respond to conservative management.
This is the most commonly performed FI corrective operation. Repair of the EAS and/or IAS is indicated for women with acquired AI and an anterior sphincter defect following an obstetric or iatrogenic injury. Two methods may be used for sphincter repair and include an end-to-end technique and an overlapping method, both described in Section 45-25. The end-to-end technique is most frequently used by obstetricians to reapproximate torn ends of an anal sphincter at delivery. However, in patients remote from delivery with a sphincter defect and FI, the overlapping technique is preferred by most colorectal surgeons and urogynecologists.
With the overlapping method performed remote from delivery, short-term continence improvements of 67 percent were previously reported (Madoff, 2004a). However, recent reports show significant deterioration of continence during long-term postoperative surveillance (Bravo Gutierrez, 2004; Glasgow, 2012). In a single, retrospective study, no patients remained completely continent to liquid and solid stool at 10 years (Zutshi, 2009). Hypotheses regarding this deterioration include aging, scarring, and progressive pudendal neuropathy related either to initial injury or to repair. Patients who fail to improve after anal sphincteroplasty and who are found to have a persistent sphincter defect may be candidates for a second sphincteroplasty. However, those with an intact sphincter following repair and persistent symptoms are only considered candidates for conservative management or one of the salvage or minimally invasive surgical procedures described later.
Currently, no conclusive evidence supports that the overlapping method, if used at delivery, leads to results superior to those obtained with the traditional end-to-end method of anal sphincter repair (Farrell, 2012; Fitzpatrick, 2000; Garcia, 2005). Moreover, overlapping repair requires increased technical skills and carries the potential for increased blood loss, operating time, and pudendal neuropathy. For these reasons, the end-to-end technique is likely to remain the standard method for sphincter reapproximation at delivery until further data from randomized trials are available. Importantly, primary prevention of these lacerations should continue to be emphasized.
Diversion (Colostomy or Ileostomy)
Diversion is reserved for patients with incapacitating FI who have failed other treatments (Sections 46-17 and 46-19). For these selected patients, such procedures can significantly improve their quality of life.
Of these, gracilis muscle transposition is advocated for patients who have failed sphincter repair or those with a sphincter defect too large to allow muscle reapproximation (Baeten, 1991). Dynamic graciloplasty separates the gracilis tendon from its point of insertion at the knee, wraps the muscle around the anus, and attaches the tendon to the contralateral ischial tuberosity. To squeeze the anus closed, the gracilis muscle is then stimulated with an electrical pulse generator that is implanted in the abdominal wall. This procedure is not currently performed in the United States, as the pulse generator is not approved by the Food and Drug Administration (FDA) (Cera, 2005).
Implanting an artificial anal sphincter is another option to mimic sphincter function, but again, it is infrequently performed in the United States. With this, a fluid-inflated cuff is implanted around the anus, a reservoir balloon is placed within the abdominal wall, and a control pump is inserted into one labium majus. When fully inflated, the cuff occludes the anal canal. When defecation is desired, the control pump in the labia is squeezed to move fluid from the anal cuff into the reservoir balloon. The cuff, when fluid-empty, relaxes pressure around the anus and permits defecation. The fluid within the reservoir then returns to the anal cuff to restore circumferential pressure and continence (Christiansen, 1987).
A third procedure, postanal pelvic floor repair, has largely been abandoned. The procedure is designed to reestablish the anorectal angle and to lengthen and tighten the anal canal. Through an intersphincteric approach, sutures are placed between the ends of the iliococcygeus, pubococcygeus, puborectalis, and external anal sphincter muscles. Although originally reported to improved incontinence in up to 80 percent of patients, similar results have not been replicated (Browning, 1983; Deen, 1993; Parks, 1975).
Minimally Invasive Procedures
In 2011, the FDA approved sacral nerve stimulation (SNS) for FI treatment. Also known as sacral neuromodulation, this surgery is typically offered to women who have failed to adequately improve with multiple other conservative therapies, and a full description of the InterStim System procedure appears in Section 45-12. To summarize, an electrode is placed near the S3 nerve root and connected to a temporary pulse generator. Electrical charges to this nerve root may modulate abnormal afferent impulses, although the exact mechanism of SNS action for FI remains unknown (Gourcerol, 2011). Patients who show ≥50 percent improvement during the temporary test phase are eligible for a permanent pulse generator.
In one prospective trial, 90 percent of 133 patients proceeded from temporary to permanent stimulation (Wexner, 2010). For this study, therapeutic success was defined as a 50-percent or greater reduction of incontinent episodes per week compared with baseline. At 12 months, 83 percent of subjects achieved therapeutic success, and 41 percent achieved 100 percent fecal continence. At 24 months, therapeutic success was found in 85 percent. At 5 years, 89 percent were deemed a therapeutic success, and 36 percent reported complete continence (Hull, 2013). Limited data are available from patients with an underlying EAS defect, but these suggest that SNS is also effective for this group (Chan, 2008; Matzel, 2011).
Percutaneous Tibial Nerve Stimulation
The posterior tibial nerve contains fibers from the sacral nerves. Stimulation of its peripheral fibers transmits impulses to the sacral nerves and reflexively neuromodulates the rectum and anal sphincters (Shafik, 2003). Percutaneous tibial nerve stimulation (PTNS) is carried out with a needle inserted through the ankle skin in a position posterior and superior to the medial malleolus. This needle is then coupled with an electronic pulse generator. Outpatient stimulation sessions usually last 30 minutes and are provided one to three times weekly. Suitable candidates have criteria similar to those for SNS.
One review of 13 studies showed that 62 to 82 percent of patients reported at least a 50-percent reduction in the frequency of FI episodes (Thomas, 2013). Compared with the InterStim System, PTNS requires repetitive treatments to maintain effectiveness. However, PTNS is a minimally invasive outpatient technique with almost no associated morbidity (Thin, 2013). A randomized controlled trial comparing SNS and PTNS in the treatment for FI is currently in progress (Marti, 2015).
Injecting inert substances around the anal canal in patients with FI aims to increase resting anal canal pressure (Shafik, 1993). Although many patients with FI may be candidates for injectables, the ideal candidate is one who has seepage or mild to moderate FI, who has failed medical management, but who is not yet ready to undergo surgery (Van Koughnett, 2013b).
The results of a large multicenter randomized controlled trial support the efficacy of dextranomer injections compared with sham injections (Graf, 2011). At 3 months, 52 percent of the dextranomer-injected patients had at least a 50-percent decline in FI frequency, whereas only 31 percent of sham-treated patients achieved this reduction. A surveillance study showed that benefits persisted for 36 months (Mellgren, 2014).
This outpatient procedure is currently used in the United States to treat FI in patients with no evidence of sphincter defects or pudendal neuropathy. It delivers temperature-controlled radiofrequency energy to the IAS by means of a specifically designed anoscope. Resulting tissue heating is believed to cause collagen contraction followed by focal wound healing, remodeling, and tightening. Studies to date have involved only small cohorts. Efron and colleagues (2003) showed a median 70-percent resolution of symptoms in 50 patients. However, one retrospective series showed long-term benefit in only 22 percent, and most patients underwent additional treatments (Abbas, 2012).
Several other treatment options are currently under investigation. First, a mesh sling can be inserted surgically through small incisions lateral to the anus. By a transobturator approach, the mesh is then tunneled beneath the puborectalis muscle to add support. A trial evaluating this technique has been completed, but long-term results are not yet available.
Second, a vaginally placed bowel-control device offers a nonsurgical option. The vaginal insert contains a silicone-coated stainless steel base and posteriorly directed balloon. Using a pump, the vaginal insert is inflated to collaterally occlude the rectum. Thus, its primary limitation mirrors that for vaginal pessaries, namely, that not all women are successfully fitted. In one study, this device significantly improved objective and subjective measures of FI (Richter, 2015). Approximately 86 percent of patients considered bowel symptoms “very much better” or “much better.” Moreover, no serious adverse events were reported. However, longer-term outcome data are needed.
Anal plugs present another therapy option, but most current devices are uncomfortable and poorly tolerated. However, newer models made of softer material are under investigation (Meyer, 2014).
Last, magnetic beads strung on an elastic band can be inserted surgically around the anal canal to increase the resting pressure. Small studies have shown continence results comparable to the artificial anal sphincter and to SNS but with fewer complications (Whitehead, 2015). However, this device is not yet approved in the United States.