Sacral agenesis

Fecal incontinence is defined as the loss of voluntary control to retain stool in the rectum.[1] While this problem can occur in persons of any age, it is most common in the elderly, especially those who are institutionalized. A study in the general British population[2] found that when fecal incontinence was defined as the "involuntary leakage of feces in inappropriate places or inappropriate times twice or more per month," its prevalence was 0.42 percent in adults under the age of 65 years. In adults over 65 years of age, fecal incontinence was present in 1.1 percent of men and 1.3 percent of women.[2]

In the United States, the prevalence of fecal incontinence, defined as a one-month or longer history of frequent leaking or passage of stool at unwanted times, has been reported to be 7.8 percent.[3] Fecal soiling was present in 7.1 percent of the surveyed population, while gross incontinence occurred in 0.7 percent of those surveyed.[3] A study conducted in Wisconsin[4] found the incidence of involuntary loss of both stool and flatus to be 2.2 percent.

Independent risk factors for fecal incontinence include female sex, advancing age, poor general health and physical limitations.[4] Double incontinence (urinary and fecal) in the elderly is 12 times as likely as fecal incontinence alone.

Despite these substantial numbers, fecal incontinence is probably underreported, because affected persons feel ashamed or guilty about the problem or because they have previously had traumatic medical experiences.[5,6] In many cases, medical treatment is sought only when the frequency of soiling has increased.[7]

Fecal incontinence also affects family members and spouses who serve as caregivers to affected persons. While the cost of caring for patients with fecal incontinence is unknown, a highly conservative estimate of the direct costs of caring for persons of all ages who have urinary incontinence is $7 billion annually in the United States.[8]

Pathophysiology

Fecal continence is maintained by the following factors: rectal sensation; rectal compliance and accommodation; timely contraction of the puborectalis muscle and the internal and external anal sphincters (anal sphincter mechanism), and a person's mobility and motivation to maintain continence. Abnormalities of any of these factors, alone or in combination, can lead to incontinence. Even if these factors are normal, an excess volume of liquid stool and rapid colonic transit can lead to fecal incontinence.[9]

RECTAL SENSATION

Normal sensation of stool in the rectum is necessary for continence. Decreased sensation of stool in the rectum may be present in patients with spinal disease, dementia, stroke, encephalopathy, fecal impaction, spine bifida, idiopathic fecal incontinence and diabetes complicated by neuropathy. Since patients with decreased rectal sensation are not consciously aware of stool entering the rectum, relaxation of the internal anal sphincter by distention of the rectum without the appropriate conscious contraction of the external anal sphincter may result in incontinence.

RECTAL COMPLIANCE

The rectum is normally a highly compliant reservoir in which intraluminal pressures remain low despite large volumes. However, in diseases in which rectal compliance may be diminished, such as radiation proctitis[10] and ulcerative colitis,[11] even small volumes in the rectum result in high intraluminal pressures, which may lead to severe urgency and incontinence.

ANAL SPHINCTER MECHANISM

The anal sphincter mechanism is composed of the internal anal sphincter, the external anal sphincter and the puborectalis muscles. The internal anal sphincter is under autonomic (thus, involuntary) control, while the external anal sphincter and the puborectalis muscles are skeletal (striated) muscles that are under voluntary control. Approximately 50 to 85 percent of the resting sphincter pressure is from the internal anal sphincter.

The external anal sphincter is innervated by the pudendal nerves, while the puborectalis muscles are supplied by the pelvic branches of the third and fourth sacral nerves. Spinal reflexes maintain continence by transient contraction of the external anal sphincter during brief periods in which continence is challenged, such as during coughing.

Relaxation of the internal anal sphincter during rectal distention is important in enabling rectal contents to come into contact with the upper anal canal, where sensory fibers differentiate between flatus and stool. This relaxation of the internal anal sphincter in response to rectal distention is known as the rectoanal inhibitory reflex. Thus, impairment of the external anal sphincter from damage to the pudendal nerve (e.g., during childbirth) may be associated with incontinence.[12]

MOBILITY

Impaired mobility can be a precursor to fecal incontinence in that physical limitations, such as being confined to a bed or a wheelchair or using a walker or a cane, may make it impossible for patients to make it to the bathroom in time to prevent incontinence. As devastating as fecal incontinence can be, the fear associated with this problem, similar to the fear of falling, can result in limitation of daily activity. The decreased activity level can predispose patients to physical and psychologic conditions that further reduce physical exercise and social interaction. Therefore, it is important to understand how interventions directed at older patients can postpone disabilities associated with age-related illnesses or conditions and how these interventions can compensate for the functional deficits that often occur in later life.[13]

PSYCHOSOCIAL COMPLICATIONS

In many cases, fecal incontinence results in progressive social isolation, as patients attempt to avoid embarrassing accidents and loss of individual potential. Thus, a patient's day may revolve around making it to the bathroom. Fecal incontinence is also associated with depression, a sense of inadequacy, low self-esteem and sexual dysfunction. Once bowel control is lost, a vicious circle can develop, where social isolation leads to worsening depression which, in turn, leads to further isolation.

Etiology

Some causes of fecal incontinence are listed in Table 1. Fecal incontinence can be caused by multiple and often interacting conditions. Although there is a trend toward weakening of the sphincter muscles in elderly patients, fecal incontinence should not be regarded as an inevitable consequence of aging. In most cases, the etiology can be determined by a systematic evaluation.

Similarly, diarrhea resulting from any number of causes may lead to fecal incontinence in elderly patients, especially those with limited mobility. Longstanding diabetes mellitus may also cause an autonomic neuropathy, with decreased tone of the internal anal sphincter and subsequent fecal incontinence.[15]

Assessment of Fecal Incontinence

CLINICAL EVALUATION

The first step in the management of fecal incontinence is acknowledgment of the problem. Since patients do not often mention incontinence as a chief complaint, a careful clinical history should be obtained.

Once fecal incontinence is identified, its severity should be assessed. Minor incontinence consists of loss of flatus control or occasional liquid stool soiling, while major incontinence is the involuntary loss of significant amounts of liquid or solid stool. The need for perianal pads or diapers may indicate the severity of the incontinence.

With the identification of fecal incontinence, the history should then focus on predisposing factors. In women with children, a careful obstetric history should be elicited, especially the number of vaginal deliveries, the duration of labor, the use of obstetric forceps and the occurrence of perineal lacerations (i.e., episiotomies). In both men and women, excessive straining with defecation, rectal fullness, a sensation of incomplete evacuation and a mass protruding from the rectum may all be signs of rectal prolapse. New-onset weakness, difficulty walking, lower back pain and concomitant difficulties with micturition may be signs of neurologic disease. A detailed past medical history, as well as a complete review of medications, should be obtained.

A physical examination, including a complete anorectal examination, should be performed in all patients with fecal incontinence. The perianal area should be inspected for fistulae, which has symptoms that may be mistaken for minor incontinence. All women should be checked for episiotomy scars and evidence of thinning of the perineum. An assessment for peripheral neuropathy should be performed, especially in patients with diabetes mellitus. The cutaneous anal reflex ("anal wink") elicited by lightly stroking the perianal skin is often diminished in patients with pelvic neuropathy.

The tone and strength of the external anal sphincter should be assessed during the digital examination by having the patient squeeze. The puborectalis muscle, which is palpable as a semicircular ring posteriorly in the rectum just proximal to the anal canal, should move anteriorly during the squeeze command and posteriorly during the command to bear down (Valsalva maneuver).

Additional tests are required in elderly patients with the recent onset of fecal impaction or diarrhea not associated with another illness or a change in medications (especially narcotics, calcium channel blockers, tricyclic antidepressants and antihistamines [histamine [H.sub.1] blockers]). Flexible sigmoidoscopy should be performed; when clinically indicated, a barium enema, colonoscopy and small bowel studies may also be necessary. Levels of thyroid-stimulating hormone, calcium, electrolytes and blood urea nitrogen should also be checked, because abnormalities may result in altered bowel habits.

PHYSIOLOGIC TESTING

Since the etiology of fecal incontinence is often multifactorial, especially in elderly patients, a combination of tests is usually needed to properly determine the causes and to direct treatment. The most frequently used physiologic tests are anorectal manometry, cinedefecography and electromyography. Whether some or all of these tests are necessary is controversial. Often, the need for further evaluation is determined by the history and the physical examination.

Anorectal Manometry. This test is performed to determine the resting and squeeze pressure of the sphincter muscles, as well as to measure the anal canal length. An automated pull-through of the manometry catheter can provide a three dimensional view of the anal canal pressure zones to determine if a segmental defect, such as a tear in the sphincter, is present. Intrarectal balloon distention is helpful-for determining rectal sensation and compliance. Reflex responses of the internal and external anal sphincters can be stimulated by rectal balloon distention and are useful for quantifying internal and external anal sphincter function.[16]

Electromyography. This modality is used to measure the electrical potential of the muscle fibers within the anal sphincters. Thus, it determines the neuromuscular integrity of the sphincter muscles, which is especially important after surgery or traumatic injury. Either concentric-needle and single-needle electromyography may be used. Pudendal nerve latency measurements are also helpful for determining the integrity of the nerve.

Cinedefecography. For this radiologic evaluation of the defecation mechanism, a barium paste is instilled in the rectum, and the patient is asked to squeeze and then evacuate the material while under fluoroscopic surveillance. During normal defecation, the puborectalis muscle relaxes, straightening the rectum, and the pelvic floor descends. During the squeeze, the puborectalis muscle contracts and the pelvic floor rises. Defecography can also detect intussusception (early prolapse), rectoceles and enteroceles.

Other Tests. While anal ultrasound and mucosal electrosensitivity testing may be useful, they are not widely available.

Treatment

CONSERVATIVE MANAGEMENT

The management of fecal incontinence depends on its etiology. Fecal impaction requires not only relief of impaction, but also preventive measures to reduce the risk of further episodes. While enemas usually relieve impaction, manual release of the feces is often required. If possible, regular bowel habits should be restored. Adequate hydration and exercise are also essential. The usefulness of dietary fiber is controversial, but this approach may be tried. Suppositories or enemas may be required on a regular basis. Stool softeners and laxatives should be avoided if possible, since diarrhea can also result in incontinence in many of these patients.

In patients with loose stools or an increased stool volume, antidiarrheal agents may be tried. Many elderly patients with minimal incontinence may be managed by changing the consistency or volume of the stool. When antidiarrheal agents are to be used, loperamide (Imodium) is the drug of choice, because it slows intestinal motility and at high doses also results in increased anal pressures. Since overuse of an antidiarrheal agent can cause constipation and fecal impaction with subsequent fecal incontinence, judicious dosing is necessary.

In patients with recurrent fecal impaction, regular use of enemas may also be helpful in keeping the rectum empty. Because gastric distention causes an increase in colonic motility (gastrocolic reflex), scheduled bowel movements, especially after meals, may be beneficial. Proper positioning of the patient on the toilet, with feet slightly elevated to prevent excessive straining, may also be helpful.

ANORECTAL BIOFEEDBACK

The biofeedback treatment of fecal incontinence, first described in 1974,[17] uses rectal balloon distention to help patients coordinate contraction of the external anal sphincter. Patients are usually given visual cues and encouragement during appropriate contractions of the sphincter. Since this treatment is based on a learning process, change is gradual. Reduction of incontinence becomes evident as muscle control and other continence skills are practiced and applied.

Biofeedback is successful in approximately two-thirds of patients who retain some degree of rectal sensation and functioning of the external anal sphincter. However, multiple sessions are often necessary, and patients need to be highly motivated. Electronic home biofeedback systems are available and may be helpful as adjuvant therapy.

SURGICAL TREATMENT

Several surgical approaches to fecal incontinence have been tried, with varying success, when conservative management has failed. These treatments include sphincter repair, implantation of the gracilis or gluteus muscles, and colostomy. The approach that is used depends on the cause of the incontinence and the expertise of the surgeon.

Acute injuries to the sphincter muscles usually occur after obstetric trauma (anterior sphincter injury) or fistula repair (posterior sphincter injury). These injuries are often managed by direct repair using one or more of the following operations: apposition, overlapping and plication (or reefing) of the external anal sphincter.

When the external anal sphincter cannot be repaired (i.e., trauma or disuse), surgical reconstruction of an artificial sphincter may improve continence. Gracilis muscle, which is the most superficial muscle in the medial aspect of the thigh, has been used as a substitute anal sphincter since 1952.[10] The implantation of electrodes to stimulate the transposed muscle improves the success of this procedure. Following this procedure, 73 percent of patients remain continent for more than two years, and their quality of life is improved.[19]

REFERENCES

[1.] Schuster MM, Wehmueller J, eds. Keeping control: understanding and overcoming fecal incontinence. Baltimore: John Hopkins University Press, 1994. [2.] Thomas TM, Egan M, Walgrove A, Meade TW. The prevalence of fecal and double incontinence. Community Med 1984;6:216-20. [3.] Drossman DA, Li Z, Andruzzi E, Temple RD, Talley NJ, Thompson WG, et al. U.S. householder survey of functional gastrointestinal disorders. Prevalence, sociodemography, and health impact. Dig Dis Sci 1993;38:1569-80. [4.] Nelson R, Norton N, Cautley E, Furner S. Community-based prevalence of anal incontinence. JAMA 1995;274:559-61. [5.] Johanson JF, Lafferty J. Epidemiology of fecal incontinence: the silent aff iction. Am J Gastroenterol 1996;91:33-6. [6.] Sultan AH, Kamm MA, Hudson CN, Thomas JM, Bartram CI. Anal-sphincter disruption during vaginal delivery N Engl J Med 1993;329:1905-11. [7.] Loening-Baucke V. Efficacy of biofeedback training in improving fecal incontinence and anorectal physiologic function. Gut 1990;31:1395-402. [8.] Hu TW. Impact of urinary incontinence on healthcare costs. J Am Geriatr Soc 1990;38:292-5. [9.] Read NW, Harford WV, Schmulen AC, Read MG, Santa Ana C, Fordtran JS. A clinical study of patients with fecal incontinence and diarrhea. Gastroenterology 1979;76:747-56. [10.] Varma JS, Smith AN, Busuttil A. Correlation of clinical and manometric abnormalities of rectal function following chronic radiation injury. Br J Surg 1985;72:875-8. [11.] Denis P, Colin R, Galmiche JP, Geffroy Y, Hecketsweiler P, Lefrancois R, et al. Elastic properties of the rectal wall in normal adults and in patients with ulcerative colitis. Gastroenterology 1979; 77:45-8. [12.] Snooks SJ, Setchell M, Swash M, Henry MM. Injury to innervation of pelvic floor sphincter musculature in childbirth. Lancet 1984;2(8402):546-50. [13.] Levi L. Intervening in social systems to promote health. In: Ory MG, Abeles RP, Lipman PD, eds. Aging, health, and behavior. Newbury Park: Sage, 1992:276-95. [14.] Madoff RD, Williams JG, Caushaj PF. Fecal incontinence. N Engl J Med 1992;326:1002-7. [15.] Schiller LR, Santa Ana CA, Schmulen AC, Hendler RS, Harford WV, Fordiran JS. Pathogenesis of fecal incontinence in diabetes mellitus: evidence for internal-anal-sphincter dysfunction. N Engl J Med 1982;307:1666-71. [16.] Parks TG. The usefulness of tests in anorectal disease. World J Surg 1992;16:804-10. [17.] Engle BT, Nikoomanesh P, Schuster MM. Operant conditioning of rectosphincteric responses in the treatment of fecal incontinence. N Engl J Med 1974; 290:646-9. [18.] Pickrell KL, Broadbent TR, Masters FW, Metzger JT. Construction of a rectal sphincter and restoration of anal continence by transplanting gracilis muscle: report of four cases in children. Ann Surg 1952; 135:853-62. [19.] Baeten CG, Geerdes BP, Adang EM, Heineman E, Konsten J, Engel GL, et al. Anal dynamic graciloplasty in the treatment of intractable fecal incontinence. N Engl J Med 1995;332:1600-5.

The Authors TINA HIRSH, R.N. is clinical and research coordinator in the Division of Digestive Diseases at the University of California Los Angeles (UCLA) Functional Bowel and Motility Disorders Clinic. Ms. Hirsh completed her nursing training at Vanier College, Montreal, Quebec, and is currently working toward a Master of Public Health degree at the UCLA School of Public Health.

TONY LEMBO, M.D. is clinical instructor of medicine at the UCLA School of Medicine and associate director of the UCLA Functional Bowel and Motility Disorders Clinic. Dr. Lembo received his medical degree from Tufts Medical School, Boston, and completed postgraduate training in internal medicine and gastroenterology at the UCLA Medical Center.

Address correspondence to Tony Lembo, M.D., CURE, Building 115, Room 223, West Los Angeles Veterans Affairs Medical Center, 11301 Wilshire Blvd., Los Angeles, CA 90073.

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