Fecal Incontinence

Loss of voluntary control of defecation.

Fecal incontinence is a humiliating regression in bodily function that often causes anxiety, fear, embarrassment, and reclusiveness and can severely impair an elderly person's activity and socialization.

One study suggests that about 5% of the general population are affected. Fecal incontinence more frequently occurs in persons > 65 and is a primary reason for institutionalization of these patients; about 50% of institutionalized patients have fecal incontinence.

Etiology and Pathophysiology

Continence requires rectal and anal sensation to detect rectal filling and to discriminate among fluid, feces, and flatus. The reservoir capacity of the rectum and distal colon permits storing feces for variable periods of time. The coordination of internal and external anal sphincters is critical to blocking unintended defecation. The pelvic floor muscles, especially the puborectal muscle, preserve continence by retarding stool passage. Motivation is also essential to maintaining continence.

With age, contractile strength of the puborectal muscle, rectal elasticity, and external and internal anal sphincter pressures may decrease. Smaller distention volumes can lead to rectal urgency and inhibit anal sphincter tone. Causes of fecal incontinence in the elderly are listed in Table 110-6.

Fecal incontinence can result from fecal impaction, usually the result of impaired rectal sensation with flow of liquid stool around the fecal mass. These patients do not appropriately contract the striated muscle of the anal sphincter to prevent incontinence. Anal sphincter pressures usually become normal after disimpaction. In patients with global dementia, fecal incontinence may occur after meals or other activities that stimulate the gastrocolonic response, because these patients simply do not suppress the urge to defecate.

In ambulatory, noninstitutionalized elderly patients, fecal incontinence often occurs as a result of decreased contractile strength or impaired automaticity of the puborectal and external anal sphincter muscles. These changes are probably caused by age-related muscle weakness or partial denervation injury from pudendal neuropathy. The cause of pudendal neuropathy is unknown but may include repetitive stretching of the pudendal nerves in elderly women because of chronic constipation and defecatory straining, weaker pelvic floor muscles, and possibly spondylitic compression of nerve roots.

Diagnosis

The history and physical examination give clues to the severity of the problem and determine the integrity of the neuromusculature involved in maintaining continence. Several tests offer objective information useful in defining defects responsible for incontinence.

Anal manometry directly measures the pressure in the anal canal under basal conditions and with squeezing. In general, patients with fecal incontinence have significantly lower basal and squeeze pressures than age- and sex-matched controls, but many have normal sphincter pressures. Anal manometry is most valuable when it demonstrates abnormally low pressures and confirms a sphincter defect.

Manometric testing, which uses an inflatable balloon attached to a manometric catheter, tests rectal sensation, rectal compliance, and anorectal inhibitory reflex. Findings reflect the integrity of the neural pathways mediating sensation (both to consciousness and as a trigger for the anorectal relaxation reflex) and the motor responses.

Electromyography of the puborectal muscle and external anal sphincter assesses motor nerve supply and skeletal muscle responses, but its clinical usefulness is limited because of the discomfort experienced during the test.

Defecography assesses rectal capacity and diameter, anorectal angle (puborectal muscle function), and perineal descent (pelvic floor function). It can readily detect weakness of the puborectal muscle and pelvic floor.

Sigmoidoscopy can assess the mucosa and detect intraluminal lesions (eg, inflammation, melanosis coli due to laxative overuse, tumors, strictures) that may contribute to the symptoms.

Anal ultrasound assesses internal and external anal sphincter integrity by measuring muscle thickness and determining the presence or absence of sphincter disruption.

Treatment

Fecal incontinence can be treated in most patients. Treatment can reduce or eliminate episodes in > 50% of institutionalized patients.

Fecal impaction must be adequately treated. After the colon has been cleared, an immobilized or functionally impaired patient should be placed on a restricted fiber diet and have prophylactic enemas once or twice weekly to prevent recurrent impaction.

In nonconstipated patients without impaction, intervention can include drug therapy, biofeedback, and surgery.

The only drugs that have been evaluated for their effect on fecal incontinence are the opioid antidiarrheals, loperamide, and the combination of diphenoxylate and atropine. In patients with chronic diarrhea, loperamide 4 mg po tid significantly reduces the frequency of incontinent episodes and urgency and slightly increases basal anal sphincter pressure.

When fecal incontinence is associated with impaired reservoir capacity or with neurogenic abnormalities affecting colorectal function, a program of planned regular defecation and fiber restriction to reduce stool volume often reduces incontinence. If incontinence persists, loperamide (maximum 16 mg/day in divided doses) is titrated to decrease stool frequency or eliminate defecation.

Biofeedback is often effective for fecal incontinence due to rectosphincteric abnormalities. A balloon manometry device helps the patient obtain a conscious threshold for sensation of rectal distention and coordinate external anal sphincter contraction with rectal distention. An anorectal manometer attached to a visual display allows the patient to observe when sphincteric responses are appropriate; the patient subsequently attempts to reproduce the appropriate response. Although some elderly patients have difficulty with this approach because of anxiety and cognitive deficit, this technique has been successful in up to 70% of patients who are motivated, able to understand directions, and have some degree of rectal sensation.

Surgical intervention should be considered in patients who fail to respond to drug therapy and who have a disrupted anal sphincter. Although many surgical procedures have been used, the best procedure has not been determined.

When fecal incontinence is the result of rectal prolapse, resuspension or proctopexy can prevent further prolapse and can be combined with rectosigmoidectomy to restore continence in up to two thirds of patients. However, when prolapse is severe or prolonged, permanent neuropathic sphincter impairment may preclude a good surgical result.

For patients without full-thickness rectal prolapse, surgery should be considered only if conservative treatment has been unsatisfactory, because the available procedures are not easy to perform and may result in complications. The surgical approach should be individualized to suit the specific abnormalities.