Fecal Incontinence

Introduction and Incidence

Fecal incontinence may be defined as the inability to voluntarily control the release of flatus or stool until a socially convenient time and place. Fecal continence, which is learned in childhood, is one of the most important social milestones in development, and its loss is a devastating handicap. The prevalence of incontinence varies by gender, age, and definition; however, as many as 2% of women regularly experience difficulty controlling stool and at least 10% have difficulty controlling flatus. Incontinence is more common in parous women because childbirth is the most common cause of pelvic floor injury. Menopause also contributes through diminished trophic effects of estrogen on pelvic connective tissues, and symptoms frequently become manifest in the sixth or seventh decade. The overall cost of fecal incontinence to society is unknown, but the magnitude of the problem is illustrated by the fact that fecal incontinence is the second leading reason for admission of elderly persons to nursing homes—a reason more common than dementia. The hidden cost is a reduction in quality of life and lost opportunities resulting from this most embarrassing of symptoms.

Causes

Fecal continence depends on the presence of an intact anal sphincter mechanism, coupled with adequate rectal compliance and a normal volume and consistency of stool. A wide variety of anatomic and physiologic factors can alter continence, particularly changes in colonic transit and stool consistency, abnormal rectal physiology, abnormal anorectal sensation, pelvic floor denervation, and disruption of the integrity and function of the internal and external anal sphincters. In general, the four main causes are (1) abnormal stool volume and consistency; (2) neurologic disorders leading to sphincter weakness; (3) anatomic defects in the anal sphincters; and (4) abnormal rectal physiology. Because these problems often overlap, each area must be addressed to ensure accurate diagnosis and effective treatment.

Assessment

Many scoring systems have been proposed to categorize the severity of fecal incontinence. The use of such systems is important for accurate patient assessment, medicolegal documentation, and objective evaluation of treatment outcomes. Each scoring system has strengths and weaknesses. The ideal system would accurately and reproducibly describe the frequency of incontinent episodes, the degree to which patients are incontinent of gas, liquid, and solid stool, and the effect of incontinence on lifestyle. Two validated scoring systems are widely used: the Cleveland Clinic Continence Score and the St. Mark’s Continence Score. Quality of life scores should be determined independently. Use of the validated Fecal Incontinence Quality of Life symptom-specific score is helpful because it is the patient’s quality of life that is the most important determinant of the need for intervention.

Evaluation of fecal incontinence begins with a detailed interview that includes a careful medical, surgical, and obstetric history. The timing and type of incontinence should be noted, as well as the use of pads, diapers, or medications. It is important to ascertain the severity of the incontinence, which may vary from soiling to loss of a complete bowel movement, and whether the incontinence is primarily associated with urgency and the inability to hold the rectal contents or is passive. Many patients have a combination of symptoms that may include obstructed defecation with incomplete evacuation.

Obtaining a dietary history is important because many patients consume inappropriately high amounts of fermentable fiber in the mistaken belief that a “healthy diet” is required for their bowel condition. Often breakfast is omitted, particularly by working mothers, and thus the opportunity to use the gastrocolic reflex to ensure a predictable early morning bowel movement is lost.

Physical examination should include flexible sigmoidoscopy to rule out neoplastic and inflammatory disorders, with further evaluation of the small and large bowel as clinically indicated. The perineum is inspected for scars, fistulas, and adequacy of the perineal body. The presence of rectal prolapse or perineal descent is appreciated by asking the patient to bear down. Digital examination at rest and with squeeze effort permits qualitative assessment of internal and external sphincter function. The presence and extent of a rectocele or uterine prolapse should be determined.

Endoanal ultrasonography is the best technique currently available to evaluate patients for possible anatomic anal sphincter defects and should be performed in all patients with incontinence. The relationship between the extent of an individual anal sphincter defect and continence is difficult to correlate; however, defects extending to one quadrant (90 degrees) or greater usually contribute significantly to a patient’s symptoms. Defects in the external anal sphincter (EAS) are associated with urge incontinence, whereas internal anal sphincter (IAS) defects are associated with passive soiling and leakage of mucus. Occult anal fistulas and other less common pathologic conditions also may be identified using endoanal ultrasound, and three-dimensional imaging may be useful in assessing the extent of injury. In expert hands, transperineal ultrasonography provides detailed anatomic images and may allow dynamic assessment of rectocele, rectal intussusception, and levator ani injury.

Patients considering surgery because of the severity of their incontinence should undergo anorectal physiologic assessment. Anal manometry documents resting and squeeze pressures, indicating IAS and EAS function, respectively. Rectal sensation may be assessed using balloon distention to determine the volume of first sensation, volume of first urge, and maximum tolerated volume. Pudendal nerve function may be evaluated noninvasively by determining pudendal nerve terminal motor latency with a glove-mounted electrode; however, the results are not predictive of therapeutic outcome, and the technique is not routinely performed. Concentric nerve electromyography of the EAS can accurately determine the presence of motor neuropathy, and the cliteroanal reflex can be used to determine afferent and efferent conduction along the pudendal nerve and its terminal branches. In practice, such investigations are rarely performed.

Defecography provides a dynamic view of rectal function and permits identification of pelvic floor disorders such rectocele or internal intussusception that can contribute to incontinence through obstructed defecation and incomplete evacuation.

Treatment

Treatment should be individualized based on the severity of symptoms, the patient’s overall condition, and the degree to which the incontinence is affecting the patient’s quality of life.