The causes of fecal incontinence are divided into factors that alter anorectal anatomy (trauma, surgery), overwhelm physiologic control mechanisms (diarrhea, secretory tumors, fecal impaction), or interfere with neurologic function (diabetes, spinal cord injury, pudendal nerve injury). In many cases, a combination of factors leads to incontinence ( Table 31-1 ). For example, incontinence associated with rectal prolapse is due to excessive physical stretching of both the anal sphincter and pudendal nerves. Similarly, diminished sphincter strength associated with aging can unmask a previously well-compensated obstetric sphincter injury.
Initial evaluation of the incontinent patient is performed in the physician's office and requires only careful elicitation of pertinent history and performance of a directed physical examination. At the end of this process, the presumed cause of incontinence will be clear in the majority of patients. However, physical examination can fail to indicate the cause of fecal incontinence. Pudendal nerve injury is not in and of itself visible, and sphincter injury due to surgery or childbirth can be undetectable on later examination after healing has occurred. Laboratory evaluation is used to confirm the initial clinical impression, quantify the severity of the physiologic deficit, identify specific anatomic abnormalities, and elucidate the causes of incontinence when the diagnosis is obscure or there are multiple abnormalities.
Fecal incontinence is embarrassing, and many patients are reluctant to discuss their condition or even identify it by name. Accordingly, one of the first steps in evaluating the incontinent patient may be getting the patient to admit to the problem. Many patients present with complaints of "diarrhea," which on close questioning turns out to be involuntary loss of normal stool. It is also common for a patient to complain of the sudden onset of fecal incontinence and, on careful questioning, reveal that a change in stool consistency
preceded the onset of incontinence. Certain risk factors or associated conditions should alert the physician to the presence of fecal incontinence: anal trauma or surgery;1 • vaginal deliveries,1 • especially multiple, difficult, or traumatic ones; pelvic radiation;1 • 1 • diabetes mellitus, especially with neuropathy; chronic diarrheal states; congenital conditions,1 • such as imperforate anus and spina bifida; urinary flli 
incontinence; or complaints of rectal prolapse or anal protrusion.1 • 1 •
The extent of incontinence should also be quantified. The key components of severity assessment include the nature of the material being lost (flatus, liquid stool, or solid stool), the frequency of loss, and the need to wear a pad. Although it is agreed that solid stool incontinence reflects a greater degree of physiologic impairment than incontinence for liquid stool only, it is noteworthy that patients perceive liquid stool
incontinence to be more of a problem because it is more difficult to manage. Numerous scoring systems have been proposed for the evaluation of incontinence, but all have flaws and none are universally accepted. 1 •
Quality-of-life assessment is a critical component to the evaluation of fecal incontinence and the success of its management. The concept itself is obvious, but quantification has proved to be difficult. General scales such as the SF-36 have not proved to be sufficiently sensitive to reflect real changes in patient status. Several incontinence scales combine a subjective quality-of-life assessment with a quantitative severity
score to produce a single global incontinence score, an approach that, despite providing a single score per patient, combines two distinctly separate variables. A newly devised incontinence-specific scale was validated and should bring uniformity and objectivity to quality-of-life assessment.1 ' Physical Examination
Physical examination of the patient with fecal incontinence begins with external examination of the perianal area. Profuse incontinence, particularly of liquid stool, can lead to excoriation of the surrounding perianal skin. The perianal area should be inspected for scars from previous trauma, episiotomies, or anal surgery. The "keyhole deformity" is a groove in the anal canal, most commonly seen in the posterior midline, caused by a sphincterotomy, fissurectomy, or fistulotomy, that permits seepage of stool or mucus. The female patient with an obstetric injury may have a thin perineal body, an associated rectovaginal fistula, or a cloaca due to loss of the rectovaginal septum.
The patient with rectal prolapse may have a visibly patulous anus or one that gapes with traction. The prolapse itself, with its characteristic concentric folds, can be demonstrated by asking the patient to bear down, optimally while seated on a commode. Rectal mucosal prolapse, characterized by radial folds, can cause mucus seepage and staining but is not a cause of more severe incontinence. The anocutaneous reflex is a test of perianal sensation that is elicited by stroking the perineal skin and observing an anal "wink" due to sphincter contraction. This spinal reflex has its afferent and efferent pathways in the pudendal nerve and is abolished if S4 is transected.
The findings to note on digital examination are the tone of the anal canal, the strength of the squeeze, and whether it seems symmetric. A strong contraction of the gluteal muscles should not be confused with contraction of the external anal sphincter muscle. Voluntary contraction of the external anal sphincter normally fatigues to a basal level over 3 minutes. A more rapid fatigue may be elicited in the incontinent patient.
1 • Puborectalis function is evaluated separately from the external anal sphincter; its contraction is detected by an anterior pull on the examining finger emanating from the top of the anal canal posteriorly. Fecal impaction leading to overflow incontinence should be evident on the initial digital examination. If there is a history of obstetric trauma, the examiner should palpate for a rectal vaginal fistula along with assessment of the perineal body width. Obstetric tears usually occur in the anterior midline, leaving a thin perineal body due to retraction of the sphincter muscle posterolaterally. A rectocele is present if there is a weakness in the rectovaginal septum that allows a digit placed in the rectum to push into the vagina. If a large rectocele is present, the posterior wall of the vagina can be pushed out the introitus.
The anoscope is used to look for prolapsing hemorrhoids, scarring in the anal canal from previous surgery, internal fistula openings, and mucosal inflammation. Any patient under evaluation for fecal incontinence should undergo a flexible sigmoidoscopy to exclude proctitis, cancer, or a benign secretory tumor such as a large rectal villous adenoma. A full colonic or small bowel evaluation is not usually necessary unless there is a history of diarrhea in addition to incontinence.
In the majority of patients, the history and physical examination determine the cause of fecal incontinence. For the patient with a minor degree of fecal incontinence, medical management is instituted and further testing can be deferred. For most patients, testing at an anorectal physiology laboratory documents the degree of dysfunction, fully determines anatomic defects, and better directs the treatment plan.1 • 1 •
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