Anal incontinence: Diagnosis and Management

Evaluation

Assessment of the woman with FI must include a thorough history because the origin of the problem may be the single most important criterion of therapy. Box 22.3 lists some questions to consider when taking an FI history.

The history should elicit the onset, duration, and severity of the condition; effect on the woman’s daily activities; pad use; frequency and consistency of bowel movements; use of laxatives; fiber intake; and dietary habits. Specific questions concerning diarrhea, amount of flatus, average number of stools per day, passage of mucus, and bloating should be asked. Physicians and patients can define normal bowel function differently. Diarrhea may mean frequent bowel movements to one person but loose and watery bowel movements to another. It is best to have the woman quantitate the number of bowel movements and incontinent episodes and describe the stool consistency. A diary of bowel habits and incontinent episodes can be useful, particularly in women who struggle to provide a clear history ( Fig. 22.3 ). In women who wear pads, these can be inspected to see if that represents her normal amount of leakage. Table 22.2 gives a commonly used scoring system developed by , although there are several other options to consider. The woman circles the appropriate number on each line of the scale. The sum of the lines indicates the severity of FI, with 0 indicating no incontinence and a score of 20 indicating complete incontinence. A score of 4 or more is typically considered significant. The value of this continence grading scale is that it can be used before and after treatment to determine the efficacy of the intervention. A standardized questionnaire should be used whenever possible to assess baseline FI severity and efficacy of treatment.

The history should identify complaints such as feelings of incomplete emptying, straining with bowel movements, fecal urgency, pain with defecation, and insensible loss of stool. It is particularly important to determine whether the woman has FI when she is aware of the need to defecate or if she is unaware and simply finds stool in her undergarments. When stool leakage occurs without warning, a sensory impairment or hygiene problem is implied, whereas if the woman is aware but cannot prevent the passage of stool, a motor impairment is more likely. Soiling may also be due to prolapsing hemorrhoids or rectovaginal or anovaginal fistulas.

Women should be questioned about other pelvic floor pathologic conditions, particularly rectal prolapse, rectovaginal fistulas, and urinary incontinence. Review of systems should include abdominal pain or cramping, lower back or pelvic pain, and changes in sexual response. Changes in pelvic or lower extremity neurologic function or acute onset of FI, in particular, should prompt evaluation for a neurologic disease, such as multiple sclerosis or a neoplasm of the brain or lumbosacral spinal cord.

The medical history is important to establish the state of the woman’s pelvic floor and anal sphincters. It should, when possible, include a detailed history of vaginal deliveries, including birthweights, length of second stage, episiotomies or lacerations, and use of forceps. Any breakdown or complications of episiotomy healing should be noted. Any history of abdominal or pelvic surgeries and/or trauma to the back or pelvis should be reviewed. The operative reports of any rectal or vaginal surgeries should be obtained and reviewed in particular for complications. The results of flexible sigmoidoscopies, colonoscopies, barium enemas, and defecography should be documented. Family history of colon cancer, inflammatory bowel disease, or familial polyposis should be elicited.

Many medications also affect bowel function ( Table 22.3 ). The woman should not only be asked about laxatives and bowel stimulants, but a complete list of all prescription and over-the-counter medications, as well as any dietary or herbal supplements, should be reviewed. Many drugs, including anticholinergics, antidepressants, iron, narcotics, nonsteroidal antiinflammatory drugs (NSAIDs), and pseudoephedrine, can cause chronic constipation that may contribute to overflow incontinence or pelvic floor neuropathy secondary to straining.

Physical examination

The physical examination begins with inspection of the perineum and anal region. Pruritus ani, or discoloration and irritation of the perianal skin, is commonly seen with FI of liquid stool and chronic diarrhea. Perianal skin creases or folds should completely encircle the anus. Note the presence of protruding tissue around or from the anus and determine whether there are external hemorrhoids or mucosal or full-thickness rectal prolapse ( Fig. 22.4 ). The dovetail sign, or loss of anterior perineal folds, indicates a defect in the EAS or chronic third-degree laceration ( Fig. 22.5 ). Previous episiotomy, laceration, or surgical scars should be noted. The size of the genital hiatus and presence of genital prolapse should be assessed as an indicator of pelvic floor neuromuscular function. Eliciting the clitoral-anal or bulbocavernosus reflex can grossly test the innervation of the EAS. Using a cotton swab, a gentle, quick touch beside the clitoris or over the bulbocavernosus muscle should elicit a contraction of the EAS. If intact, the reflex implies that the pudendal afferent nerves and rectal or external hemorrhoidal branch of the pudendal efferent nerves are functional; however, 10% of women lack this reflex naturally. If absent in the presence of FI, though, further neurologic testing is suggested. Sensation in the S2-S4 dermatomes should be screened by dull and pinprick discrimination when touching the perineum. The same wooden cotton swab used to elicit bulbocavernosus reflexes can be broken and then used for pinprick (broken end) and dull (cotton end) sensation testing. Loss of sensation should direct the clinician to further neurologic or radiologic assessment of the nervous system.

Next the woman should be asked to squeeze as if trying not to pass gas. The perianal folds should be evaluated for a concentric contraction and some upward movement of the perineal body as she contracts the EAS and levator ani; the patient should be instructed not to compensate by using contraction of the buttocks, upper thighs, or abdomen. The woman should then be asked to bear down as if trying to have a bowel movement. She should be reassured that it is expected that she might pass flatus during this part of the examination. The degree of perineal descent and any prolapse of the vagina, pelvic viscera, or rectum should be noted. If there appears to be any pelvic organ prolapse or if the degree or type of prolapse the woman complains of cannot be seen in the supine position, the examination should be performed with the woman in the standing position or after straining on a commode to maximize the prolapse.

Rectal examination is used to assess resting and squeeze tones of the anal canal. The resting tone of the anal canal is an indicator of IAS function. During squeezing of the EAS the examiner should feel circumferential contraction and tightening. An upward movement of the rectum and posterior compartment of the pelvis should be seen as the levator ani muscles contract. Because these muscles also play an important role in anal continence, evaluation of the levators for strength and symmetry should be performed by palpating the muscles on each side of the vagina at the introitus. Women with a history of vaginal delivery will often have a noticeable asymmetry because this portion of the levator is the most commonly injured. While doing the rectal examination, the presence of a rectocele, enterocele, rectal prolapse, or bowel intussusception should also be assessed as the woman strains. With a finger in the rectum and another in the vagina, the integrity of the rectovaginal septum, posterior vaginal wall, and perineal body can also be evaluated.

The anal canal and rectum should also be palpated for masses, a dilated rectum, and the presence of stool in the rectal vault. As noted earlier, a rectum chronically distended with stool, a tumor, or an intussuscepting bowel will disrupt the RAIR. If this reflex is suppressed, the anal canal remains dilated, the EAS fatigues, and incontinence can occur.

Testing

Clinical diagnosis based on physical examination and history alone will be sufficient in most women; however, a prospective study at a tertiary colorectal referral clinic found that further evaluation, including radiologic and physiologic tests, altered the final FI diagnosis in 19% of cases. The algorithm outlined in Fig. 22.6 recommends further evaluation based on history and the rectal tone. Normal rectal tone directs the clinician away from anal incontinence and toward a metabolic or colonic origin. Common metabolic tests include thyroid-stimulating hormone and glucose levels. If chronic diarrhea is present with normal rectal sphincter tone, stool cultures, colonoscopy, and diarrhea evaluation are suggested. The differential diagnosis for a diarrhea workup includes the following:

• Lactose intolerance

• Celiac sprue

• Inflammatory bowel disease

• Irritable bowel syndrome

• Bacterial overgrowth from diabetic gastroparesis

In cases of FI with normal rectal sphincter tone without diarrhea, anal manometry to evaluate rectal sensation may be useful to assess for peripheral neuropathy causes.

Poor resting tone on rectal examination directs the clinician to a neuromuscular cause. A normal resting tone, but with poor squeeze, suggests an anterior sphincter defect and chronic third-degree laceration of the EAS. If poor rectal squeeze is detected, endoanal ultrasonography is the considered the best method to assess for a disrupted EAS.

Evaluation or further testing is performed not only for diagnostic purposes but also to determine which nonsurgical and surgical therapies are most likely to benefit the woman. Whenever the woman’s history does not match her physical examination findings, further testing should be considered. In addition, if the woman has had prior surgery or has other pelvic floor dysfunction, testing before treatment, especially surgical, may help clarify the optimal care plan. It is important to remember that the woman may have more than one pathologic process contributing to her FI, such as pudendal neuropathy and an anal sphincter defect in combination with a weakened pelvic floor and diarrheal state ( Table 22.4 ).

Diagnostic procedures

Endoanal ultrasound

Endoanal ultrasound (EAUS) has significantly enhanced the ability to delineate defects of the IAS and EAS. It is one of the simplest and least expensive tests for imaging sphincter defects; however, it is user dependent and requires significant training. EAUS is generally performed with a 10-MHz rigid probe that creates a 360-degree circular image of the anal sphincter complex, allowing assessment of the integrity, thickness, and length of the anal sphincter complex. The IAS is visible as a hypoechoic circle, and the EAS is seen as a hyperechoic or mixed echogenic circle ( Fig. 22.7 ). The distal anal canal is characterized by the presence of the EAS but a thin or absent IAS. In the mid–anal canal the IAS and EAS are both robust, whereas the proximal anal canal is characterized by the posterior sling of the puborectalis. EAUS can also be used to determine the size of the perineal body by using a gloved finger inserted into the vagina to oppose the rectovaginal septum against the probe.

EAUS is most useful in the evaluation of women with chronic third-degree lacerations or for suspicion of occult sphincter tears ( Fig. 22.8 ). Knowing the boundaries of the sphincter defect and whether both the EAS and IAS are disrupted can direct the surgeon at the time of anal sphincteroplasty if that is indicated.