Fecal Incontinence

Etiology

Causes of fecal incontinence include: 

• Central nervous system disease or injury
• Autonomic nervous system disease or injury
• Inflammatory bowel disease
• Irritable bowel syndrome 
• Diabetes mellitus 
• Multiple sclerosis 
• Cerebrovascular accident 
• Anal surgery
• Spinal cord trauma
• Vaginal delivery

Epidemiology

The prevalence of fecal incontinence is difficult to estimate because often, this condition is underreported due to social stigma. The overall reported prevalence of fecal incontinence ranges from 2% to 21%, with a median of 7.7%. There is significant variation depending on age. The prevalence of fecal incontinence is reported as 7% in women younger than 30 years, which rises to 22% in their seventh decade. In geriatric patients, prevalence is reported as high as 25% to 35% of nursing home residents and 10% to 25% of hospitalized patients. Fecal incontinence is the second leading cause of nursing home placement in the geriatric population.[2][3]

Overall, it appears that rates of fecal incontinence are on the rise. Following cesarean section, fecal incontinence is very common. Other factors linked to fecal incontinence include advanced age, vaginal delivery, and depression. Additionally, the cost of managing fecal incontinence is enormous. The public spends hundreds of millions of dollars on adult diapers to control fecal and urinary incontinence.

Pathophysiology

Understanding the physiology of continence is important to understand the pathophysiology of incontinence. The anatomical structures that help maintain control of bowel function include:

• Rectum: A stool reservoir that can hold up to 300 mL volume without any increase in pressure. Beyond this limit, an urge to defecate occurs. The rectum is connected with the anus, a 3- to 4-cm hollow muscular tube that lies at a 90-degree angle from the rectum at rest. During defecation, this angle becomes obtuse, about 110 to 130 degrees, allowing for the passage of stool.
• Internal anal sphincter: Innervated by an enteric nervous system, this structure is responsible for 80% to 85% of anal canal resting tone. The anorectal inhibitory reflex allows for the internal sphincter to relax, allowing anal sensory receptors to sense rectal contents. This helps to differentiate solid or liquid stool from gas.
• External anal sphincter: Innervated by the pudendal nerve, this structure contracts and maintains continence during a sudden increase in intraabdominal pressure, such as during coughing or lifting.
• Puborectalis muscle: This muscle forms a sling around the anorectal junction and maintains the anorectal angle, which maintains the anatomical barrier against the discharge of stool.

To maintain fecal continence, there is a complex interplay of several organ systems and nerves. As the fecal mass presents to the rectum, this causes distension. The parasympathetic nerves (S2-S4) transmit the sensation of rectal distension, which induces relaxation of the rectoanal inhibitor reflex and contraction of the rectoanal contractile reflex. The rectal lining has a rich supply of nerve endings that can sample if the mass is liquid or solid. Abnormal sampling and lowered anorectal sensation most likely contribute to fecal incontinence in many individuals. Any pathology that interferes with these processes, like trauma, stroke, vaginal delivery, or paralysis, can result in fecal incontinence.

History and Physical

History

Fecal incontinence can be differentiated as the following 3 different subtypes:

• Passive incontinence: Passive discharge of fecal material without any awareness; indicates neurological disease, impaired anorectal reflexes or sphincter dysfunction
• Urge Incontinence: Inability to retain stool despite active attempts with preserved sensation; indicates sphincter dysfunction or inability of the rectum to hold stool
• Fecal seepage: Undesired leakage of stool often after a bowel movement with normal continence

Essential history to assess underlying etiology in fecal incontinence includes:

• Nature of incontinence (gas, stool consistency), history of urgency
• Onset, duration, timing
• Effect offecal incontinence on quality of life
• History of constipation
• Medication that can cause constipation or diarrhea
• Medical history (irritable bowel disease, diabetes mellitus, thyroid problems, spinal problems, neurological diseases, urinary incontinence)
• Obstetric history in females (use of forceps, perineal tears, number of deliveries)

There are tools for evaluating fecal incontinence based on surveys.

Physical Examination

A detailed neurological exam should be performed to evaluate for neurological disease. A detailed rectal exam is key in the evaluation of fecal incontinence; it can be best divided into the following steps, but the accuracy of the rectal exam and the evaluation of various structures depend to a large extent on the examiner’s experience.

• Inspection: The examiner should check for hemorrhoids, the presence of fecal matter, scars, or skin excoriation; they should also assess for prolapse and excess perineal descent (>3 cm).
• Anal wink reflex: This step can be performed by gently stroking the perianal skin with a cotton ball, which causes brisk contraction of the external anal sphincter. The absence of this reflex indicates a loss of spinal arc and possibly underlying neurological disease.
• Digital rectal exam: A resting rectal tone should be assessed to evaluate the internal anal sphincter. After this, patients should be asked to bear down, during which the function of the puborectalis (to straighten the anorectal angle), as well as pelvic floor muscles, can be assessed. The final step is to ask the patient to squeeze, during which increased pressure due to the contraction of the external anal sphincter is felt. The clinician can also insert a finger in the rectum and ask the patient to tighten the anal sphincter; this gives some idea about the muscle tone.

Evaluation

Diagnostic testing is guided by whether incontinence is related to stool consistency.[4][5] If diarrhea is suspected as a primary reason for incontinence, the following steps should be taken:

• Ordering of stool studies to check for infection, osmolality, fat content, and pancreatic insufficiency
• Evaluation for diabetes and thyroid disorders
• Evaluation for bacterial overgrowth and lactose or fructose intolerance
• Colonoscopy to evaluate mucosal disease (irritable bowel disease or colitis), mass, ulcer, and stricture

If incontinence is without diarrhea, more specific testing should be pursued. The most valuable tests for evaluating fecal incontinence are anorectal manometry and endoscopic ultrasound. Defecography is usually reserved for refractory symptoms or before operative planning intervention.

• Endoscopic ultrasound: To assess the internal and external anal sphincters
  • The test is performed with the patient in the lithotomy or left lateral position, allowing the clinician to measure the thickness of the muscle.
• Magnetic resonance imaging 
• Anal manometry: To assess the resting and squeeze rectal pressure
  • The technique can also be used to assess rectal capacity and compliance.
• Measuring pudendal nerve latency: To assess the integrity of the pelvic floor neuromuscular integrity
• Electromyography
  • This can help assess the electrical activity initiated by the muscle at rest, during voluntary contraction, and after a Valsalva maneuver.
• Defecography: To assess the evacuation of the rectum under fluoroscopy
  • In most cases, contrast is inserted into the rectum, and images are obtained during defecation.

Treatment / Management

Supportive Measures 

The following supportive measures can be implemented for patients with fecal incontinence:

• Anything that improves a patient’s general well-being and nutritional status
• Hygiene maintenance includes avoiding perianal skin soiling with regular cleaning, zinc oxide application, and incontinence pads.
• Avoidance of foods that can provoke diarrhea (eg, a diet high in high lactose or fructose)
• Patients with mild cognitive impairment might benefit from a regular defecation program [6][7][8]
(B3)

Medical Management

The following treatments are directed at improving stool consistency and reducing stool frequency:

• Bulking agents (methylcellulose) may help improve stool consistency.
• Loperamide (Imodium) 4 mg 3 times a day may help reduce stool frequency, improve urgency, increase colonic transit time, and increases anal sphincter resting tone.
• Diphenoxylate (Lomotil) also results in clinical improvement, but objective tests do not improve.
• Including the treatment of other underlying disorders, if suspected, such as bile salt malabsorption, irritable bowel syndrome, and irritable bowel disease is important.
• In postmenopausal women, estrogen replacement therapy might be beneficial.
• In cases of combined urinary and fecal incontinence, amitriptyline might be helpful.

If the above therapy fails, further investigation should be done with anorectal manometry with imaging (endoscopic ultrasound, magnetic resonance imaging).

Biofeedback Therapy

If detected during manometry, they are indicated for patients with impaired external sphincter tone and loss of sensation to rectal distention. Biofeedback therapy is based on the concept of cognitive retraining of the pelvic floor and abdominal musculature to overcome the above defects. Study results have reported a wide range of success rates (from 38% to 100%). This wide variation is due to small-scale studies with methodological limitations and different definitions of outcomes.

Surgery

Surgery is recommended for patients with refractory symptoms that do not respond to the above measures. Surgical approaches can be divided into 4 categories:

• For patients with a simple structural abnormality of sphincters, such as due to obstetric trauma, overlapping sphincter repair might be sufficient. The success rate is 70% to 80%.
• For patients with the anatomically intact but weak sphincter, a postanal approach for augmentation of anorectal angle is performed. The success rate is 20% to 58%.
• For patients with severe structural damage to the anal sphincter, the construction of a neosphincter is performed using either autologous skeletal muscle (gracilis or gluteus) or an artificial bowel sphincter. The success rate is 38% to 90%.
• Rectal augmentation (side-to-side ileorectal pouch or ileorectoplasty) is considered in patients with reservoir or rectal sensorimotor dysfunction.

Recently, injection of silicone has been shown to augment the function of the internal anal sphincter. Others have shown promise with carbon-coated microbeads. Sacral nerve stimulation is a minimally invasive approach for fecal incontinence. The stimulator may benefit patients with minor anal sphincter deficits due to a neurological issue. The 2-step procedure involves initially placing temporary external electrodes into the sacral foramen. The stimulation decreases symptoms of fecal incontinence by enhancing the squeeze and resting anal pressures and colonic motility. Patients who respond then undergo permanent placement of an embedded neurostimulator. While good outcomes have been reported in several study results, the surgery can be associated with hematoma, seroma, and infection. In addition, lead migration and paresthesias are not uncommon. To counter these problems, sacral transcutaneous electrical nerve stimulation is now being evaluated.

Another relatively new method to manage fecal incontinence is the use of an injectable anal bulking agent. The hyaluronic acid derivative is injected into the anal mucosa, and the treatment can be repeated. Early results show that some patients may have a reduction in episodes of fecal incontinence. In 2015, the vaginal bowel control device was approved for fecal incontinence. The vaginal insert has an inflatable balloon that exerts pressure through the vaginal wall onto the rectal area, thus reducing fecal incontinence. The device does need regular cleaning and can be inflated and deflated as needed.

Differential Diagnosis

The differential diagnoses for fecal incontinence includes the following:

• Vaginal or anal foreign body
• Rectovaginal fistula
• Fistula in ano
• Anorectal abscess
• Rectal prolapse

Prognosis

The prognosis for most patients with fecal incontinence is guarded. Short-term outcomes after sphincteroplasty vary from 30% to 60%. In the long term, there are satisfactory results in less than 50% of patients. The quality of life is poor, and mental distress is common.

Complications

Fecal incontinence is a complex issue that is not easy to manage. The vast number of methods used to manage the condition indicates that no method works reliably. Patients with fecal incontinence have enormous mental distress, depression, and anxiety, and their overall quality of life is poor. Complications are mainly related to surgery, which includes:

• Separation of skin and subcutaneous tissue
• Devascularization of vessels leading to necrosis
• Infection
• Bleeding, hematoma
• Fecal and anal pain
• Continued fecal incontinence