Fecal incontinence (FI) is the involuntary passage of fecal matter through anus or inability to control the discharge of bowel contents. Its severity can range from an involuntary passage of flatus to complete evacuation of fecal matter. Depending on the severity of disease, it has a significant impact on patient’s quality of life.
Central nervous system (CNS)
Autonomic nervous system (ANS)
Inflammatory bowel disease (IBD)
Irritable bowel syndrome (IBS)
Diabetes mellitus (DM)
Multiple sclerosis (MS)
Cerebrovascular accident (CVA)
The prevalence of FI is difficult to estimate because often, this condition is underreported due to social stigma. The overall reported prevalence of FI ranges from 2% to 21% with a median of 7.7%. There is significant variation depending on age. Prevalence of FI is reported as 7% in women younger than 30 years which rises to 22% in their seventh decades. In geriatric patients, prevalence is reported as high as 25% to 35% of nursing home residents and 10% to 25% of hospitalized patients. In fact, FI is the second leading cause of nursing home placement in the geriatric population.
It is vital to understand the physiology of continence to understand the pathophysiology of incontinence. The anatomical structures which help to maintain control of bowel function are the following:
Rectum as a stool reservoir and can hold up to 300 ml volume without any increase in pressure. Beyond this limit, urge to defecate occurs. The rectum is connected with anus which is a 3 cm to 4 cm hollow muscular tube which at rest lies at 90-degree angle from the rectum. During defecation, this angle becomes obtuse, about 110 to 130 degrees allowing for the passage of stool.
Internal anal sphincter which is innervated by an enteric nervous system 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 pudendal nerve, contracts and maintains continence during a sudden increase in intraabdominal pressure such as during coughing or lifting.
Puborectalis muscle forms a sling around the anorectal junction and maintains the anorectal angle which maintains the anatomical barrier against discharge of stool.
History and Physical
Fecal incontinence can be differentiated as the following three 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 FI include:
Nature of incontinence (gas, stool consistency), history of urgency
Onset, duration, timing
Effect of FI on quality of life
Medication which can cause constipation or diarrhea
Medical history (IBD, DM, thyroid problems, spinal problem, neurological diseases, urinary incontinence)
Obstetric history in female (use of forceps, perineal tears, number of deliveries).
A detailed neurological exam should be performed to evaluate for neurological disease. A detailed rectal exam is a key in the evaluation of FI; it can be best divided into following steps, but the accuracy of rectal exam and evaluation of various structures depend to a large extent on examiner’s experience:
Inspection: Examine for hemorrhoids, the presence of the fecal matter, scars, skin excoriation. Also, assess for prolapse and excess perineal descent (more than 3 cm).
Anal wink reflex: Can be done by gently stroking perianal skin by cotton bud which will cause brisk contraction of the external anal sphincter. The absence of this reflex indicates loss of spinal arc and possibly underlying neurological disease.
During the digital rectal exam, a resting rectal tone should be assessed to evaluate internal anal sphincter. After this patient should be asked to bear down during which function of 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 contraction of the external anal sphincter is felt.
Diagnostic testing is guided by whether incontinence is related to stool consistency.
If diarrhea is suspected as a primary reason for incontinence:
Stool studies for infection, osmolality, fat content and pancreatic insufficiency
Evaluation for diabetes and thyroid disorder
Evaluate for bacterial overgrowth and lactose/fructose intolerance
Colonoscopy to evaluate for mucosal disease (IBD/Colitis), mass, ulcer, and stricture.
If incontinence is without any diarrhea then more specific testing should be pursued. The most valuable tests for the evaluation of FI are anorectal manometry and endoscopic ultrasound. Defecography is usually reserved for refractory symptoms or before operative planning intervention.
Endoscopic Ultrasound (EUS)
Magnetic Resonance Imaging (MRI)
Treatment / Management
Supportive measures to improve patient’s generalized well-being and nutritional status
Avoid food which can provoke diarrhea (high lactose/ fructose diet)
Patient with mild cognitive impairment might benefit from regular defecation program.
Directed at improving stool consistency and reducing stool frequency
Bulking agents (methylcellulose) to improve stool consistency
Loperamide (Imodium) 4 mg three times a day to 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
Treatment of other underlying disorders if suspected such as bile salt malabsorption, IBS, and IBD
In post-menopausal women, estrogen replacement therapy might be beneficial
In cases of combined urinary and fecal incontinence, amitriptyline might be helpful.
If above therapy fails, further investigation should be done with anorectal manometry with imaging (EUS/MRI).
Indicated for patients with impaired external sphincter tone and loss of sensation to rectal distention if detected during manometry. Biofeedback therapy is based on the concept of cognitive retraining of pelvic floor and abdominal musculature to overcome above defects. Studies report a wide range of success rate ranging from 38 % to 100%. This wide variation is due to small-scale studies with methodological limitation with a different definition of outcomes.
In patients with refractory symptoms that do not respond to above measures.
Surgical approaches can be divided into four categories:
For patients with the 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 anatomically intact but weak sphincter, post anal 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, construction of neosphincter is performed using either autologous skeletal muscle (gracilis or gluteus) or artificial bowel sphincter. The success rate is 38% to 90%.
Rectal augmentation (side to side ileorectal pouch or ileo-rectoplasty) is considered in patients with the reservoir or rectal sensorimotor dysfunction.