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10/1/2015

Anal Incontinence

Fecal incontinence is defined as the involuntary loss of liquid or solid stool, whereas anal incontinence, commonly termed “accidental bowel leakage” (ABL), also includes the loss of flatus. The prevalence of ABL in large ambulatory populations ranges from 1% to over 20%. The biggest identified risk factors include diarrhea and advancing age.

The anal sphincter complex is made up of the internal (IAS) and external anal sphincters (EAS) that provide both resting and increased voluntary tone of the anal canal. The IAS is a condensation of the circular smooth muscle of the bowel wall that provides 75% of the resting tone and serves as the primary barrier against stool leakage. The EAS is made up of striated muscle and is innervated by the pudendal nerve. The external sphincter and puborectalis muscle provide the voluntary components of fecal continence.

Fecal incontinence may be caused by anatomical abnormalities of the muscle (sphincter or puborectalis), or nerve injury, including the pudendal nerve. Functional factors such as anorectal sensation, stool characteristics including consistency, and medications may affect continence. Anal sphincter weakness may be atraumatic (such as with neurologic disorders) or traumatic, including obstetric injury and pudendal nerve injury. The greatest risk factor for anal sphincter injury is operative vaginal delivery (forceps higher risk than vacuum), followed by primiparity, midline episiotomy, occiput posterior head position, macrosomia, and prolonged second stage. Additionally, rectal urgency is a significant risk factor for fecal incontinence in women.

Evaluation should include a comprehensive medical, surgical, and obstetric history, and a symptom history to distinguish incontinence from urgency, medication effects, and neurologic disease. Questions should include the onset and duration of symptoms, the quality and consistency of the stool that is successfully stored versus leaked, and the patient's bowel habit history. Physical examination includes evaluation of the perianal area and digital rectal examination, as well as assessment of perineal sensation and evaluation of pelvic support. Digital exam may evaluate for sphincter tone and weakness but may not always provide accurate assessment. Potentially helpful diagnostic tests include  endoanal ultrasonography, and anal manometry. Ultrasound effectively evaluates anal sphincter anatomy, while anal manometry provides information about rectal sensation and compliance. Although these tests can be useful in the management of complex patients they are not recommended in the initial management of patients with fecal incontinence. Colonoscopy should be recommended in these patients especially when accompanied by other symptoms such as abdominal pain, rectal bleeding or anemia.

Initial management includes dietary manipulation and bowel schedules, as well as medications to decrease colonic motility (loperamide, diphenoxylate/atropine), and stool bulking agents (psyllium, polycarbophil). More specialized interventions include biofeedback, a vaginal insert with a balloon that obstructs the rectum, sphincter bulking agents, sacral neuromodulation and surgery. Maintaining normal stool consistency and frequency is imperative, regardless of the integrity of the anal sphincter complex. Failure of initial management of these patients should trigger referral to a specialist with experience in managing these disorders.

Sphincteroplasty is reserved for women with evidence of an anatomic defect who do not respond to initial management, Short-term benefit is achieved in over 85% of patients; however, long-term success rates only approximate 50%.

 

Further Reading:

American College of Obstetricians and Gynecologists, ACOG Practice Bulletin No. 210: Fecal Incontinence. Obstet Gynecol. 2019 Apr;133(4):e260-e273. doi: 10.1097/AOG.0000000000003187.

Wald A, Bharucha AE, Cosman BC, Whitehead WE, American College of Gastroenterology, ACG clinical guideline: management of benign anorectal disorders., Am J Gastroenterol. 2014 Aug;109(8):1141-57; (Quiz) 1058. doi: 10.1038/ajg.2014.190. Epub 2014 Jul 15.

Wald A. Diagnosis and Management of Fecal Incontinence. Curr Gastroenterol Rep. 2018 Mar 26;20(3):9. doi: 10.1007/s11894-018-0614-0.

 

Initial Approval: May 2015, Reviewed November 2016, Revised May 2018, Revised November 2019. Revised July 2021, Reaffirmed January 2023

Originally titled: “Fecal Incontinence”.  Title revised July 2021

 

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