Anal Incontinence

Introduction

• Description: Anal incontinence is the recurrent involuntary passage of solid or liquid fecal material or flatus. Anal incontinence may be further divided into urge incontinence (incontinence occurs despite efforts to retain stool) and passive (the lack of awareness before the incontinent episode). Anal incontinence can result from damage or dysfunction of the anal sphincters, abnormal rectal compliance, decreased rectal sensation, altered stool consistency, or a combination of these.

• Prevalence: Between 7% and 15% of the population (>5.5 million Americans), up to 43% of acutely ill hospital patients and 70% of nursing home populations. It is the leading cause of admission to nursing homes. Women are affected at rates that are slightly higher than those for men (primarily due to increased life expectancy and obstetric trauma).

• Predominant Age: Incidence increases with age (2.6% adults aged 20–29 years, 15.3% adults aged ≥70 years)

• Genetics: No genetic predisposition.

Etiology And Pathogenesis

• Causes: Normal sphincters and pelvic floor; diarrhea, infection, inflammatory bowel disease; anatomic derangements and rectal disease—congenital abnormalities, fistula, rectal prolapse, anorectal trauma (including obstetric), surgery (hemorrhoidectomy), Crohn disease; neurologic disease—central disease (dementia, sedation, stroke, brain tumor, spinal cord lesions, multiple sclerosis, tabes dorsalis, back surgery), peripheral disease (cauda equina lesions, polyneuropathies, diabetes mellitus, Shy-Drager syndrome, toxic or traumatic neuropathy, fecal impaction, delayed-sensation syndrome); skeletal muscle disease—myasthenia gravis, muscular dystrophy, smooth muscle dysfunction; proctitis (inflammatory bowel disease)—radiation proctitis, rectal ischemia, fecal retention or impaction, internal sphincter weakness, diabetes mellitus. Multiple factors may exist at the same time.

• Risk Factors: Traumatic injury (anal surgery, obstetric lacerations, operative vaginal delivery, high-birthweight infant, a long second stage of labor, and occipitoposterior presentation of the fetus, anal intercourse), neurologic disease, infectious or other diarrhea, irritable bowel syndrome, older age, diabetes mellitus, postmenopausal hormone therapy. Medications such as metformin, antibiotics, antacids, laxatives, and proton pump inhibitors increase the risk.

Signs And Symptoms

• Variable large, uncontrolled, loose bowel movement

• Involuntary loss of stool or flatus

• Fecal staining of undergarments

Diagnostic Approach