Etiology
Functional fecal incontinence associated with chronic constipation and severe fecal impaction
The child has no underlying anatomical abnormality, but the severe fecal impaction leads to dilatation of the rectum.
Chronic dilatation leads to decreased rectal sensation, so the child has less urge to defecate.
Softer stool forms above the hard impaction, and the softer stool leaks around the hard stool, known as "overflow."[1]
Functional nonretentive fecal incontinence
The exact etiology is unknown, but possible contributing factors include psychological, behavioral, or emotional disturbances, genetics, and decreased motor function and sensation in the gastrointestinal tract.
Etiology is likely to be multifactorial.[10]
Organic fecal incontinence
Anatomical abnormalities of the gastrointestinal tract or neurological denervation of the gastrointestinal tract leads to inability to control bowel movements.[11]
The child has either an underlying anatomical abnormality (e.g., anorectal malformations, spinal and neurological abnormalities, or postsurgical abnormality) that causes the lack of bowel control, or a medical condition (e.g., hypothyroidism, celiac disease, or cystic fibrosis) that may result in fecal impaction with overflow incontinence.
Medication overuse
Rarely, fecal incontinence may be due to overuse of medication (i.e., laxatives or orlistat) used mainly by adolescents and adults.
Pathophysiology
Fecal continence requires normal gastrointestinal and neurologic structures and functions involved in the proper functioning of anal sphincters, muscles, and nerves controlling the gastrointestinal tract. Any underlying process that disturbs the normal functioning of the anatomical structures involved in maintaining fecal continence will cause fecal incontinence.
Functional fecal incontinence associated with chronic constipation and severe fecal impaction: a cycle of constipation and the formation of large, painful bowel movements leads to maneuvers to prevent defecation, such as tightening of gluteal muscles. Fecal impaction of hard stool results, and softer stool flows around the impacted fecal mass and leaks from the distended rectum, which is desensitized to the sensation of needing to defecate.
Functional nonretentive fecal incontinence: the exact pathophysiology is unknown but, by definition, the child does not have fecal retention or an inflammatory, anatomical, metabolic, or neoplastic process that explains the fecal incontinence.[1]
Organic fecal incontinence: the exact etiology of fecal incontinence depends on the underlying cause. Examples include the following:
Anorectal malformations are associated with abnormal puborectal musculature and anal sphincters, and abnormal anal sensation.
Children with spinal and neurological abnormalities may also have dysfunctional bowel motility and abnormal anal sensation.[3]
Fecal incontinence following surgery for Hirschsprung disease may be secondary to resultant abnormal sphincter function, abnormal sensation, loss of rectocolonic inhibitory reflex, or overflow incontinence due to constipation.[12]
Hypothyroidism may result in chronic constipation with subsequent fecal retention and overflow incontinence.
In children presenting with a more recent onset of constipation and fecal retention, anal fissure may be a contributing factor to the continued constipation.
Cystic fibrosis and celiac disease may present with increased stool frequency and diarrhea.
Classification
Functional fecal incontinence associated with chronic constipation and severe fecal impaction
The child has no underlying anatomical abnormality but experiences overflow soiling due to chronic constipation and severe fecal impaction.[1]
Functional nonretentive fecal incontinence
The child has no fecal impaction or underlying anatomical abnormality or medical condition and experiences fecal incontinence for unclear reasons.[1]
Organic fecal incontinence
The child has an underlying anatomical abnormality (e.g., anorectal malformations, spinal and neurological abnormalities, or postsurgical abnormality) or medical condition (e.g., hypothyroidism) that causes the lack of bowel control.[2][3]
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