PATHOPHYSIOLOGY
Once a child withholds stool rather than passing stool, the colon begins to distend. This distention gradually stretches nerve fibers, and over time, the child has less and less sensation of the urge to pass stool. The stools become larger and larger, and the child becomes less able to feel or pass the stool voluntarily. The large stool becomes impacted, with loose, watery stool leaking around the impaction, causing the appearance of uncontrollable diarrhea. Eventually, if left untreated, the child cannot control when the large, impacted stool is passed, resulting in incontinence or soiling of large stools in the toilet.
Encopresis in children is classified as organic (nonfunctional), which is related to an anatomic, neurologic, or metabolic cause, or nonorganic (functional), which is related to behavioral or psychological causes.
Causes of organic encopresis include post-surgical anal or rectal stricture, dehydration, megacolon, anorectal fissures or stenosis, laxative use, diarrhea, Hirschsprung disease, spina bifida, hypothyroidism, hype
rcalcemia, cerebral palsy, myelomeningocele, and adverse drug reactions.
Nonorganic encopresis can be caused by ineffective bowel training and psychosocial stressors (e.g., new school, birth of a sibling, repeated sexual abuse). Some children with nonorganic encopresis avoid defecating appropriately (e.g., in a bathroom using the toilet, painful or unpleasant bowel movement) because of fear or anxiety; others intentionally defecate inappropriately because of a mental disorder (e.g., conduct disorder, oppositional defiant disorder, obsessive compulsive disorder, and cognitive delays and learning disabilities).
Other risk factors include eating a high-fat diet, high intake of sugary fluids (such as soda pop, juices), low intake of dietary fiber, low activity level, and/or chronic and/or recurrent stress, specifically an unstable or unpredictable daily routine. Both organic and nonorganic encopresis can produce low self-esteem, aggression, and acting out. Children can fear rejection and social isolation by their peers, and angry and punitive reactions from their parents.