Constipation and Encopresis in Childhood

Abstract

Constipation is a very common frustration for children, parents, and physicians. It is reported to account for nearly 5% of all outpatient visits to pediatric clinics and more than 25% of all referrals to pediatric gastroenterologists. Painful defecation and encopresis (involuntary passage of stool from the anus) usually are the first manifestations noted. Constipation generally is defined by the hard nature of the stool, the pain associated with its passage, or the failure to pass three stools per week. It would be preferable to define constipation as the failure to evacuate the lower colon completely with a bowel movement. This allows the parents and physician to realize that a child who has three small stools daily may not yet have evacuated the colon, while a child who has two large soft stools a week may not be constipated.The frequency of stools in most children decreases from a mean of four per day in the first week of life to 1.7 per day by the age of 2 years. Over this interval, stool volume increases more than tenfold while maintaining a consistent water content of approximately 75%. Peristaltic activity in the colon has been demonstrated as early as the eighth fetal week, with normal colonic haustra seen by 12 weeks. Intestinal transit time from mouth to rectum increases from 8 hours in the first month of life to 16 hours by 2 years of age to 26 hours by the age 10.Normal continence is maintained by the resting tonicity of the internal anal sphincter and can be enhanced by contraction of the puborectalis muscle,which creates a 90-degree angle of rectum to the anal canal. When more than 15 cc of stool enters the normal rectum, stretch receptors and nerves in the intramural plexus are activated. Inhibitory interneurons decrease the resting tone in the involuntary smooth muscle of the internal anal sphincter, relaxing the sphincter and allowing stool to reach the external anal sphincter that is composed of voluntary skeletal muscle. The urge to defecate is signaled. If the child relaxes the external anal sphincter, squats to straighten the anorectal canal, and increases intra-abdominal pressure with the Valsalva maneuver, the rectum is evacuated of stool. If, however, the child tightens the external anal sphincter and the gluteal muscles, the fecal mass is pushed back into the rectal vault and the urge to defecate subsides. Repetitive denial of evacuation leads to stretching of the rectum and eventually of the lower colon, producing a reduction in muscle tone and retention of stool. The longer the stool remains in the rectum, the more water is removed, and the harder the stool becomes to the point of impaction.Encopresis or fecal soiling usually is the result of looser stool leaking or overflowing from a rectum that has been distended by retained stool. Encopresis is three to six times more common among males than females and is acknowledged in 3% of 4-year-olds and 1.6% of 10-year-olds. The child is not aware of the soiling until it is nearly complete, an observation confirmed by anorectal motility studies that document decreased sensitivity to distension in a chronically distended rectum. Although encopresis presents predominantly between 3 and 7 years of age, in one study, 35% of the children had hard stools within the first 6 months of life, 40%experienced delays in toilet training, and 60% reported painful stools before the age of 3 years.More than 90% of chronic encopresis occurs in the context of functional fecal retention, but two forms of encopresis are not associated with fecal retention. Organic incontinence can occur in children who have damaged corticospinal pathways such as lumbosacral myelomeningocele. Other children have anorectal dysfunction after operative pullthrough surgery for high imperforate anus or colectomy. Incontinence also occurs in children who have diarrhea because pelvic floor muscles fatigue in less than 1 minute of continuous contraction above resting tone as they try to hold in a loose stool. The second form of encopresis is functional—the voluntary or impulsive passage of variable volumes of stool into the diaper or clothes. This may result from simple anxiety and the desire to continue diaper use or from more severe passive-aggressive behavior in the context of emotional impulsivity. It is critical to recognize that these children do not have underlying constipation or fecal retention and that laxative therapy could be detrimental. Psychological counseling may be equally valuable in all forms of encopresis because the stress of soiling is independent of etiology.The functional and nonfunctional etiologies of constipation are listed in part in Table 1. It is impossible to discuss all of these in detail, but a few clinical points will be reviewed. A very complete review of Hirschsprung disease was published in Pediatrics in Review in January 1995.Straining with the passage of soft stool is normal in neonates and infants. It is related to their inability to coordinate pelvic floor relaxation with the Valsalva maneuver and to straighten the anorectal canal when lying down. More erratic stooling patterns are reported in infants who have gastroesophageal reflux. Although breastfed infants often have multiple loose stools each day, it is equally normal to have only one a week. The introduction of a formula supplement or rice cereal may reduce stool frequency and increase consistency quickly. Insertion of a glycerin suppository or rectal stimulation with a lubricated thermometer will induce reflex anal sphincter relaxation and the desired evacuation, but regular rectal manipulation is discouraged. If the stools become firm balls or rectal fissures evolve, softening of the stool is indicated. This often can be accomplished by substituting barley cereal for rice; by using a nondigestible sugar such as fructose, sorbital (prune juice), or lactulose; or by introducing higher fiber vegetables into the diet. Mineral oil is not used in infancy, and corn syrup is a less effective osmotic agent because older infants can digest it. Honey should be avoided because of the risk of botulism, a theoretic risk with corn syrup as well. The concerns of most parents and physicians can be addressed by eliciting a careful history and family history and performing a physical examination that includes perineal and rectal examination followed by education and reassurance about the normal variation of infantile stool patterns. Generally, the passage of a large soft stool at intervals of less than 72 hours in infants is not associated with rectal fecal retention.Functional fecal retention is the most common explanation for childhood constipation. As noted previously, voluntary tightening of the external anal sphincter and contraction of the gluteal muscles prevent the passage of stool. This may be initiated solely as a “control” issue with unsuccessful toilet training, the logical response to painful stools in the context of anal inflammation from fissures, perianal streptococcal infection,perianal abscess, or a perceived threatening event such as a television show,birth of a sibling, or desire to avoid defecation in a strange toilet when away from home. Some toddlers and older children (especially those who have attention deficit hyperactivity disorder) are too distracted to evacuate.The resulting distension produces a variety of symptoms from gaseous distension to delays in evacuation of up to 1 week or more. Enormous stools to the point of being “toilet-plugging-specials” are passed with significant pain and a prepassage ritual of gluteal tightening and posturing so dramatic that parents may videotape the performance to be sure the doctor“knows how bad this is.” Other symptoms of increasing fecal accumulation in the colon include early satiety, desire to eat small volumes all day, increasing irritability, and unpredictable spasms of abdominal pain usually located in the lower abdomen. Encopresis becomes increasingly frequent. Painless rectal bleeding from internal anal fissures also may be noted on the surface of stools or on the toilet tissue after defecation. After the passage of an enormous stool, symptoms generally resolve for a few days, then recur.A rectal examination confirms normal anal tone with a massive rectal ampulla filled with formed stool. Abdominal examination may reveal palpable stool in a dilated lower colon. Toddlers who have functional fecal retention cannot be toilet trained until the fear of pain has been allayed and normal rectal sensation has been restored. Interestingly, the constipated toddler who refuses toilet training has no greater frequency of other behavioral concerns than other toddlers. Successful management requires complete evacuation of the colon, sustained evacuation by a “motivational” technique that uses laxatives in younger children and lower dose laxatives with behavioral modification in older children as well as stool softening by dietary fiber,mineral oil, or lactulose. Relapse rates are high and require close follow-up.Irritable bowel syndrome is manifested in some children by intermittent passage of firm stool in painful bowel movements. In contrast to functional fecal retention, the constipation of irritable bowel syndrome is not associated with distension of the colon but with spasm in a colon of normal calibre. Encopresis is rare, and management is based on increased dietary fiber rather than laxatives.Hirschsprung disease or aganglionosis occurs in 1 in 5,000 births. The male-to-female ratio is 4 to 1, and the incidence increases with longer segments of disease. The diagnostic lack of ganglion cells in the myenteric and submucosal plexus of the bowel wall extends proximally from the internal anal sphincter. Among 80% of the involved children, the aganglionic segment does not extend above the sigmoid, while the entire colon and some small bowel may be involved in 3%. The aganglionic bowel has thickened nerve fibers staining for acetylcholinesterase, offering a second pathologic feature on histologic examination. The aganglionic segment of bowel fails to relax because of the absence of inhibitory neurons containing nitric oxide and vasoactive intestinal polypeptide. Thus, difficulty with evacuation is present from birth; meconium is not passed in the first 48 hours of life in 40% of involved infants.Recurrent abdominal distension, emesis, failure to thrive, and acute enterocolitis allow diagnosis of 60% of patients by 3 months of age.The presence of early obstructive features, onset in infancy, and nearly complete absence of encopresis distinguish Hirschsprung disease from functional fecal retention. On rectal examination, the aganglionic bowel is tight around the finger and the rectal ampulla is not dilated. A barium enema usually allows visualization of the transition zone between the tonically contracted aganglionic segment and the dilated proximal bowel. The enema should be performed without preparation, which distorts the distal anatomy. Manometric studies of the rectum demonstrate the failure of the internal anal sphincter to relax when distended. Confirmation of the diagnosis requires rectal biopsy that employs a suction technique for screening and full-thickness technique for definitive operative decisions.Hirschsprung disease is a heterogenous genetic disorder with risk rates for siblings ranging from 3% with short segment disease to 25%with a female who has long segment disease. An autosomal dominant form occurs with mutation in the RET gene. Syndromes associated with Hirschsprung disease include trisomy 21, deletion of chromosome 13q, Smith-Lemli-Opitz,Waardenberg, Laurence-Moon-Biedl-Bardet, congenital deafness, and congenital central hypoventilation.Neuronal dysplasia, in contrast to aganglionic disease, is associated with increased numbers of ganglion cells (hyperganglionosis) in the lower colon. It may present throughout childhood with variable constipation or features of pseudo-obstruction. It is more frequent among children who have neurofibromatosis and has been associated with multiple endocrine neoplasia type IIb due to glioneuromas of the intestinal tract. Surgical intervention is individualized and based on the severity of symptoms and manometric demonstration of severely impaired rectal relaxation.Reduced numbers of ganglion cells (hypoganglionosis) usually is an acquired disease of ganglion seen in disease or in ganglion numbers have been reported in some children who have congenital short and obstructive present in infancy, such as congenital anal and small are acquired in anus is defined by a of the anal based on the ratio of the to the being less than in females and less than in On rectal examination, the creates a rectal that increases with distension of the Surgical is but most patients do well distension of the ampulla is presents with painful constipation in A or is noted on rectal examination with a dilated ampulla above it. The usually to but of the is a to sphincter has been to all of may with small bowel constipation. The form is in with failure to thrive, distension, and with and or acquired forms of a variety of and on the of the clinical physical features, or each eventually can be In children who have disease, or the of and constipation becomes have had children who had demonstrate failure to with only to the intestinal manifestations when confirmed and the or rectal pain and encopresis have been as the of childhood but are other is acknowledged in more than 40% of children who have encopresis and be In the when the pelvic mass of retained rectal stool is allowing the to A greater is the that dilated lower colon in increased frequency of and of the dilated lower colon may tone to allow internal or which may as rectal after evacuation of soft stool. internal creates an of the rectal wall rectal which presents with independent of the of the associated stool. The of the colon by firm stool may to syndrome is seen with associated with increased and the of encopresis can be very to children who have chronic encopresis will an of the when and may the from the is an in the to constipation in diagnosis is but the of an is diagnostic is of greater than the It with the history of of passage of and of early Constipation with from to formula and from to the introduction of is the most of the diet. to child and of with of also may be The of is from diaper to toilet training and is the time for history is for of genetic such as or of the stools is from for the first for and stools are a feature of massive stools are a feature of functional fecal retention. Abdominal distension, stool, failure to thrive, and lack of encopresis all a distal it is Hirschsprung disease, anal small colon, or infantile age and at onset of encopresis should be may be more erratic than Encopresis in the absence of constipation an or behavioral The response of the to the soiling also should be history of or rectal should be and the age of onset of constipation is older than or the is more to rectal fissures are usually a of external rectal fissures may be a of constipation initiated by or history such as and of that may to constipation should to a of or chronic or attention deficit hyperactivity disorder may to use of the on bowel intervals of significant diarrhea should about enterocolitis in infants or irritable bowel in the children who have encopresis evacuate loose stool for the to it the family to a to and history to the the frequency and of the stool and of pain or of the allows an of and as well as fiber of and some of the child that could be examination with of and in the or of to and the The of the examination should on features of and include a is for of distension and by the a that can be at to are and the is for of streptococcal or fissures, and anal The anal is and the to the and or anus is are very in with constipation. An anal may be seen with passage of manifestations of disease include abscess, or in to rectal rectal examination is performed with the child as as on the The anal canal, often tight on should relax in the absence of a aganglionic The normal ampulla is dilated and may stool. A dilated ampulla filled with retained firm stool is a feature of functional retention. fissures may be in all the presence of a pelvic mass or An rectal is of an abdominal examination may demonstrate palpable dilated of and distal colon. stool in the colon in the presence of an ampulla enema use or proximal from or enterocolitis The back should be for to lower is to some of the by of the history or physical examination. may include or and should be in all children who have a history of it is associated with abdominal may be of in the child in an abdominal examination is or to the of evacuation in a child who or can be to the As previously, the barium enema is an for the transition zone of aganglionic bowel. The barium enema may normal in the presence of colonic but the enterocolitis will be defined In normal children, the of the rectum that of the in Hirschsprung disease, the is The contrast enema has a in pelvic muscle surgery or in the context of central is to internal anal sphincter relaxation and the of pressure in older It also will the 25% of chronically constipated children who a increase in external anal sphincter pressure a feature that a to and a for A few colonic a valuable in the of or in chronic intestinal of the suction rectal biopsy has increased with the to the tissue for ganglion cells and acetylcholinesterase, the of which is and the of which is increased in Hirschsprung disease. The rectal biopsy also can be of diagnostic in the child who has disease, disease, or disease. are by the to document normal segments of colon at the time of for are three of complete evacuation or sustained evacuation to normal and from The of each on the and of the when the The in this are listed in Table are about normal patterns of evacuation, the physical and of the present the of and the of the for response to the of of the and the for The older child is to be involved by a or to document and of these older children have been toilet are to a of toilet use independent of the of simple but critical in management is to use a for the child to abdominal pressure the Valsalva modification are to the of evacuation, on the and to As previously, counseling of the child and family can be to the are two to the of the family is to reduce such as and fiber has no when tone is in the child who has functional fecal retention. In the second when tone is being fiber is of to of evacuation and usually is in the form of a is dietary fiber is and are increased to and are Table and for and Table a few of the and in management will complete evacuation is not after the passage of a massive stool that an colon. is but the is to rectal the rectal examination a of stool, will be for up to 2 to to and usually with a oil which is to the rectal mass and the It is followed in with a The usually are at in the until evacuation is 3 to is because of the for and should be avoided because of the of water and bowel If the child fails to evacuate with the use of oil and a enema can be contrast is by the is a of and but is at some the of a rectal and the of of with of rectal is with oil for 3 is not used in a child who has is not with or the child be to the for and with volumes of to per are most children require a children being for usually evacuate in 6 to 8 who chronically may not evacuate for more than are is no for of Some is and may be have no rectal distension so they are of in those older than 6 months of have in the constipated child who does not have but they are into the of the fecal mass and or reach the rectal evacuation has been the is to the rectum This is accomplished by toilet stool and laxatives to daily complete This can from 2 to 6 months or The is to allow the distended colon to to normal and When this is encopresis due to functional fecal retention can resolve within who have or behavioral encopresis should be in this The is a of behavioral and children who have failure of anal or imperforate anus are for therapy with an infancy, softening of the stool is usually As noted in Table this can be addressed with barley barley 4 to 6 or after 6 months of age, with lactulose. can be associated with increased for a few until evacuation cereal and should be a variety of are most infants can the nondigestible but may occur with the transition to and at 1 of are the most to early are fecal with and to behavior The parents also to they are of the for and of such training should not be until the physical and of the constipation are and laxatives are for months or stools usually are with or is at to increasing as up to is only by which often is a and stools occur oil is an for toddlers and older It is at 2 per dose and increased as up to 6 to 8 per oil may occur until the dose is about oil with of have not been in laxatives such as of and usually are are at 2 to reach a of one to three stools a day 1 to 2 weeks. children will the one to three daily and the dose to the with the of no to evacuate in increasing use of to has to of as a It is used in and with its use in the has been When in a dose of per dose with a of per has been reported in children who had constipation and It usually is to the laxative also has been is in children because therapy usually is and are concerns about the of regular evacuation has been the use of laxatives is are of or is other day in the dose for 1 then 3 for 1 month regular complete evacuation the of or fiber should be fiber are in part by fecal which to increased fecal are increased to and are as to in or the fiber can be in and into In contrast to stool fiber allows increased rectal distension and of the to may toilet training in some occur or a suppository should be on the day on which no stool is passed to prevent of colon and of the in the and as the child children are with the a greater of and a greater for behavioral modification can be is in the older child to the of regular toilet use is in the of of will be rates of of the for