Anal canal axis Pubis Anorectal angle Rectal axis
Puborectal muscle Anal verge
External anal sphincter Internal anal sphincter
Rectum
prevalence of fecal incontinence was approximately 4.4%
in these patients.5 Constipation accounts for up to 25% of visits to pediatric gastroenterologists, and therefore causes a signifi cant fi nancial burden on the health care system.
Children with constipation use more health care services amounting to a cost of an additional $3.9 billion/year as compared to children without constipation.6
The incidence of functional constipation appears to be rising over the last few decades. The reason for this increase is not well known, but may be due to changing patterns in toilet training, diminished dietary fi ber intake, lack of exercise, or better access to health care services and improved diagnosis. Socioeconomic fac- tors, such as lower income and family education, put children at risk for developing constipation. Another factor that appears to play a role in functional constipa- tion is diet. A low-fi ber diet and obesity are associated with an increased risk of functional constipation.7
PATHOGENESIS
It is important to explain the physiology of defecation and the pathogenesis of withholding and incontinence to parents. Figure 5–1 shows the anatomy of the
anorectal region. The anorectal angle is formed by the internal and external anal sphincters with the puborec- talis muscle. The angle is approximately 85–105° at rest.
Normally, entry of stool into the rectum leads to relax- ation of the internal anal sphincter. This is known as the rectoanal inhibitory refl ex, and is an involuntary mechanism. The stool then passes into the anal canal, creating an urge to defecate which can be voluntarily suppressed until completed in a socially acceptable set- ting. Defecation begins with a voluntary increase in the intra-abdominal pressure and relaxation of the pub- orectalis and the levator ani muscles, straightening of the anorectal angle, allowing passage of the bowel movement through the voluntarily relaxed external anal sphincter.
Functional constipation is usually triggered by an experience of painful defecation. This pain leads to avoid- ance of defecation and voluntary stool-withholding behavior. Contraction of the pelvic muscles can prevent a bowel movement by pushing the stool proximally. The rectum can eventually accommodate this increasing stool mass. The colon absorbs fl uid from the retained feces, causing dry and hard stools. Furthermore, these dry, hard stools may cause anal fi ssures or tears resulting in more pain during defecation. This vicious cycle continues to result in long-standing functional constipation. With time, the retained fecal mass leads to rectal distention and loss of the ability to voluntarily contract the external anal sphincter. Eventually, rectal distention also leads to decreased rectal sensation and therefore a decreased urge to defecate. Liquid stools from the proximal colon seep around this mass to cause fecal incontinence.
Constipation can begin at any time, although children are most vulnerable during certain develop- mental stages. Infants who are being weaned from breast milk to cereals and solids are at risk for developing constipation. Most commonly children who are being
FIGURE 5–1 ■ Anatomy of the anorectal region.
Diagnosis of Functional Constipation by Rome III criteria2,3
Older children/adolescents (>4 years of age) Must include 2 months of two or more of the following
occurring at least once per week:
■ Two or fewer stools in the toilet per week
■ At least one episode of fecal incontinence per week
■ History of retentive posturing or excessive volitional stool retention
■ History of painful or hard bowel movements
■ Presence of a large fecal mass in the rectum
■ History of large-diameter stools that may obstruct the toilet
Infants/toddlers (<4 years of age)
Must include 1 month of at least two of the following:
■ Two or fewer defecations per week
■ At least one episode per week of incontinence after the acquisition of toilet skills
■ History of excessive stool retention
■ History of painful or hard bowel movements
■ Presence of a large fecal mass in the rectum
■ History of large-diameter stools that may obstruct the toilet
Accompanying symptoms may include irritability, decreased appetite, and/or early satiety. The accompanying symp- toms disappear immediately following passage of a large stool
Table 5–1.
pressured into toilet training are likely to develop constipation. The American Academy of Pediatrics therefore strongly recommends that parents avoid forc- ing their child into toilet training.8 Toilet training should be initiated only when the child shows interest. Older children may avoid bathrooms at school due to unhy- gienic conditions, lack of privacy, or even bullying, which puts them at risk for constipation.
CLINICAL PRESENTATION
A thorough history and examination are recommended in the evaluation of functional constipation. The fi rst step is to fi nd out what the family means when using the term constipation. The history should therefore include the frequency, size, and consistency of the stools. A com- mon presenting symptom in children with functional constipation is abdominal pain. In one study, chronic constipation was found to be the most frequent cause of acute abdominal pain.9 Toddlers may withhold stool and demonstrate typical posturing in the form of stiff- ening of the body and clenching of the buttocks. Chil- dren may assume a variety of positions and make bizarre movements while struggling to retain the bowel move- ment (Figure 5–2). The physician should determine the presence and frequency of fecal soiling. It is important to be aware that parents of children with fecal inconti- nence might seek medical attention for what they think is diarrhea. Table 5–2 shows common gastrointestinal symptoms and signs of functional constipation.
Children with constipation may also present with extraintestinal manifestations. Urinary tract symptoms
may include frequency, enuresis, and infections. The prevalence of urinary incontinence is also higher in children with constipation.5 When constipation causes fecal incontinence, depression and low self-esteem are common, and therefore obtaining a psychosocial and behavioral history is crucial. These children often have lower health-related quality of life scores due to lower emotional and social functioning.10
The history obtained should review the previous use of laxatives and the results of these treatments. The physician should inquire about intake of dairy products,
FIGURE 5–2 ■ (a and b) Common positions a child may take while struggling to retain bowel movement.
Symptoms and Signs of Functional Constipation Symptoms
Infrequent bowel movements Painful bowel movements Hard stools
Abdominal pain Fecal soiling Blood in stools Retentive posturing Signs
Abdominal distention Abdominal tenderness Abdominal fecal mass Anal fi ssure
Rectal fecal mass
Table 5–2.
a b
refl exes is also important to rule out any spinal cord lesions.
It is especially important to look for the presence of any symptoms or signs that might suggest an organic etiology. A referral to a specialist should be considered if the child has any of the ‘red fl ag’ clinical features shown in Box 5–1. In most cases, a referral should be made to a pediatric gastroenterologist when the con- ventional treatment fails or when there are features suggestive of Hirschsprung’s disease. Sometimes a refer- ral to a neurologist or a psychiatrist may be necessary if there are neurological or behavioral problems.
DIFFERENTIAL DIAGNOSIS
The diagnosis of functional constipation is usually straightforward. Almost 95% of childhood constipation is functional in nature. The remaining 5% can be attrib- uted to wide variety of conditions, as shown in Table 5–3.
Many of these etiologies are obvious by history and