Constipation is a common problem in childhood and is one of the most frequent reasons for a referral to pediatricians. It is termed functional or idiopathic in the absence of any organic etiology. Almost 95% of childhood constipation is functional in nature and only a small minority is due to an identifiable etiology. The diagnosis of functional constipation can usually be made with a detailed history and physical examination. Constipation can often be a chronic problem in children lasting for several months to years. Almost 50% of the patients presenting with constipation during childhood can remain constipated on long-term follow-up. Long-standing constipation and withholding often result into fecal incontinence. Constipation and incontinence can lead to low self-esteem and behavior problems, causing significant stress and anxiety to the patient and the parents. The therapeutic approach involves patient education, disimpaction, laxative therapy, and behavioral modification. The treatment typically lasts for months to years and relapses are common. A successful treatment outcome requires a team approach involving the patient, family, nurses, pediatricians, and the specialists. In this chapter, we will review the diagnostic evaluation and therapeutic approach to functional constipation.

The term constipation is often defined differently by different parents. Constipation may mean infrequent bowel movements, hard stool consistency, large stool size, painful defecation, or voluntary withholding bowel movements. To most parents, constipation usually means infrequent bowel movements. It is important to remember that stool frequency varies in children with age.1 Normally, the initial bowel movement is within the first 24 hours of birth. Delayed passage of stool should raise the suspicion for Hirschsprung’s disease. Infants have approximately four stools per day during the first week of life. The frequency also differs between breast-fed and formula-fed infants. Some normal breast-fed infants can have only one stool per week. The stool frequency gradually changes to one to two stools per day by the age of 4 years. An adult defecation pattern is achieved after 4 years of age. The decrease in stool frequency is associated with an increase in stool size and prolonged gastrointestinal transit. The majority of children are toilet trained by 4 years of age. Girls tend to achieve toilet training slightly earlier than boys. Encopresis or fecal incontinence is defined as involuntary passage of stools after the developmental age of 4 years.

The North American Society for Pediatric Gastroenterology and Nutrition (NASPGHAN) defines constipation as a delay or difficulty in defecation, present for 2 or more weeks and sufficient to cause significant distress to the patient.1

The 2006 Rome III criteria for childhood functional gastrointestinal disorders describe the diagnostic criteria of functional constipation for neonate/toddler and for child/adolescent age groups as shown in Table 5–1.2,3

Constipation is a common problem in children. The worldwide prevalence of childhood constipation in the general population ranges from 0.7% to 29.6%.4 In a study done in Iowa, the prevalence was found to be as high as 23% in the pediatric primary care clinics. The 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 significant financial 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 fiber intake, lack of exercise, or better access to health care services and improved diagnosis. Socioeconomic factors, such as lower income and family education, put children at risk for developing constipation. Another factor that appears to play a role in functional constipation is diet. A low-fiber diet and obesity are associated with an increased risk of functional constipation.7

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 puborectalis muscle. The angle is approximately 85–105˚ at rest. Normally, entry of stool into the rectum leads to relaxation of the internal anal sphincter. This is known as the rectoanal inhibitory reflex, 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 setting. Defecation begins with a voluntary increase in the intra-abdominal pressure and relaxation of the puborectalis 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 avoidance 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 fluid from the retained feces, causing dry and hard stools. Furthermore, these dry, hard stools may cause anal fissures 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 developmental 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 pressured into toilet training are likely to develop constipation. The American Academy of Pediatrics therefore strongly recommends that parents avoid forcing 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 unhygienic conditions, lack of privacy, or even bullying, which puts them at risk for constipation.

A thorough history and examination are recommended in the evaluation of functional constipation. The first step is to find out what the family means when using the term constipation. The history should therefore include the frequency, size, and consistency of the stools. A common 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 stiffening of the body and clenching of the buttocks. Children may assume a variety of positions and make bizarre movements while struggling to retain the bowel movement (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 incontinence 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, such as cheese, which can predispose to constipation. The child should be asked whether he avoids using bathrooms at school. A family history of conditions such as celiac disease or thyroid disorders should raise the suspicion of organic causes of constipation. The physician should inquire about the family structure and dynamics as the family support is an important factor in the overall successful outcome of the patient.

Examination

A careful examination of all systems should be performed in a child who presents with constipation. Particular attention should be paid to the height and weight of the child. Poor growth may suggest the presence of organic conditions such as hypothyroidism or celiac disease. An abdominal exam should be performed to look for tenderness, distention, or mass. A rectal examination is recommended at the initial visit. It is helpful to explain the procedure to the child to decrease his anxiety. Rectal examination should be avoided in case of an uncooperative child, presence of neutropenia, or sexual abuse. A rectal examination might be difficult in certain circumstances such as with obese children. The perianal area should be first examined for presence of fecal soiling, anal fissures, position of the anus, and perianal sensation. Digital rectal examination can assess the presence, size, and consistency of stools in the rectum, the anal canal tone, and the size of the rectal vault. An empty rectal vault with explosive passage of stool on rectal exam is strongly suggestive of Hirschsprung’s disease. The stool should be examined for presence of occult blood by guaiac testing. The lumbosacral spine should be examined for the presence of a sacral dimple or tuft of hair. An examination of the tone, strength, and reflexes 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 flag’ clinical features shown in Box 5–1. In most cases, a referral should be made to a pediatric gastroenterologist when the conventional treatment fails or when there are features suggestive of Hirschsprung’s disease. Sometimes a referral to a neurologist or a psychiatrist may be necessary if there are neurological or behavioral problems.