Constipation in children and adolescents is defined as passing delayed or infrequent hard stools with pain and excessive straining.^1,2 The prevalence of constipation in children and adolescents is estimated to be as high as 30% worldwide.³ Constipation in children accounts for 3% of primary care physician visits and up to 25% of referrals to pediatric gastroenterologists.¹ Children with constipation incur three times the health care costs of children without constipation,⁴ and chronic constipation can have a negative effect on the child's quality of life.⁵

Normal Defecation Patterns

The number of daily bowel movements decreases as a child ages, averaging four stools per day for infants, two stools per day by two years of age, and one stool per day after four years of age.¹ Infants who are exclusively breastfed are exceptions to these patterns because there may normally be several days between bowel movements.⁶

Classification

Functional constipation, for which there is no organic cause, is the most common type of constipation in children and adolescents, accounting for 95% of cases.⁷ Only 5% of constipation cases in children and adolescents can be attributed to an underlying etiology such as Hirschsprung disease, cystic fibrosis, Down syndrome, anorectal malformations, neuromuscular disorders, spinal cord abnormalities, or celiac disease. Certain medications such as opiates, antacids, or anticholinergics can also cause constipation.⁷

Functional constipation is classified as a functional gastrointestinal disorder that cannot be explained by structural or biochemical findings.⁸ Other functional gastrointestinal disorders in children that may be associated with constipation are infant dyschezia and nonretentive fecal incontinence. Infant dyschezia occurs in infants younger than nine months who have constipation-like symptoms, including straining, crying, and transient reddening of the face, but frequently pass soft stools. These symptoms resolve on their own and are usually due to a discoordination of anal sphincter muscles.^2,7 Nonretentive fecal incontinence differs from functional constipation by the presence of fecal incontinence without stool impaction, a normal number of stools, and normal colonic transit time in children four to 18 years of age. Significant psychosocial problems or neurologic lesions may be found in children with nonretentive fecal incontinence.²

Encopresis is not mentioned in the Rome IV diagnostic criteria for constipation; however, it is included in the Diagnostic and Statistical Manual of Mental Disorders, 5th ed., as an elimination disorder that can occur with or without fecal retention. Encopresis is the repeated passage of feces in inappropriate places (i.e., clothing or floor), with one or more events occurring each month for three or more months, and the key feature is soiling.^2,6–10

Etiology and Pathophysiology

Constipation commonly starts with the transition to solid foods, toilet training, or school entry. The median age of onset of functional constipation is 2.3 years of age.^2,11 There is no difference in the prevalence of functional constipation between girls and boys.³

Constipation leads to painful bowel movements, which can cause the child to withhold stool. Withholding stool increases colonic water absorption, making the stool firmer and more difficult to pass. The child contracts the anal sphincter or gluteal muscles by stiffening the body to avoid another painful bowel movement. The child may hide in a corner, rock back and forth, or fidget with each urge to defecate. Parents often confuse these withholding behaviors as straining to defecate.¹² Over time, fecal retention stretches the rectum, which decreases the urge to defecate. The accumulation of stool in the rectum causes a decrease in gastric emptying, resulting in abdominal distention, abdominal pain, nausea, and loss of appetite.² Although children may have painful or traumatic defecation experiences, resulting in stool withholding, adolescents suppress the urge to defecate as a learned behavior.¹³