Constipation

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112 Constipation

Constipation is an extremely common complaint in children, accounting for 3% to 5% of all visits to general pediatric clinics and as many as 30% of visits to pediatric gastroenterologists. The North American Society of Gastroenterology and Nutrition defines constipation as “a delay or difficulty in defecation, present for 2 weeks or more, and sufficient to cause significant distress to the patient.” The majority of children meeting this definition do not have an underlying medical condition and are thus labeled as having functional constipation, which is the focus of this chapter.

Etiology and Pathogenesis

Functional constipation is usually caused by painful bowel movements, which then results in voluntary withholding of stool. This withholding then leads to prolonged fecal stasis in the colon, reabsorption of fluids, and increased size and hardened consistency of the stools. The fear of passing large, hard stools that may stretch the anus and cause pain leads to further withholding and avoidance of all defecation. Over time, the rectum gradually accommodates the enlarging fecal mass, the urge to defecate decreases, and this retentive behavior becomes automatic. Fecal soiling, or encopresis, can occur as the rectal wall stretches and causes loss of rectal sensitivity and the urge to defecate.

Clinical Presentation

The aforementioned North American Society of Gastroenterology and Nutrition definition is one of several definitions proposed for constipation. The Paris Consensus on Childhood Constipation Terminology defines it as “a period of 8 weeks with at least 2 of the following symptoms: defecation frequency less than 3 times per week, fecal incontinence frequency greater than once per week, passage of stools so large that they obstruct the toilet, palpable abdominal or rectal fecal mass, stool withholding behavior, or painful defecation.” The Rome III criteria include separate definitions for infants and toddlers and for children ages 4 to 18 years. Constipation in infants and toddlers is defined as at least two of the following for at least 1 month: two or fewer defecations per week, at least one episode of incontinence after the acquisition of toileting skills, history of excessive stool retention, history of painful or hard bowel movements, the presence of a large fecal mass in the rectum, or a history of large-diameter stools that may obstruct the toilet. In children ages 4 to 18 years of age, constipation is defined as at least two of the following present for at least 2 months: two or fewer defecations per week, at least one episode of fecal incontinence per week, a history of retentive posturing or excessive volitional stool retention, a history of painful or hard bowel movements, the presence of a large fecal mass in the rectum, or a history of large-diameter stools that may obstruct the toilet.

Children with functional constipation can present with decreased stooling; decreased oral intake; and abdominal pain, distension, or cramping. They may also report painful, hard bowel movements, and the parents may report withholding behaviors. Encopresis may also develop if the constipation is severe. Functional constipation often develops around the time of weaning or dietary transition in infants, toilet training in toddlers, or school entry in older children. The physical examination may reveal palpable stool in the abdomen, as well as an enlarged rectum with palpable stool just beyond the anal verge.

Differential Diagnosis

Although the majority of children with constipation have functional disease, it is important to consider the broad differential diagnosis of constipation in the pediatric population (Box 112-1). Patients with an organic disease usually present with a range of symptoms or physical findings in addition to constipation. Children with Hirschsprung’s disease (Figure 112-1) often do not pass meconium during the first 36 hours of life and have problems with constipation beginning in infancy (Table 112-1). On examination, the rectum is generally very small and empty of stool. Patients with constipation secondary to hypothyroidism generally have other symptoms and findings, including lethargy, hypotonia, a large fontanelle if presenting in infancy, short stature, cold intolerance, dry skin, feeding problems, and a palpable goiter (see Chapter 68). Celiac disease can also present with constipation in addition to poor growth and abdominal pain. Children with lead poisoning can present with constipation in addition to vomiting and intermittent abdominal pain. Patients with a tethered spinal cord

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