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 may have a sacral dimple and motor deficits of the lower extremities on physical examination. In general, patients with constipation secondary to an organic illness rather than functional constipation have some additional finding or red flag on the history or physical examination to warrant further investigation.

Figure 112-1 Megacolon (Hirschsprung’s disease).

Table 112-1 Distinguishing Functional Constipation from Hirschsprung’s Disease

	Functional Constipation	Hirschsprung’s Disease
Onset	Rare in infancy	Common in infancy
Delayed passage of meconium	Rare	Common
Encopresis	Common	Unusual
Stool size	Very large	Small, ribbonlike
Failure to thrive	Rare	Common
Abdominal distension	Variable	Common
Painful defecation	Common	Rare
Stool in rectal vault	Common	Rare
Anal tone	Open, distended	Tight

Adapted from Graham-Maar RC, Ludwig S, Markowtiz J: Constipation. In Fleisher, Ludwig (eds): Textbook of Pediatric Emergency Medicine, ed 5. Philadelphia, Lippincott, Williams & Wilkins, 2006 and Behrman RE, Kliegman RM: Nelson Essentials of Pediatrics, ed 4. St. Louis, Saunders, 2002.

History

A thorough history is important in discriminating between functional constipation and that caused by an organic illness. It is important to determine the timing of the child’s first bowel movement (i.e., how soon after birth did the baby first stool?), the onset of the constipation, the frequency and consistency of bowel movements, the presence or absence of blood in the stool, tenesmus (ineffectual straining with defecation), withholding behaviors, and encopresis. The history should probe for red flags such as fever, vomiting, bloody diarrhea, failure to thrive, weight loss, or signs or symptoms that are consistent with the disorders listed in the differential diagnosis above. It is also important to elicit a thorough dietary history because many children with constipation have inadequate fiber and fluid intake.

Physical Examination

The physical examination should include a thorough abdominal examination; external examination of the perianal region, including assessment of the anal wink reflex (contraction of the anus elicited by stroking the perianal area); and a digital rectal examination. Upon digital rectal examination, the size of the anal canal and rectum should be noted in addition to the presence or absence of stool and the consistency of the stool. It is recommended that a test for occult blood be performed in all infants with constipation and in any child who also has abdominal pain, failure to thrive, intermittent diarrhea, or a family history of colon cancer or colonic polyps.

Evaluation and Management

Because the majority of children with constipation have functional constipation, an extensive medical workup is often not necessary. If Hirschsprung’s disease is a concern, an unprepared barium enema to look for a transition zone and a rectal biopsy to detect ganglion cells are indicated. Other tests that might be indicated based on the history and physical examination findings may include thyroid function tests, celiac antibodies, a lead level, a calcium level, a sweat test, and magnetic resonance imaging or ultrasound of the lumbar spine.

If organic disease has been ruled out or deemed unlikely by the history and physical examination findings, no laboratory or radiologic investigation is absolutely necessary at the outset. The clinician might consider an abdominal plain radiograph to further illustrate the degree of fecal impaction or a Sitz marker study (a pill with radiopaque markers is swallowed and their progress through the gastrointestinal [GI] tract is tracked by radiography) after the patient is completely cleaned out to assess the patient’s colonic motility.

Treatment of functional constipation generally involves determining whether a fecal impaction is present, treating the impaction, initiating maintenance treatment with oral medication, and educating the patient and the family. Fecal impaction (Figure 112-2) is defined as a hard mass in the lower abdomen on physical examination, a dilated rectum filled with a large amount of hard stool on rectal examination or excessive stool on abdominal radiography. Disimpaction must occur before maintenance therapy can be effective and is best accomplished by the rectal route with phosphate enemas, saline enemas, or mineral oil enemas. An oral approach to disimpaction is slower and less effective than rectal disimpaction, but if necessary, it can be attempted with high doses of polyethylene glycol electrolyte solutions or with high-dose magnesium hydroxide, magnesium citrate, lactulose, sorbitol, senna, mineral oil, or bisacodyl.