Constipation in Children

Organic causes of constipation involve specific structural, neurologic, toxic/metabolic, or intestinal disorders. They are rare but important to recognize ( see Table: Organic Causes of Constipation in Infants and Children).

The most common organic cause is

• Hirschsprung disease

Other organic causes that may manifest in the neonatal period or later include

• Anorectal malformations

• Cystic fibrosis

• Metabolic disorders (eg, hypothyroidism, hypercalcemia, hyperkalemia)

• Spinal cord abnormalities

Functional constipation is difficulty passing stools for reasons other than organic causes.

Children are prone to develop functional constipation during 3 periods:

• After the introduction of cereals and solid food

• During toilet training

• During the start of school

Each of these milestones has the potential to convert defecation into an unpleasant experience.

Children may put off having bowel movements because the stools are hard and uncomfortable to pass or because they do not want to interrupt play. To avoid having a bowel movement, children may tighten the external sphincter muscles, pushing the stool higher in the rectal vault. If this behavior is repeated, the rectum stretches to accommodate the retained stool. The urge to defecate is then decreased, and the stool becomes harder, leading to a vicious circle of painful defecation and worsened constipation. Occasionally, soft stool passes around the impacted stool and leads to stool incontinence (encopresis).

In older children, diets low in fiber and high in dairy may lead to hard stools that are uncomfortable to pass and can cause anal fissures. Anal fissures cause pain with stool passage, leading to a similar vicious circle of delayed bowel movements, resulting in harder stool that is more painful to pass.

Stress, desire for control, and sexual abuse are also some of the functional causes of stool retention and subsequent constipation.

History of present illness in neonates should determine whether meconium has been passed at all and, if so, when. For older infants and children, history should note onset and duration of constipation, frequency and consistency of stools, and timing of symptoms—whether they began after a specific event, such as introduction of certain foods or a stressor that could lead to stool retention (eg, introduction of toilet training). Important associated symptoms include soiling (stool incontinence), discomfort during defecation, and blood on or in the stool. The composition of the diet, especially the amount of fluids and fiber, should be noted.

Review of systems should ask about symptoms that suggest an organic cause, including new onset of poor suck, hypotonia, and ingestion of honey before age 12 months (infantile botulism); cold intolerance, dry skin, fatigue, hypotonia, prolonged neonatal hyperbilirubinemia, urinary frequency, and excessive thirst (endocrinopathies); change in gait, pain or weakness in lower extremities, and urinary incontinence (spinal cord defects); night sweats, fever, and weight loss (cancer); and vomiting, abdominal pain, poor growth, and intermittent diarrhea (intestinal disorders).

Past medical history should ask about known disorders that can cause constipation, including cystic fibrosis and celiac disease. Exposure to constipating drugs or lead paint dust should be noted. Clinicians should ask about delayed passage of meconium within the first 24 to 48 hours of life, as well as previous episodes of constipation and family history of constipation.

The physical examination begins with general assessment of the child’s level of comfort or distress and overall appearance (including skin and hair condition). Height and weight should be measured and plotted on growth charts.

Examination should focus on the abdomen and anus and on the neurologic examination.

The abdomen is inspected for distention, auscultated for bowel sounds, and palpated for masses and tenderness. The anus is inspected for a fissure (taking care not to spread the buttocks so forcefully as to cause one). A digital rectal examination is done gently to check stool consistency and to obtain a sample for occult blood testing. Rectal examination should note the tightness of the rectal opening and presence or absence of stool in the rectal vault. Examination includes placement of the anus and presence of any hair tuft or pit superior to the sacrum.

In infants, neurologic examination focuses on tone and muscle strength. In older children, the focus is on gait, deep tendon reflexes, and signs of weakness in the lower extremities.

The following findings are of particular concern:

• Delayed passage of meconium (> 24 to 48 hours after birth)

• Hypotonia and poor suck (suggesting infant botulism)

• Abnormal gait and deep tendon reflexes (suggesting spinal cord involvement)

A primary finding that suggests an organic cause in neonates is constipation from birth; those who have had a normal bowel movement are unlikely to have a significant structural disorder.

In older children, clues to an organic cause include constitutional symptoms (particularly weight loss, fever, or vomiting), poor growth (decreasing percentile on growth charts), an overall ill appearance, and any focal abnormalities detected during examination ( see Table: Organic Causes of Constipation in Infants and Children). A well-appearing child who has no other complaints besides constipation, who is not taking any constipating drugs, and who has a normal examination likely has a functional disorder.

A distended rectum filled with stool or the presence of an anal fissure is consistent with functional constipation in an otherwise normal child. Constipation that began after starting a constipating drug or that coincides with a dietary change can be attributed to that drug or food. Foods that are known to be constipating include dairy (eg, milk, cheese, yogurt) and starches and processed foods that do not contain fiber. However, if constipation complaints begin after ingestion of wheat, celiac disease should be considered. History of a new stress (eg, a new sibling) or other potential causes of stool retention behavior, with normal physical findings, support a functional etiology.

For patients whose histories are consistent with functional constipation, no tests are needed unless there is no response to conventional treatment of constipation. An abdominal x-ray should be done if patients have been unresponsive to treatment or an organic cause is suspected. Tests for organic causes should be done based on the history and physical examination ( see Table: Organic Causes of Constipation in Infants and Children):

• Barium enema, rectal manometry, and biopsy (Hirschsprung disease)

• Plain x-rays of lumbosacral spine; MRI considered (tethered spinal cord or tumor)

• Thyroid-stimulating hormone and thyroxine (hypothyroidism)

• Blood lead level (lead poisoning)

• Stool for botulinum toxin (infant botulism)

• Sweat test and genetic testing (cystic fibrosis)

• Calcium and other electrolytes (metabolic derangement)

• Serologic screening usually for IgA antibodies to tissue transglutaminase (celiac disease)