Most individuals have bowel movements at regular intervals, and although the frequency varies from person to person, stools should pass without significant straining or discomfort. Functional constipation is a term used to describe a condition in which patients have hard, infrequent bowel movements that are often difficult or painful to pass. Functional constipation does not result from a clearly identifiable anatomic abnormality or disease process and is a diagnosis of exclusion. Factors including diet, fluid intake, activity level, bowel habits, and medications can contribute to constipation. This article discusses functional constipation in children 1 year of age and older. Constipation can occur at younger ages but may require a more thorough evaluation, different treatment, and closer follow up.
Although certain individuals may be more prone to constipation than others, a common cycle of events often leads to functional constipation. Holding stools rather than emptying the colon leads to stool accumulation. The colon removes water from stool, making it harder and more difficult to pass. As stool continues to accumulate, the smooth muscles in the intestinal walls are stretched and become less effective. The cycle of stool holding, removal of water from the stool, and stretching of the smooth muscles in the intestine, results in hard stools that are large and painful to pass, causing further stool holding. If this becomes a more chronic condition, a patient’s rectum fills with a hard stool on an ongoing basis, and they begin to lose the sensation of having to have a bowel movement. Soft stool often leaks around the harder “plug,” resulting in encopresis. Any regime intended to treat functional constipation must first empty the large, dry hard stool from the colon, then prevent re-accumulation of hard stool while the intestine returns to normal.
Functional constipation is a clinical diagnosis based on history and physical exam. History should include information about the frequency and consistency of stools, associated issues, and the duration of symptoms. Parents will often describe stools that are small and hard “like little pebbles,” while others describe infrequent, large bowel movements that are “so big I can’t believe it came out of him.” A history of bright red blood in the stool associated with large, hard bowel movements may indicate rectal fissures from passing hard bowel movements. A history of additional symptoms including weakness, abdominal pain, vomiting, and urinary symptoms can suggest organic causes for constipation. Lower extremity weakness should raise concerns of a neurologic cause. Abdominal pain, vomiting, enuresis, and encopresis can accompany functional constipation but should prompt additional questions and close attention to the examination of the abdomen. Past medical history should include questions about neurologic abnormalities, surgeries, and any chronic conditions like hypothyroidism, Hirschsprung disease or cystic fibrosis that may contribute to difficulty passing stool. Social and developmental history may suggest concerns about lead intoxication.
A thorough physical exam is absolutely necessary, looking for clues that suggest an organic cause for constipation. Exophthalmos, lid lag, and abnormalities on thyroid exam may suggest hypothyroidism. Abdominal distention could indicate prune belly syndrome, an abdominal mass, or other significant abnormality. Significant pain with palpation of the abdomen may require additional evaluation for appendicitis, ovarian torsion, or other acute abdominal processes. The back, especially the lumbar region, should be evaluated closely for midline defects, hair tufts, hemangiomas, dimples, or other abnormalities that could suggest underlying myelomeningocele. The anus should undergo an evaluation to assure it is patent and normally placed. A rectal exam may be helpful to confirm hard stool in the rectal vault, rule out presacral masses, and to assess rectal tone. Abnormal strength, reflexes, sensation or muscle mass of either or both lower extremity.
Children with history and exam consistent with functional constipation may not require any specific testing. Children who do not respond to treatment, who have an atypical history, or concerns on physical exam may require additional information or referral to a specialist. A TSH can screen for hypothyroidism, and a lead level can be helpful if lead intoxication is a concern. Hirschsprung disease is always a consideration, especially in very young, persistent or atypical cases. A contrast enema can help with the diagnosis, and referral for possible biopsy is also an option that will more definitively exclude the diagnosis of Hirschsprung's disease. Imaging studies may be helpful to rule out other suspected disorders but are not required to diagnose functional constipation.
The first phase of treatment is to empty the hard stool from the colon. Removal of impacted, hard stool allows the colon to begin returning to normal size and function. In the past, manual removal, suppositories, and enemas were common methods during this phase of treatment. Polyethylene glycol (PEG 3350) has become the first treatment of functional constipation due to its efficacy, safety profile and because it is well tolerated. There are variations in the amount of PEG 3350 recommended for the cleanout phase of the treatment regime, but a reasonable dose would be 1 to 1.5 grams per kilogram PEG 3350 mixed with 6 to 8 oz. water or juice. Significantly higher doses have been used, especially in the hospital setting. Patients should be encouraged to drink this over 3 hours if possible. If there has not been a significant response to this treatment, the patient can repeat the dose the next day. If there is no response after two days of treatment, or if there is significant abdominal discomfort, persistent vomiting or any other concerns, the family should present for follow up and re-evaluation.
In the second phase of treatment, the goal is to keep the stool very soft, preventing re-accumulation of hard stool while the colon returns to normal size and function. Healthy habits are also introduced to prevent recurrence. PEG 3350 is continued once daily for at least a week. In general, individuals who have had constipation for longer periods require a longer duration of treatment. A reasonable dose for the second phase of treatment is:
The medication should be mixed in 6 to 8 oz. of juice or water. Daily dosages can be adjusted if stool remains hard or becomes excessively loose. Parents should increase their child’s intake of dietary fiber by encouraging developmentally appropriate raw fruits and vegetables and bran. Adequate fluid intake is essential, as is age appropriate activity. Children who are potty trained should be encouraged to sit on the toilet and try to have a bowel movement for 5 to 10 minutes at the same time of day, every day, after the same meal; this will take advantage of the gastro-colic reflex and reduce the risk of constipation by “training” the child to have a bowel movement every day. A follow-up appointment should occur in 1 to 3 weeks to assess the efficacy of the treatment, as well as to consider necessary changes in the plan of care.
The differential diagnosis of constipation includes anatomic abnormalities like anal atresia and presacral masses, metabolic conditions like hypothyroidism, cystic fibrosis, and lead intoxication, and neurologic conditions including meningomyelocele and Hirsprung disease. Toxins like botulinum toxin (sometimes found in honey) and medications like opiates can cause constipation as well. In older children, irritable bowel syndrome is also a consideration.
In most cases, a thorough history and physical exam will rule out most of these conditions. A history of lower extremity weakness or loss of bladder continence raises concern for a neurologic cause. Children who are less than one-year-old, who are not growing well, or who do not respond to treatment often warrant additional testing. The physical exam should devote special attention to the abdominal exam and lower extremity neurologic exam. A spinal exam should look for signs of neural tube defects like hemangiomas and large dimples with hair tufts in the midline. The anus should be inspected to assure it is normal in appearance and location. A rectal exam can be uncomfortable but can assess rectal tone, the presence of hard stool in the vault, and presence of a large presacral mass. Growth curves should be reviewed looking for signs of growth failure or changes in the growth curve.
The criteria for diagnosing functional gastrointestinal disorders was recently updated (Rome IV Criteria)
Children with functional constipation often present with abdominal pain, which can be challenging to differentiate from appendicitis. A recent study suggests laxatives and/or enema may help identify children whose abdominal pain is caused by constipation when they return for a second medical visit with the complaint of abdominal pain.
Although PEG 3350 can be used alone to treat functional constipation, there are studies using alternative therapies including the combination of enema and peg 3350 in the initial phase of management.
Successful treatment of functional constipation requires a team approach. Family members, health care providers and the patient all have to play their part in the treatment of functional constipation and to prevent complications like encopresis and recurrent abdominal pain.
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