Pediatric Functional Constipation

Etiology

Functional constipation is commonly seen in preschool children, especially during toilet training. Although specific individuals may be more prone to constipation than others, a common cycle of events or triggers often leads to functional constipation.[3]

• The most common event or trigger is painful or frightening defecation; a single event alone can precipitate functional constipation.                                                                                                                                       
• Age Differences:
  • Toddlers
    • Dietary changes (breastfed to formula or cow's milk) lead to dry, hard stools with anal fissures and pain.
    • Toilet training: Excessive parental pressure, anxiety, and the exertion of  the child's own will can lead to functional constipation
  • Older children
    • Unpleasant toilet facilities away from home
    • Sexual abuse
    • Trauma to the perianal area
    • Voluntary withholding while playing

Epidemiology

Functional constipation is a common childhood issue with varying prevalence across geographic regions. In Europe, the prevalence (including children) is estimated to be between 0.7% and 12%, while in North and South America, the prevalence (including infants and adolescents) is between 10% and 23%. Functional constipation prevalence varies from 0.5 to 29.6% in Asia.[4]

Pathophysiology

Holding stools rather than emptying the colon leads to stool accumulation.[5] The colon removes water from stool, making it harder and more challenging to pass. As stool accumulates, 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. 

History and Physical

Functional constipation is a clinical diagnosis based on history and physical examination. History should include information about the frequency and consistency of stools, associated issues, and the duration of symptoms. Parents often describe small and hard stools “like little pebbles,” while others describe infrequent, large bowel movements that are “so big I can’t believe it came out of him/her.” 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 abdominal examination. Past medical history should include questions about neurologic abnormalities, surgeries, and any chronic conditions like hypothyroidism, Hirschsprung disease, and cystic fibrosis that may contribute to difficulty passing stool. Social and developmental history may suggest concerns about lead intoxication.[6]

A thorough head-to-toe physical examination is necessary. General examination should include growth parameters and vitals. Exophthalmos, lid lag, and abnormalities on the thyroid exam may suggest hypothyroidism. The abdominal exam may reveal a palpable fecal mass, indicating fecal impaction. Look for Abdominal distention, which could indicate prune belly syndrome, an abdominal mass, or other significant abnormality should be noted. Significant pain with palpation of the abdomen may require an additional evaluation for appendicitis, ovarian torsion, or other acute abdominal processes.[2]

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 be evaluated to ensure it is patent and normally placed. A rectal exam, although not routinely indicated, may be helpful to confirm hard stool in the rectal vault, rule out presacral masses, and assess rectal tone. Abnormal strength, reflexes, sensation, or muscle mass of either or both lower extremities may be present.[2]

Evaluation

Rome IV defines functional constipation separately for infants and children older than 4 years of age.[7]

For Infants up to 4 Years

Must include 1 month of at least 2 of the following or 2 or fewer defecations per week

1. History of excessive stool retention
2. History of painful or hard bowel movements
3. History of large-diameter stools
4. Presence of a large fecal mass in the rectum

In toilet-trained children, the following additional criteria may be used:

1. At least 1 episode/week of incontinence after the acquisition of toileting skills
2. History of large-diameter stools that may obstruct the toilet

For Children Older than 4 Years

Must include 2 or more of the following occurring at least once per week for a minimum of 1 month with insufficient criteria for a diagnosis of irritable bowel syndrome:

1. Two or fewer defecations in the toilet per week in a child of a developmental age of at least 4 years
2. At least 1 episode of fecal incontinence per week
3. History of retentive posturing or excessive volitional stool retention
4. History of painful or hard bowel movements
5. Presence of a large fecal mass in the rectum
6. History of large-diameter stools that can obstruct the toilet

After appropriate evaluation, another medical condition cannot fully explain the symptoms.

Children with a history and exam consistent with functional constipation may not require any specific testing. Children who do not respond to treatment, have an atypical history, or raise clinician concerns on the 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 should always be considered, especially in young, persistent, or atypical cases. A contrast enema can help with the diagnosis, and referral for a possible biopsy is also an option that will more definitively exclude the diagnosis of Hirschsprung disease.[8] 

Imaging studies may be helpful to rule out other suspected disorders but are not required to diagnose functional constipation.[9][10][11][12] An abdominal X-ray abdomen can help diagnose fecal impaction, especially in a child where the abdominal examination is difficult, but it is not done routinely. 

Treatment / Management

Disimpaction

The first phase of treatment is to empty the hard stool from the colon, also known as disimpaction. Removing the impacted, hard stool allows the colon to return to normal size and function. In the past, manual removal, suppositories, and enemas were common methods during this phase of treatment. Some treatment options are glycerin enemas, saline enemas, milk of molasses enemas, and, recently, olive oil enemas.[13] 

In pediatric practice, however, in an outpatient setting, polyethylene glycol (PEG 3350) has become the first-line treatment for FC due to its efficacy and 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 g/kg to 1.5 g/kg of PEG 3350 mixed with 6 oz to 8 oz of water or juice. Significantly higher doses have been used, especially in the hospital setting. Patients should be encouraged to drink the preparation 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 2 days of treatment or significant abdominal discomfort, persistent vomiting, or other concerns, the family should follow up for reevaluation.[14](A1)

Maintenance Therapy

In the second phase of treatment, the goal is to keep the stool very soft, preventing reaccumulation of hard stool while the colon returns to normal size and function. Drugs in this phase are oral medications.[11]

1. Osmotic Laxatives
   • Polyethylene glycol (PEG) 3350 0.2 g/kg/d to 0.8 g/kg/d
   • Lactulose 1 mL/kg/d to 3 mL/kg/d
   • Magnesium hydroxide 0.5 mL/kg/d to 3 mL/kg/d                                                                            
2. Stool Softeners
   • Docusate sodium 5 mg/kg/d
   • Mineral oil (lubricant) 1 mL/kg/d to 3 mL/kg/d                                                                                        
3. Stimulant Laxative for Rescue Therapy in Addition or Alone (duration <30 d)
   1. Senna 2.5 mL/d to 7.5 mL/d
   2. Bisacodyl 5 mg/d to 10 mg/d

Nonpharmacological Interventions

Normal fiber and fluid intake are recommended for children with constipation, along with an average amount of physical activity. There is no evidence to support the routine use of intensive behavioral protocolized therapy programs or biofeedback in addition to conventional treatment. There is no evidence to suggest the efficacy of prebiotics or probiotics in treating constipation.[15]

Adequate fluid intake is essential, as is age-appropriate activity. Children who are toilet 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 routine will take advantage of the gastrocolic reflex and reduce the risk of constipation by "training" the child to have a daily bowel movement. A follow-up appointment should occur in 1 to 3 weeks to assess the treatment's efficacy and consider necessary changes in the plan of care.

Differential Diagnosis

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 like meningomyelocele and Hirsprung disease. Toxins like botulinum toxin (sometimes found in honey) and medications like opiates can also cause constipation. In older children, irritable bowel syndrome is also a consideration.[11]

Red Flags Concerning for an Organic Disorder

• Systemic symptoms such as fever, abdominal distention, weight loss or poor weight gain, decreased appetite, and bloody diarrhea
• Onset before 1 month of age
• Delayed passage of meconium
• Failure to thrive
• Intermittent diarrhea and explosive stools
• Abnormal neurological examination such as low tone, loss of cremasteric reflex, and decreased lower extremity reflexes.
• No response to treatment

In most cases, a thorough history and physical examination 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 younger than 1 year old, who are not growing well, or who do not respond to treatment often warrant additional testing. The physical exam should focus on the abdominal and lower extremity neurologic exams. 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 ensure it is normal in appearance and location. A rectal exam can be uncomfortable but can assess for rectal tone, the presence of hard stool in the vault, and a large presacral mass.

Growth curves should be reviewed, looking for signs of growth failure or changes in the growth curve.[10]

Pertinent Studies and Ongoing Trials

Lubiprostone is a locally acting ClC-2 chloride channel activator that increases fluid secretion into the intestines and helps improve constipation. It is approved for adults by the US Food and Drug Administration (FDA) but not for children yet.[16]

Prucalopride is a prokinetic agent that facilitates colonic motility and movement. This also improves bowel function and constipation-related symptoms but has only been tested in adults and is not recommended in children.[16]

Prognosis

The frequency of mandatory toilet visits and the use of laxatives can be reduced after the child develops regular bowel habits (and uses the toilet on their own). The laxative dose is gradually reduced to prevent fecal incontinence and maintain 1 to 2 daily bowel movements.[17]

Recurrent impaction and/or ongoing fecal incontinence suggest that treatment has failed and that education and other treatment components must be reviewed. Inadequate medication or premature withdrawal are the leading causes of treatment failures. Among patients referred to pediatric gastroenterologists, 50% will recover as defined by 3 or more bowel movements per week without fecal incontinence and be without laxatives after 6 to 12 months. Approximately 10% are well while taking laxatives, and 40% will still be symptomatic despite laxatives.[2]

Complications

Although it might be uncomfortable, functional constipation in children is typically not a serious condition. However, issues could arise if constipation remains untreated.

1. Anal fissures usually present with bleeding and pain from the tear in the skin around the perianal                                    
2. Rectal prolapse, which can occur when the rectum protrudes beyond the anus                                                           
3. Hemorrhoids
4. Encopresis which is when impacted feces accumulate in the colon and rectum and stool leaks out