Functional Constipation and Fecal Incontinence

Normal Stooling Pattern

Stool frequency changes in children with age. The stool frequency gradually declines from more than four stools per day during the first week of life to one to two stools per day by the age of 4 years. Differences in stooling frequency have been observed between healthy breast-fed and formula-fed infants. In the first 3 months of life, breast-fed infants have more frequent, softer, and more yellow-colored stools than standard formula-fed infants. The type of feeding does not influence the stooling quantity. From 5 years of age, the majority of children pass stools daily or every other day without straining or withholding.

Constipation

For many years, physicians, patients, and parents have used different definitions for constipation. The Rome II criteria, developed in 1999, attempted to provide a symptom-based definition of functional constipation, mostly based on expert opinion. Such criteria were subsequently found to be too restrictive and were revised, between 2004 and 2006, in the Rome III version of pediatric functional gastrointestinal disorders. Burgers et al. retrospectively evaluated patients referred for functional defecation disorders, comparing the Rome II and Rome III criteria. They demonstrated that by using the Rome III criteria, functional constipation is diagnosed more frequently compared with the Rome II criteria (87% and 34%, respectively). In 2016, the Rome IV criteria were published, differentiating between children who are and are not toilet trained. To fulfill the new Rome IV criteria for functional constipation, children should have two or more of the symptoms described in Box 11.1 . Children that are not yet toilet trained do not need to fulfill the criteria of fecal incontinence and stools that obstruct the toilet. Also, the duration of symptoms in children has been changed from 2 months to 1 month.

Fecal Incontinence

Fecal incontinence is defined as the involuntary loss of stool into the underwear in a child older than the age of 4 years after the acquisition of toilet training skills. It represents an upsetting and psychologically distressing problem in children, affecting quality of life. ^, Functional fecal incontinence can be divided into constipation-associated fecal incontinence, or “overflow” incontinence, and FNRFI. More than 80% of the children with functional fecal incontinence have constipation-associated fecal incontinence. These findings were also observed in a Sri Lankan epidemiologic survey showing that indeed, constipation-associated fecal incontinence is 4.5 times more common than FNRFI.

Functional fecal incontinence in children can also be subclassified as either primary, in those children who have never been toilet trained, and secondary, in those in which the incontinence returns after successful toilet training.

It is important to differentiate between constipation-associated fecal incontinence and nonretentive fecal incontinence because these two conditions differ in etiology and management. The diagnostic criteria for FNRFI according to the Rome IV criteria are listed in Box 11.2 .

Constipation

Constipation is a common symptom in children, accounting for 3% to 10% of general pediatric outpatient visits and up to 25% of visits to pediatric gastroenterologists worldwide. The lack of consensus in diagnostic criteria and differences in cultural views about normal bowel habits may have contributed to the worldwide variation of the prevalence in the literature. Recently, a systematic review was published, reporting a worldwide prevalence of functional constipation according to the Rome criteria of 9.5%. The prevalence of constipation was described to be associated with geographic location. Studies in South America reported a prevalence of constipation ranging from 8.9% to 22.1%, ^, while studies conducted in Asia reported a lower prevalence of constipation, with a pooled prevalence of 6.3%. Conflicting results have been reported with respect to the age distribution of constipation. In a recent systematic review, no significant difference in prevalence of constipation was found in children younger and older than 4 years of age. A cross-sectional study by van Tilburg et al. reported a difference in prevalence of constipation between infants and toddlers (4.7% vs. 9.4%, respectively).

Fecal Incontinence

The worldwide prevalence of fecal incontinence is estimated between 0.8% and 7.8%. A 4% prevalence rate for functional fecal incontinence was found in a retrospective review in 482 children, 4 to 17 years of age, attending a primary care clinic in the United States. In this study, fecal incontinence was related to constipation in 95% of the children. Similarly, studies from Asia report prevalence data in Iran, South Korea, and Sri Lanka, ranging from 2.6% to 7.8%. ^{, ,}

Fecal incontinence is more common in boys, with a male-to-female ratio ranging from 3:1 to 6:1. There is a negative correlation between the prevalence of functional incontinence and age. It is more common in younger children (prevalence 4.1% in children ranging from 5 to 6 years of age and 1.6% in 11- to 12-year-olds). Similarly, a Sri Lankan study including children aged 10 to 16 years reported a lower prevalence (<1%) in children aged 16 years compared to children aged 10 years (5.4%). The majority of children with functional fecal incontinence seek medical care at the age of 7 to 8 years.

In contrast to constipation-associated fecal incontinence, FNRFI is rare and affects approximately 0.4% (range 0% to 1.8%) of children.

Constipation

The pathophysiology of constipation in children is thought to be multifactorial. In a fraction of patients, constipation is secondary to a known organic disorder. In more than 90% of children presenting with constipation, no obvious organic cause is found and thus it is classified as functional.

Constipation may occur at any age, but children appear most vulnerable in one of three phases: (1) infancy, with the introduction of cereals and other solids and weaning of (breast) milk; (2) toddlers, at the time of toilet training; and (3) older children who avoid bathrooms at school.

Constipation in the newborn and in early infancy is a special situation because of the possibility of a congenital disorder. If meconium passage is delayed for more than 24 hours, several diseases need to be considered, including Hirschsprung disease (HD) and anatomic defects of the spinal cord or anorectal malformations. A meconium plug may cause neonatal constipation and may be associated with either HD or cystic fibrosis. Table 11.1 depicts the organic causes of constipation.

In most children, constipation results from purposeful or subconscious stool withholding after the passage of a hard, painful, or frightening bowel movement. Fear of defecation leads to withholding of stool, called retentive posturing. Instead of relaxing the pelvic floor for defecation, the retentive infant will contract the pelvic floor and gluteal muscles in an attempt to avoid defecation. Children often stiffen their legs, grunt, or rise on their toes and rock back and forth. In many cases, this behavior is misinterpreted by parents as an extreme effort to pass stool. Loening-Baucke reports that 45% of constipated infants and toddlers exhibited stool-withholding behavior. A child may also refuse defecation as part of a control and independence struggle with parents during toilet training. A significant number of school-aged children refuse to use school toilets, often citing poorly maintained and unhygienic facilities. As a consequence of withholding, whatever the cause is, the rectal mucosa absorbs water from the fecal mass, and the retained stools become progressively more difficult to evacuate. This process leads to a vicious cycle of stool retention. When stool retention remains untreated for a long period, the rectal wall becomes stretched and a megarectum develops. This can result in overflow fecal incontinence, loss of rectal sensation and, ultimately, loss of normal urge to defecate.

Young infants with constipation should be differentiated from those with infant dyschezia. Infant dyschezia, according to the Rome IV criteria, is defined as straining and crying for at least 10 minutes before successful or unsuccessful passage of soft stools without any other health problem, in an infant younger than 9 months of age. Infant dyschezia differs from constipation in that the stools are not hard when passed. A Dutch study showed that the prevalence of infant dyschezia, according to the Rome III criteria, at 1 and 3 months of age is low (3.9% and 0.9%, respectively) and declines with age. Only 6.6% of infants with dyschezia developed constipation. In the new Rome IV criteria, the age limit has been changed from 6 months to 9 months because this Dutch study showed that 0.9% of the 9-month-old infants also fulfilled the criteria for infant dyschezia. Symptoms of infant dyschezia improve and resolve without intervention in most cases. Parents need to be reassured that this phenomenon is part of the child’s learning process and that interventions, like suppositories and laxatives, are unnecessary. No association has been found between development of early constipation and the timing, style, or techniques used for toilet training.

Little consensus exists in the pediatric literature regarding risk factors for childhood constipation, although genetic predisposition, nutritional factors (low consumption of fiber, fruit, and vegetables; cow’s milk protein [CMP] allergy), physical inactivity, and low socioeconomic and educational levels have been suggested to contribute to the development of childhood constipation. ^, Although several studies have revealed the possible association between obesity and constipation, a recent systematic review could not confirm this hypothesis due to large heterogeneity of studies. One possible hypothesis on the pathogenesis of obesity and constipation is alteration in the gut microbiota. To support this, one study showed that intestinal microbiota species, such as Bacteroides fragilis , Parabacteroides , and Alistipes finegoldii , in children with functional constipation differed from healthy controls, suggesting a possible role for microbial disturbances in the development of constipation. Future research needs to evaluate the exact role of these microbial disturbances and investigate this potential target for therapeutic interventions.

Furthermore, colonic manometry studies in children have revealed possible pathological mechanisms underlying functional constipation by identifying patterns of colonic motility dysfunction in children with chronic constipation.

Psychological factors, such as stressful life events, being bullied at school, sexual and physical abuse, and in particular anxiety and depression, are considered predisposing to constipation. In addition, constipation has been reported more frequently in children with specific behavioral phenotypes, such as autism spectrum disorders. Studies also have shown that children with attention-deficit/hyperactivity disorder (ADHD) have an increased prevalence of constipation and fecal incontinence as compared to healthy children. ^,

The coexistence of psychological factors and constipation is largely explained by the role of the brain–gut axis that plays an important role in the regulation of digestive processes. Through this brain–gut interaction, sensations arising from the gastrointestinal tract are transported from the enteric nervous system to the central nervous system and brain. Psychological and stress-mediated factors also can modulate colonic and rectal functions along this same axis. To support this, a recent study using functional magnetic resonance imaging (MRI) showed that patients with functional constipation had different patterns of brain processing of rectal distention as compared to healthy controls.

Fecal Incontinence

Functional fecal incontinence is caused by either retentive (constipation-associated) incontinence or FNRFI. Other causes of fecal incontinence are listed in Table 11.2 .

In otherwise healthy children, fecal incontinence is secondary to “overflow” and therefore results from the presence of constipation. Stool withholding creates a vicious cycle of progressive accumulation of feces and hardening of the fecal mass. Finally, feces seep between the fecal mass and rectal wall and escape through the anal canal when the sphincter muscles are relaxed. The volume of stool that leaks out is small and most of the time just stains the underwear. Incontinence of feces can occur both during the day and at night. Nocturnal incontinence is considered to be an indicator of severe accumulation of feces in the rectum.

On the other hand, children with FNRFI pass stools in inappropriate places without evidence of stool retention. The majority of them have complete evacuation of bowel, not just staining of the underwear as in retentive incontinence. The pathophysiology of FNRFI is still unclear. In patients with FNRFI, in contrast to children with constipation, colonic transit times (CTTs), rectal compliance, and sensitivity thresholds (as measured by rectal barostat) were normal. Moreover, adolescents with FNRFI showed different patterns of brain activation on functional MRI as compared to children with constipation during rectal distention.

Fecal incontinence is a stressful symptom for both patients and their families. ^, Parents may believe that the child can be blamed for fecal incontinence and should therefore be punished for accidents. Parental misconceptions about the causes of fecal incontinence could lead to a treatment delay. Furthermore, parental rearing styles, such as high autonomy and overprotection, have been found to be associated with a higher frequency of fecal incontinence in children. A study assessing parental knowledge about fecal incontinence demonstrated that seeking professional medical care could decrease parental misconceptions and increase understanding and helping of the child.

Risk factors for functional fecal incontinence are low socioeconomic background, unhygienic toilets, living in an urban area or war-affected zone, hospitalization of the child for another illness, and bullying at school. Psychological and behavioral abnormalities such as aggressive behavior, social withdrawal, anxiety, depression, disruptive and oppositional behavior, and poor school and social performances were frequently noted in children with functional fecal incontinence. Moreover, study by Joinson et al. showed that certain psychological factors at young age, such as difficult temperament and behavioral problems, were associated with the development of constipation-related fecal incontinence.

History

The medical history should include questions about the time of the first bowel movement after birth. It is well known that more than 99% of term newborns pass meconium in the first 48 hours of life. Because maturation of the intestinal motor function is delayed in preterm infants, they consequently may have a delay in the passage of the first stool. In addition, failure to pass the meconium within the first 24 hours of life raises the suspicion for HD or cystic fibrosis.

Other important questions include the age of onset; frequency, consistency, and size of stools; whether the child experiences pain during defecation or exhibits retentive posturing; and whether blood is present on the toilet paper. Hard-caliber stools, which may be large enough to clog the toilet, may cause anal fissures, commonly manifested as blood on the toilet paper. Information about the incontinence frequency and day and/or nighttime soiling must be obtained. Fecal incontinence can be mistaken for diarrhea by some parents. An assessment of the stool pattern using a defecation diary in combination with the Amsterdam Infant Stool Scale (AISS; Fig. 11.1 ), Brussels Infant and Toddler Stool Scale (BITSS), or Bristol stool scale (BSS) can be used to estimate the severity of constipation. The AISS and BITSS are developed for use in infants and children who are not yet toilet trained. In the AISS, the consistency, amount, and color of stools are described. The BITSS consists of photographs of diapers containing different types of stool. The BSS, on the other hand, is not age specific and only describes stool consistency. Consequently, the AISS is better adapted for children defecating in diapers and should therefore be used in preference to the BSS in this patient group. A recent multicenter study including parents, nurses, and doctors showed that 72.8% of participants matched the pictures of the BITSS correctly with categories of the BSS, and it was a reliable instrument for assessing stools in children who are not yet toilet trained.

Gathering information about stool form can be challenging because parents may not directly observe all stools, and studies have shown that both parents and children have difficulties describing their stool consistency. ^, The child could describe his/her stools by using the modified Bristol Stool Form Scale for Children (mBSFS-C; Fig. 11.2 ). In the mBSFS-C, the original BSS is adapted by decreasing the number of stool categories from seven to five.

Physicians should ask about the presence of abdominal pain or distension, loss of appetite, fever, nausea, vomiting, weight loss or poor weight gain, problems with neuromuscular development, and psychological or behavioral problems. Furthermore, urinary incontinence and urinary tract infections are reported in a considerable number of children with constipation and fecal incontinence. ^, Dietary history and the history of previous treatment strategies for constipation should be investigated. Finally, it is essential to ask about important life events that might contribute to the development of retentive behavior such as death in the family, birth of a sibling, school problems, and sexual abuse.

Physical Examination

A thorough physical examination should be performed in all children and should start with measurement of weight and height. Abdominal examination provides valuable information concerning the accumulation of gas or feces. Palpable fecal masses are present in 50% of children with chronic constipation. Evaluation of the perianal region provides valuable information about the position of the anus, evidence of fecal incontinence, skin irritation, eczema, fissures, hemorrhoids, and signs of possible sexual abuse. The anorectal digital examination assesses the perianal sensation, anal tone, size of the rectum, and contraction and relaxation of the anal sphincter. However, a digital rectal exam is not necessary for the diagnosis if the child already fulfills two other clinical Rome IV criteria for functional constipation. The lumbosacral area should be inspected for the presence of a sacral dimple, a tuft of hair, or asymmetry of the buttocks, which may indicate spina bifida occulta.

Laboratory Investigations

The European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) formulated in their recommendations that routine laboratory testing to screen for hypothyroidism, celiac disease, and hypercalcemia is not recommended in children with constipation in the absence of alarm symptoms.

These recommendations are in line with a recent study showing that only a minority of the children with constipation who undergo routine laboratory testing are diagnosed with a new organic disease. Only 1.7% were diagnosed with celiac disease, only 0.6% with hypothyroidism, and none with hypercalcemia. The likelihood of finding an organic cause decreases even further in children who present with constipation as their only symptom.

Evidence is conflicting for allergy testing to diagnose CMP allergy in children with functional constipation and is therefore not recommended. Two studies reported that 68% to 78% of children affected by constipation and CMP allergy improved after a CMP- elimination diet. ^, Both studies were performed in an allergy center, which could have led to an overestimation of the prevalence of this association. More importantly, the authors did not use the double-blind provocation test that is considered the gold standard method for diagnosing allergy to a food antigen. A subsequent prospective study conducted in Italy in 91 patients affected by chronic constipation did not confirm this association. Still, a 2- to 4-week trial of avoidance of CMP might be indicated in a child with intractable constipation.