In more than 99 % of healthy term neonates, the first meconium passes within the first 48 h of life [5, 6]. Delayed passage of the first meconium beyond the first 48 h of life is suggestive for an organic defecation disorder (e.g., Hirschsprung’s disease). During the first months of life, the defecation frequency may vary from child to child, this is partially dependent on feeding type; breastfed children have a higher defecation frequency than formula-fed infants [6]. In the first weeks of life, the defecation frequency lies around 4 stools a day, this frequency gradually decreases over time until it is approximately once a day in children at the age of 4 years [6, 7]. In older children, defecation usually occurs either daily or every other day [8].

The physiological dynamics of defecation are complex and rely on several intricate processes involving the autonomic and somatic nervous system, the pelvic floor muscles, and the internal and external anal sphincters. In the colon, feces is propelled by propagating colonic contractions. Several different colonic motor patterns have been described [9, 10], but the most well-recognized propagating motor patterns are high-amplitude propagating contractions (HAPCs ). These motor patterns are associated with the mass movement of colonic content and spontaneous defecation in healthy adults [11, 12]. Anterograde propagation of feces through the colon leads to filling of the rectum, which induces a relaxation of the internal anal sphincter, allowing feces to travel further down the anal canal; this reflex is known as the recto-anal inhibitory reflex (RAIR ). Subsequently, sensory stimuli caused by rectal distension and by the contact between fecal material and the mucosa of the proximal part of the anal canal result in an urge to defecate. At this point, voluntary contraction of the external anal sphincter can postpone defecation, by moving the fecal load back, higher up in the anal canal and rectum, until the place and time are appropriate for defection. When defecation is initiated, voluntary relaxation of the external anal sphincter and the pelvic floor musculature (i.e., the puborectalis muscle and levator ani) allows for an easy defecation process. In young children, this can be promoted by proper support of the feet when sitting on the toilet and a relaxed posture. Then, by gently increasing the intra-abdominal pressure, stools can be expelled from the rectum.

FC occurs in children of all ages, but there are three phases in life when children seem to be more prone to develop constipation: (1) in infancy, concomitant with changes in feeding (e.g., change from breastfeeding to formula-feeding, introduction of solid foods); (2) around the time of toilet training; and (3) in school children who avoid going to the toilet at other places than home [13]. This suggests that both dietary and behavioral factors play an important role in the pathogenesis of FC.

One important recognized etiologic factor, especially in young children, is stool withholding behavior. This often occurs after a negative experience such as a hard, painful, or frightening bowel movement [14]. Stool withholding behavior can lead to the accumulation of a large fecal mass in the rectum that is difficult to evacuate, also known as fecal impaction. Fecal impaction may lead to overflow fecal incontinence which is the involuntary loss of soft stools that pass the solid, obstructing, fecal mass. Stool withholding can lead to a negative chain of events; due to a painful defecation experience, the child voluntarily retains the stools in an attempt to prevent another painful bowel movement, causing the stools to become harder and more difficult to evacuate, leading to more pain during defecation. Withholding behavior may eventually lead to dyssynergia, this occurs when the coordination of the muscles involved in defecation are inadequately coordinated during defecation. Instead of relaxing the muscles involved in normal defecation, muscles are tightened in a poorly coordinated attempt at defecation, preventing stools to be expelled from the rectum and sustaining constipation.

Propagation of feces through the colon is an essential step in the physiology of defecation. In children with long-standing symptoms of FC the passage of feces through the colon is often delayed [15]. It is not entirely clear whether this delay in colonic transit time plays a causative role or if it is an effect of long-standing constipation and becomes a perpetuating factor, resulting in a detrimental causal sequence.

Studies utilizing colonic manometry have revealed that in children with intractable FC, several types of colonic dysmotility can be differentiated. In healthy humans, stretching of the stomach after a meal induces an increase in motility of the colon, this response is known as the gastrocolic reflex. Colonic manometry studies have shown that this reflex is impaired in a subset of children with FC, which may indicate an impaired extrinsic innervation [16, 17]. Furthermore, it has been shown that a proportion of children with FC have incompletely propagating HAPCs or a general lack of HAPCs in response to a stimulant laxative, which likely implies an intrinsic (neurogenic or myogenic) pathophysiological process. Once again, it remains uncertain whether these findings are cause, effect, or a combination of both.

Although the precise underlying pathophysiological mechanisms are not always clear, psychosocial factors such as major life events, socioeconomic status, educational level, and parental child-rearing attitudes might play a role in the pathophysiology of FC [3, 18, 19]. Furthermore, behavioral disorders such as autism spectrum disorders and attention deficit hyperactivity disorder are associated with a higher risk of childhood constipation [20, 21].

Since FC seems to occur more often in certain families, genetic factors may contribute to the etiology of childhood constipation [22]. However, studies have failed to identify mutations in specific genes associated with FC [23].

Gut microbiota differences have been identified between children with and without FC, suggesting that gut microbiota may play a role in the pathogenesis of FC [24]. One of the possible mechanisms in which the gut microbiota may potentially influence gut motility is by the production of methane as a consequence of anaerobic fermentation of carbohydrates and the production of hydrogen in the gut [25]. There is strong evidence from animal studies that methane delays intestinal transit, possibly acting as a neuromuscular transmitter, and methane production has been associated with constipation in adults [25–27].

There has been an increasing interest in bile salt metabolism as a potential pathophysiological factor in FC; deconjugated bile salts have the potential to function as endogenous laxatives by increasing colonic motility and fluid secretion [28, 29]. In a subset of children with FC, bile acid metabolism has been shown to be altered, leading to a decreased secretory activity. This suggests that bile acid metabolism may play a role in the pathophysiology of constipation in a subset of children [30].

In the medical history , questions should address defecation frequency, stool consistency, painful bowel movements, size of the stools, episodes of fecal incontinence, and a history of withholding behavior (Table 42.1). Keeping a daily bowel diary can be useful to gather reliable information about a child’s bowel habits. The Bristol Stool Scale or the Modified Bristol Stool Form Scale for Children can be helpful in the assessment of stool consistency [31]. Special attention should be paid to questions about withholding behavior, as this behavior may not be recognized as such by parents and may even be wrongfully interpreted as straining to defecate. Questions regarding stool withholding behavior should therefore be clear and illustrated with examples. In infants, withholding may be characterized by grunting, arching of the back, and tightening of the legs. In toddlers, squeezing the buttocks together, crossing the legs, standing on the toes, and rocking back and forth are distinctive signs of withholding. The medication history should include the use and efficacy of oral laxatives, enemas, and other medications that potentially influence gastrointestinal motility.

Assessment of weight and height is of key importance since detection of failure to thrive may be a sign of an organic cause of constipation. A physical examination may be helpful in diagnosing constipation and is especially important in detecting alarm signs. It primarily consists of examination of the abdomen, the perianal region, and the lumbosacral region.

Abdominal examination mainly focuses on the detection of a palpable fecal mass or scybala. Perianal inspection should be performed in all children; the physician should look for anatomic abnormalities, perianal feces, fissures, scars, and erythema. The presence of fissures can be a sign of hard or large stools, but can also be a sign of sexual abuse. Hematomas in the perianal region are highly suspicious of abuse. Special attention should be paid to abnormal behavior during physical examination (e.g., sexual acting out, extreme fear) [35]. Although digital rectal examination provides valuable information on the presence of a rectal fecal mass, anorectal sensation, and sphincter tone, it is not necessary for the diagnosis of FC if a child already fulfils 2 or more Rome III criteria (Table 42.1) [2]. If a child fulfils one of the Rome III criteria, a digital rectal examination is recommended since it may help establish the diagnosis of FC. Examination of the lumbosacral region may reveal the presence of a dimple, a tuft of hair, or gluteal cleft deviation, indicative of an organic cause of constipation (e.g., spina bifida).

Laboratory testing (e.g., for hypothyroidism, celiac disease, or hypercalcemia) in children with constipation is only indicated when there is a suspicion for an underlying organic disease, it does not belong in the routine workup of children with FC.

Manometry allows for measurement and quantification of intraluminal pressure and contact force in the gastrointestinal tract; this technique can be utilized to gain insights into gastrointestinal motility.

Education is the first step in the non-pharmacological treatment of FC [58]. This should include an explanation of physiological defecation dynamics, tailored to the developmental age of the child. The negative chain of events that may have been prompted by a painful defecation experience should be explained to parents and, if possible, children. It is important to describe the pathophysiology of overflow incontinence and the pivotal role that withholding behavior plays in this process.

Because stasis of feces in the rectum can maintain constipation, it is important to evacuate the rectum regularly. In children with a developmental age of ≥4 years, this can be established by introducing a toilet training program, with scheduled toilet sits throughout the day, usually after every meal and after coming home from school. The toilet sits are scheduled after a meal to benefit from the gastrocolic reflex which increases colonic peristalsis upon distension of the stomach. To motivate children to maintain this toilet training program, a reward system can be introduced. By rewarding the child with small gifts for completing toilet trainings, the child is positively reinforced to comply with therapy. A nonaccusatory approach of both physicians and parents is of key importance since children may feel guilty or embarrassed, especially about episodes of fecal incontinence [58]. Only rewarding periods without fecal incontinence is therefore not recommended, this may increase feelings of guilt and can be experienced as punishment for having fecal incontinence.

Studies on the use of probiotics have been conducted in children, but to date, there is insufficient evidence to support the use of probiotics in the treatment of childhood constipation [60, 63].

Biofeedback training utilizes reinforcing stimuli in an attempt to achieve a recognizable sensation and encouraging an appropriate learnt response. In theory, this may help children with dyssynergia to adapt their defecation dynamics. However, currently available evidence does not support the use of biofeedback training for the treatment of childhood constipation [64].