Introduction
Fecal soiling in the pediatric population is a common and often underappreciated issue. Once children pass the toilet-training years and enter school, fecal soiling is seen as a taboo subject and is rarely discussed, even with the child’s primary care provider. Children and families are then left in the dark as they continue to suffer with the stress and other psychosocial effects of untreated fecal incontinence. The true prevalence of functional constipation and fecal incontinence is hard to ascertain. Recent meta-analyses cite a pooled global prevalence of 9.5% for functional constipation, ranging from 0.5% to 32.2%. Fecal incontinence, which is less studied, has a reported pooled prevalence of 0.4%, ranging from 0% to 1.8%. However, another study revealed an alarming 21%–50% of children with a defecation disorder did not disclose their symptoms to anyone, with most constipated children reporting “normal” stool frequency. Rates of pediatric fecal incontinence and constipation are therefore likely to be much higher than reported.
While rates of fecal incontinence and constipation are difficult to measure, the impact on children’s quality of life, and the associated family stress, is well-documented. Children with functional constipation had significantly lower Health-Related Quality of Life (HRQoL) scores compared with children without functional gastrointestinal disorders. Moreover, children with both constipation and fecal incontinence have poorer HRQoL compared to children with constipation alone. Over time, these children experience frequent school absenteeism and bullying. Parental stress related to their children soiling at inappropriate times is also common. Parents report significant anxiety and worry about their children with fecal incontinence. There is associated parental loss of work, transport cost, frequent hospitalizations, or clinic appointments that cannot be measured in formal studies.
Fecal incontinence and constipation place significant strain on the healthcare system, and their effects are increasing. While most treatment for pediatric constipation occurs in the outpatient setting, almost 40% of children hospitalized for constipation and disimpaction did not present to an outpatient clinic prior. Inpatient care for children with constipation has risen over the years within the United States. One study found that the healthcare cost for children with constipation is significantly higher than children with chronic disorders like asthma. In another study, over 10% of children were diagnosed with constipation in a pediatric emergency department visit for abdominal pain, further driving up healthcare costs. While viewed as a “mild disease,” fecal incontinence and constipation in children have significant impacts on quality of life and healthcare expenditure, and future treatments should be standardized to provide effective care.
Normal Fecal Continence
In order to best treat fecal incontinence and constipation, understanding the mechanisms for normal continence is important. Normal expulsion of stool requires voluntary and involuntary signals that create enough force for passage of stool through the anal opening. Colons with normal motility propel stool distally toward the rectum. As more stool enters, the rectum distends until at a certain level of stretch (which differs in each patient), the internal anal sphincter relaxes and sends signals to the brain to indicate an urge to defecate. Voluntary signals from the brain then induce relaxation of the external anal sphincter and contraction of abdominal muscles, while the anorectal angle straightens to allow gravity to facilitate emptying. The rectum contracts and expels stool through the straightened anal canal. At the same time, internal and external sphincters relax while the puborectalis muscles contract to effectively allow stool to pass. Thus, proper evacuation of stool, at the right place and right time, depends on a complex interplay of anatomical and psychological factors: intact voluntary pelvic muscles, anal canal sensation, colon motility, and psychological capacity ( Fig. 34.1 ).
Normal evacuation of stool requires a complex interplay of anatomical and psychological factors (in blue ). Alterations of the mechanisms (in red ) can disrupt this process. RAIR = rectoanal inhibitory reflex. HD = Hirschsprung disease.
Embedded image taken from Tran DL, Sintusek P. Functional constipation in children: what physicians should know. World J Gastroenterol . 2023;29(8):1261–1288. https://doi.org/10.3748/wjg.v29.i8.1261 . PMID: 36925458; PMCID: PMC10011959.
Voluntary pelvic muscle structures, namely the levators, external anal sphincter muscle complex, and parasagittal fibers, contract only when stool reaches the anorectal junction. Voluntary control of the external anal sphincter is not fully developed at birth and is typically achieved near the ages of 18–24 months. Relaxation of these muscles requires adequate muscle innervation and coordination.
The dentate line is a histologic transition zone between the squamous and columnar epithelium within the anal canal. Sensation of stool, and differentiation of stool from gas, is attributed to the dentate line. Innervation of the anal canal above the dentate line is from the autonomic system from the inferior hypogastric plexus. Parasympathetic nerve fibers inhibit the internal anal sphincters, while sympathetic nerve fibers maintain the tone of these sphincters. Intact internal anal sphincters provide the involuntary tone necessary to hold stool, but must also relax at the right time to allow for evacuation of stool. These signals to the internal anal sphincters are mediated by distension of the upper anal canal. Below the dentate line, anal canal sensation is mediated by the somatic nervous system from pudendal nerve branches.
Stool must also reach the rectum at regular, predictable intervals, and this is dependent on proper colonic motility. Each colonic segment must work in unity to propel stool forward effectively. Once stool reaches the rectum, the rectoanal inhibition reflex (RAIR) is initiated, and the internal anal sphincter relaxes. At this point, voluntary muscles either contract (to hold) or relax (to evacuate) stool.
Perhaps the least understood, but important, component of normal stool continence is psychological readiness. It is for this reason that toilet training is not fully achieved until the toddler years. Significant neurodevelopment delay, including the autism spectrum, can preclude the ability to stool properly even in the presence of normal anatomic structures. Much of the voluntary relaxation and contraction of pelvic muscle structures require a level of self-awareness that children with delays may not be able to achieve. On the other hand, this self-awareness can be developed in select patients through biofeedback and pelvic floor therapy.
Pseudoincontinence Versus True Incontinence
Fecal incontinence in children is formally defined as the repetitive, unintentional stool passage in inappropriate places in children who are developmentally 4 years old or older. It is classified broadly as true incontinence versus pseudoincontinence. Children with true fecal incontinence lack a key anatomic element necessary for voluntary bowel movements, such as poorly developed anal sphincters or a damaged dentate line. Typically, true fecal incontinence is the involuntary evacuation of stool in the absence of constipation. Conversely, pseudoincontinence is the involuntary evacuation of stool usually in the presence of severe constipation. Rarely, pseudoincontinence can also result from hypermotility. Also known as “overflow incontinence,” pseudoincontinence occurs when only liquid stool can pass around impacted stool within the rectum and through the anus.
Differentiating between true fecal incontinence and pseudoincontinence is the first step in treatment and should not be overlooked. Patients with true fecal incontinence typically require daily retrograde rectal enemas, or antegrade flushes via a Malone appendicostomy or cecostomy, to keep the rectum empty of stool that would otherwise leak out. Pseudoincontinence requires treatment of constipation, such that rectal stool is properly evacuated to prevent overflow, or treatment of hypermotility, which focuses on slowing the colon and changing stool consistency to allow for better voluntary control. Review of serial radiographs and a detailed history will usually reveal the type of incontinence ( Figs. 34.2 and 34.3 ).
Abdominal x-ray of fecal impaction.
A large amount of stool is seen within rectum, sigmoid, and descending colon in this abdominal x-ray. This patient reported large stool evacuation every few days, and multiple liquid accidents throughout the day, suggestive of overflow stool incontinence.
Abdominal x-ray of a hypermotile colon.
This x-ray demonstrates a colon clean for stool throughout, even in the ascending portion, suggestive of hypermotility. This child reported frequent loose stools and smearing of underwear throughout the day.
Incontinence by Diagnoses
Anorectal Malformation
Children with anorectal malformations (ARM) have varying degrees of pelvic floor muscle development. Depending on the type of malformation, this can range from nearly normal voluntary muscles to none. Approximately half of patients with ARM suffer from true fecal incontinence due to lack of voluntary muscles. These patients also lack normal anal canal sensation and do not have a dentate line. Colonic motility is largely intact, except for the child who has had longstanding constipation after posterior sagittal anorectoplasty (PSARP) resulting in a dilated, and thus dysmotile, rectum. In turn, this dilated rectum can hold more stool, and soiling occurs when stool overflows, resulting in pseudoincontinence. Dilation of the rectum can also affect its inherent motility and ability to properly signal the urge to defecate. Recent studies have noted soiling and constipation in over half of ARM patients in the long term. Up to two-thirds of ARM patients report soiling in underwear that improves with constipation treatment, which supports the notion that most of the fecal incontinence in ARM patients is due to pseudoincontinence.
There are key clinical features that can help define the continence prognosis in ARM patients ( Table 34.1 ). These factors include the type of malformation, sacral development, and the presence of spinal cord anomalies. Good prognosis is associated with a low malformation, a sacral ratio greater than 0.7, and a normal spine. Conversely , poor prognosis is associated with high malformations, a sacral ratio less than 0.4, and spinal anomalies such as a tethered cord. Providing parents with this information will help alleviate stress related to toilet training. Moreover, these clinical data can help inform bowel management choices. Children with good prognosis for fecal continence can be trialed on laxatives alone unless associated with longstanding constipation and a dilated rectum, in which case a temporary trial with daily enemas and a careful laxative trial would be more appropriate. Patients with defects associated with poor prognosis will likely need to start on enemas to remain clean.
Table 34.1
Continence Predictor Index
| Points | |||
|---|---|---|---|
| ARM TYPE | Perineal fistula | 1 | |
| Rectal stenosis | 1 | ||
| Rectal atresia | 1 | ||
| Rectovestibular fistula | 1 | ||
| Rectobulbar recto urethral fistula | 1 | ||
| Imperforate anus without fistula | 1 | ||
| Cloaca <3 cm common channel | 2 | ||
| Rectoprostatic fistula | 2 | ||
| Rectovaginal fistula | 2 | ||
| Rectobladderneck fistula | 3 | ||
| Cloaca >3 cm common channel | 3 | ||
| Cloacal exstrophy | 3 | ||
| SPINE | Normal termination of the conus (L1–L2) | 1 | |
| Normal filum appearance | 1 | ||
| Abnormally lowtermination of the conus (below L3) | 2 | ||
| Abnormal fatty thickening of filum | 2 | ||
| Myelomeningocele | 3 | ||
| SACRUM | Sacral ratio = greater than 0.7 | 1 | |
| Sacral ratio = between 0.4 and 0.69 | 2 | ||
| Hemisacrum | 2 | ||
| Sacral hemivertebrae | 2 | ||
| Presacral Mass | 2 | ||
| Sacral ratio = less than 0.4 | 3 | ||
This index can be used as a tool to predict continence potential. A lower score is better. A total of 3–4 points portends a good continence potential, while 5–6 points suggests only a fair potential, and 7–9 points indicate a poor potential for continence.
Hirschsprung’s Disease
Patients with Hirschsprung’s disease (HD) are born with intact pelvic floor muscles. Iatrogenic damage to the anal sphincter at the time of pullthrough can occur and may contribute to true fecal incontinence. On anorectal exam under anesthesia, findings consistent with damage to the anal sphincter include a patulous anus with a preserved dentate line. Similarly, although patients with HD have an intact anal canal and dentate line at birth, one or both can be damaged at pullthrough ( Fig. 34.4 ). In terms of motility, HD patients lack a RAIR. In addition, postoperative HD patients undergo resection of their aganglionic colon. Depending on the length of aganglionic bowel, HD patients can suffer from true fecal incontinence due to hypermotility. The majority, however, suffer from constipation and subsequent pseudoincontinence. Remaining ganglionated colon has various levels of dysmotility despite optimal pullthrough, though the mechanisms for this are not currently well understood. Combined with absent RAIR, most HD patients benefit from treatment of constipation with stimulant laxatives.
Obliterated dentate line in a postpullthrough patient.
This patient had undergone a pullthrough procedure earlier in life and an anorectal exam under anesthesia was performed due to soiling. Findings were consistent with an obliterated dentate line.
Clinicians must differentiate if an HD patient is suffering from constipation, true incontinence, or postoperative obstruction. Guidelines for investigating soiling after pullthrough were recently proposed by the APSA Hirschsprung Disease Interest Group ( Fig. 34.5 ). Symptoms of recurrent enterocolitis, abdominal distension, and failure to thrive are not associated with constipation. Rather, these clinical signs warrant urgent further workup to determine possible anatomical obstruction or transition zone pullthrough. Additionally, treatment should not employ aggressive laxative use, as it can worsen distension. Effective irrigations to rid the colon of stool and bacteria, along with antibiotics, should be the mainstay of treatment. Botulinum toxin injection can help relax the internal anal sphincter, at least temporarily, to allow for passage of stool in the absence of a RAIR in these children.
Proposed algorithm for workup of soiling in the post pullthrough Hirschsprung’s disease patient.
Determination of causes for soiling after pullthrough should be performed in a step-wise manner so as to differentiate between true and pseudoincontinence.
From Saadai P, Trappey AF, Goldstein AM, et al. Guidelines for the management of postoperative soiling in children with Hirschsprung disease. Pediatr Surg Int . 2019;35:829–834.
Neurogenic Bowel
Children with neurogenic bowel may have one of several underlying diagnoses, including myelomeningocele, spina bifida, cerebral palsy, acquired brain and spinal cord injuries, and congenital tethered cord. Children with tethered cord or other congenital spinal anomalies alone are typically born with intact voluntary pelvic muscles and anal canal, but do not have normal bowel motility. Most are hypomotile and stool requires more time to pass through the colon and into the rectum. The mean rectal pressure, or level of distention, that precipitates the cascade that results in proper defecation is typically higher in children with neurogenic bowel. Up to 90% of children with cerebral palsy have constipation, with 47% suffering from fecal incontinence. Children born with spina bifida, myelomeningocele, and other similar conditions will inherently have weaker pelvic floor muscles. Sensation in the distal portion of the anal canal, distal to the dentate line, may not be intact as well. Depending on the child’s presentation, they may be suffering from pseudoincontinence secondary to constipation or true incontinence due to lack of pelvic floor muscles.
The level of spinal defect or injury relative to the conus medullaris yields two distinct patterns that ultimately result in constipation and fecal incontinence. Above the conus medullaris, there is loss of inhibitory neural input resulting in increased anal sphincter tone and stool retention. Additionally, there is hyperreflexia distal to the splenic flexure and hypertonia of the rectum, both resulting in fecal incontinence. Below the conus medullaris, the parasympathetic cell bodies are damaged, and the autonomic motor nerves are disrupted. Rectal tone is significantly decreased or absent, with reduced amplitude of the RAIR. Rectal filling does not result in internal anal sphincter relaxation, leading to constipation, but with reduced resting anal pressures, stool leaks frequently.
Due to the variable diagnoses that result in neurogenic bowel, measuring bowel dysfunction in these children is difficult. Several tools for measurement have been developed, such as a neurogenic bowel dysfunction score, but require larger studies for validation. Patients with neurogenic bowel are typically not responsive to increasing doses of laxatives and do well with rectal enemas or transanal irrigations such as Peristeen ( Fig. 34.6 ). Urinary incontinence is often a concurrent issue, but treatment of fecal incontinence and constipation will often improve urinary symptoms. As these children seek independence, they may be candidates for a Malone appendicostomy and Mitrofanoff vesicostomy.
Peristeen transanal irrigation.
The system consists of (1) rectal catheter with inflatable balloon, (2) pump for activating balloon and flushing water, (3) regulatory control unit for air and water, and (4) bag for water.
From Pacilli M, et al. Use of Peristeen(R) transanal colonic irrigation for bowel management in children: a single-center experience. J Pediatr Surg . 2014;49(2):269–272; discussion 272.
Severe Idiopathic Constipation
Idiopathic constipation is essentially a diagnosis of exclusion. Children presenting with encopresis are typically suffering from chronic constipation, but parents and caregivers mistake the fecal soiling as diarrhea. Often, children are deemed to have behavioral problems (i.e., child refuses to sit on the toilet to stool, so will soil themselves elsewhere) rather than severe constipation. Indeed, more than a third of children present with behavioral problems primary or secondary to constipation, so determining the underlying cause can be difficult.
Establishing the diagnosis of constipation is aided by the Rome IV criteria ( Table 34.2 ). A thorough history and physical should focus on stool consistency, frequency, and signs of possible congenital abnormalities. A complete list of medications should be obtained, as many are associated with constipation. Failure to thrive, abdominal distention, vomiting, and other similar symptoms should prompt urgent evaluation.
Table 34.2
Rome IV Criteria
| Symptoms (Two or More Present) |
|---|
|
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