This article reports the clinical, physiopathologic, diagnostic, and therapeutic aspects of the most common anorectal disorders in children. In particular, it focuses on the differential diagnosis between organic and functional constipation. In addition, the authors separately examine some of the clinical conditions such as atopy, neurologic diseases, and anorectal malformations, in which chronic constipation may be an important clinical manifestation.
Anorectal disorders include a diverse group of functional and pathologic conditions that cause significant patient discomfort and disability. They are common in children and are usually mild and short-lived if the child receives prompt and adequate attention during the early phase of the disorder. Frequently, however, the child presents long after the appearance of initial symptoms, when the symptoms may have become more difficult to treat. Altered stool frequency and altered behavior with defecation are common presenting symptoms in children who have anorectal disorders. These alterations may be affected by several factors such as diet, social habit, convenience, parents’ cultural beliefs, interrelationships within the family, and daily timing of activities. In addition, all of the previously described factors may vary in relation to the age and the degree of psychophysical development of the child. It has been estimated that 10% of children are brought to medical attention because of an anorectal disorder, and constipation is the chief reason for these visits to pediatricians.
This article reports the clinical, physiopathologic, diagnostic, and therapeutic aspects of the most common anorectal disorders in children. In particular, it focuses on the differential diagnosis between organic and functional constipation. In addition, the authors separately examine some of the clinical conditions such as atopy, neurologic diseases, and anorectal malformations, in which chronic constipation may be an important clinical manifestation.
Constipation
Constipation is a symptom rather than a disease and often constitutes a major problem for the child and his or her family. Unfortunately, there is no universally accepted definition of chronic constipation. Recently, a group of pediatric gastroenterologists and pediatricians with an interest in gastrointestinal (GI) motility reached agreement on defining childhood functional defecation disorders. Based on this consensus, constipation was defined as the occurrence of two or more of the following six characteristics during the previous 8 weeks:
Two or less bowel movements in the toilet per week
One or more episodes of fecal incontinence per week
History of retentive posturing and withholding behavior
History of painful defecation
Presence of large stools in the rectum or palpable on abdominal examination
History of large diameter stools that may obstruct the toilet
The group also adopted the term fecal incontinence to replace the terms encopresis and soiling. With 84% of constipated children suffering from this disorder, the involuntary passing of fecal material in the underwear is one of the major features of childhood constipation. Hence, it is important to distinguish between constipation with fecal incontinence and functional nonretentive fecal incontinence (FNRFI), because different pathophysiological mechanisms are involved. Both entities can result in fecal incontinence, but in children who have FNRFI, there are no signs of constipation. In many studies, constipated children who have fecal incontinence and children who have FNRFI are grouped into one study population, because both groups have fecal incontinence. Nevertheless, about 80% of children who have fecal incontinence experience chronic constipation.
The normal frequency of bowel movements at different ages has been well- characterized ( Table 1 ).
| Age | Bowel Movements Per Week a | Bowel Movements Per Day b |
|---|---|---|
| 0–3 months | ||
| Breast-fed | 5–40 | 2.9 |
| Formula-fed | 5–28 | 2 |
| 6–12 months | 5–28 | 1.8 |
| 1–3 years | 4–21 | 1.4 |
| More than 3 years | 3–14 | 1.0 |
Infants have a mean of 4 stools per day during the first week of life. This frequency gradually declines to a mean average of 1.7 stools per day at 2 years of age and 1.2 stools per day at 4 years of age. Some normal breast-fed babies do not have stools for several days or longer. After 4 years, the frequency of bowel movements remains unchanged.
A normal pattern of stool evacuation is thought to be a sign of good health in children of all ages. Often, during the first months of life, parents pay close attention to the frequency and characteristics of their child’s defecation. Any deviation from what is thought by a family member to be the norm for the child may trigger a call to the nurse or a visit to the pediatrician. In fact, chronic constipation is a source of anxiety for parents who worry that it may be a symptom of serious disease.
Epidemiology
Constipation is the main complaint in 3% of pediatric outpatient visits.
This percentage increases to 25% to 45% in specific pediatric–GI motility clinics. To date, the worldwide prevalence of constipation in children varies widely and is estimated to range between 0.6% and 29.6%. This wide range could be caused by differences in survey methods, age distribution, or definition.
Organic causes actually affect less than 10% of children presenting with constipation. In children who have cerebral palsy or autism, constipation is reported in 26.5% to 74% of subsets.
In very low birth weight infants (<750 g), constipation is very common (32%). When evaluated between 10 and 14 years of age, these children continue to experience higher rates of toileting problems such as encopresis and withholding behavior, and neuro-developmental impairment when compared with age-matched children of higher birth weight.
Some children may be genetically predisposed to developing constipation. A family history of constipation has been found in 28% to 50% of cases, and there is a higher incidence in monozygotic twins when compared with dizygotic twins. It has been reported that in some children constipation is associated with specific dermatoglyphic pattern. Constipation usually is reported to be more common in boys than in girls, with a 2:1 ratio, although some describe an equal prevalence between the sexes.
Epidemiology
Constipation is the main complaint in 3% of pediatric outpatient visits.
This percentage increases to 25% to 45% in specific pediatric–GI motility clinics. To date, the worldwide prevalence of constipation in children varies widely and is estimated to range between 0.6% and 29.6%. This wide range could be caused by differences in survey methods, age distribution, or definition.
Organic causes actually affect less than 10% of children presenting with constipation. In children who have cerebral palsy or autism, constipation is reported in 26.5% to 74% of subsets.
In very low birth weight infants (<750 g), constipation is very common (32%). When evaluated between 10 and 14 years of age, these children continue to experience higher rates of toileting problems such as encopresis and withholding behavior, and neuro-developmental impairment when compared with age-matched children of higher birth weight.
Some children may be genetically predisposed to developing constipation. A family history of constipation has been found in 28% to 50% of cases, and there is a higher incidence in monozygotic twins when compared with dizygotic twins. It has been reported that in some children constipation is associated with specific dermatoglyphic pattern. Constipation usually is reported to be more common in boys than in girls, with a 2:1 ratio, although some describe an equal prevalence between the sexes.
Physiology of defecation
A brief review of the physiology of defecation indicates that there are several motor patterns normally responsible for the movement of colonic contents:
Segmental, nonpropagated, phasic contractions mixing luminal contents
Powerful high-amplitude propagated contractions (HAPCs) that propel stools aborally
Changes in colonic tone
An increase in colonic motility and tone after a meal, also known as the gastrocolonic response, moves the stools from the more proximal colon to the rectosigmoid region. The HAPCs are the most powerful contractions found in the large bowel and are the manometric equivalent of the mass movements described in the radiologic literature. The descending fecal bolus distends the empty rectum, stimulating sensory receptors in the bowel wall and pelvic floor. Ascending sensory fibers allow conscious awareness of rectal distension. There is a transient contraction of the voluntary striated muscles, the external anal sphincter (EAS), and the puborectalis sling, the so-called inflation reflex. Transmission of the nerve impulse distally by the myenteric plexus of the lower rectal wall produces a reflex inhibition of the involuntary internal anal sphincter (IAS), the recto–anal inhibitory reflex (RAIR), and of the EAS involving reflex pathways. Several studies in term and preterm infants have shown that the RAIR is present in infants older than 26 weeks gestation. Relaxation of the puborectalis muscle allows widening of the anorectal angle (from resting 60° to 105° to 140°), resulting in an unobstructed anal canal. The increased abdominal pressure and rectal peristalsis result in expulsion of feces and emptying of the entire rectum. Before the acquisition of voluntary control, rectal distension results in EAS loss of electrical activity and tone (inhibition reflex). By 24 to 30 months of age, the maturation of myenteric ganglion cells is associated with persistence of EAS tonic activity mediated by a spinal reflex and augmented by supraspinal cortical centers, allowing the normal inflation reflex and conscious control of defecation.
The sensitive lining of the anoderm perceives the stool, and a conscious decision is made whether to expel it or to postpone defecation by contracting the external anal sphincter and the puborectalis muscle. If defecation is delayed to a later time, significant voluntary effort that includes contraction of the abdominal muscles and relaxation of the pelvic floor will be needed to push the stool into the anal canal and produce a bowel movement. If this sequence is difficult or cannot be produced effectively, constipation ensues.
Pathogenesis of functional constipation
The pathophysiological mechanisms that underlie childhood functional constipation are multifactorial, and not understood well. In 90% to 95% of patients, no specific organic cause can be found.
In some babies, an acute episode of constipation may occur associated with a change in diet. Passage of dry and hard stools may cause anal fissures and pain. Genetic predisposition may play a role, because constipation often dates back to the first months of life, and many patients have a positive family history of constipation.
The timing of toilet training is critical, because constipation may occur as a consequence of conflicts between the child and parents. Retentive posturing is probably the major cause for the development or persistence of constipation in toddlers.
Other causes of stool withholding behavior include the previous passage of large, hard, or painful stools; anal fissures; significant behavioral problems; lack of time for regular toileting; and distaste for toilets other than the child’s own.
When the retentive toddler experiences the urge to defecate, he or she assumes an erect posture and holds the legs stiffly together to forcefully contract the pelvic and gluteal muscles. Consequently, the rectum accommodates to its content, and the urge to defecate disappears. The retained stools become progressively more difficult to evacuate, leading to a vicious circle in which the rectum increasingly is distended by large fecal contents. Finally, chronic rectal distension may cause overflow incontinence, loss of rectal sensitivity, and in the end, loss of normal urge to defecate. This aberrant behavior may lead to the unconscious contraction of the external sphincter during defecation. Furthermore, abnormalities in rectal function were felt to be responsible for persistent complaints and relapses. Increased compliance of the rectal wall has been proposed as a contributing mechanism for intractable pediatric constipation. A recent study demonstrated that recovered adolescents had a lower rectal compliance when compared with patients who had functional constipation. In almost half of the recovered patients, however, rectal compliance was above the normal range.
Functional constipation
The term functional constipation’ describes all children in whom constipation does not have an organic etiology. Because functional constipation and functional fecal retention often overlap, the two disorders have been merged into one category termed functional constipation.
Approximately 40% of children who functional constipation develop symptoms during the first year of life, with a peak incidence during the time of toilet training, often between 2 and 4 years of age.
A careful history needs to elicit the time after birth of the first bowel movement, the time of onset of the problem, characteristics of stools, the presence of associated symptoms (pain at defecation or fecal incontinence), stool withholding behavior, urinary problems, and neurologic deficits. Fecal incontinence may be mistaken for diarrhea by some parents. Urinary problems are also common in these children.
Onset of constipation frequently occurs during one of three periods: 1) when the infant switched from breast milk to either formula milk or introduction of solids, 2) when the toddler is acquiring toileting skills and finds defecation painful, and 3) when the child starts school (they tend to avoid defecation throughout the school day).
The physical examination includes assessment of the size of the rectal fecal mass, which often is estimated by calculating the height above the pelvic brim with bimanual palpation on either side of the rectus sheath and rectal examination after establishing a relationship with the patient and the family. When the history is typical for functional constipation, the perineum should be inspected, but a digital rectal examination may be delayed to facilitate bonding between the child and the clinician or until failure of a treatment trial. If the clinician plans a single consultation without follow-up, a rectal examination is necessary to evaluate the child for a rare obstructing mass or fecal impaction.
External examination of the perineum and perianal area should exclude signs of spinal dysraphism.
A plain radiograph of the abdomen can be useful for determining the presence of fecal retention in a child who is obese or refuses rectal examination.
Diagnosis
Childhood functional constipation is a clinical diagnosis that can be made in most cases on the basis of a typical history and an essentially normal physical examination. In the absence of red flags, testing is neither necessary nor desirable ( Box 1 ). In atypical cases or when conventional treatment fails, the primary care physician may choose diagnostic tests to diagnose an organic cause or to consult with a subspecialist.
Onset of constipation <12 months of age
Delayed passage of meconium
No withholding
No fecal incontinence
Failure to thrive
Empty rectal ampulla
Pigmentary abnormalities
Heme-positive stools
Presence of extraintestinal symptoms
Bladder disease
No response to conventional treatment
The initial diagnostic workup includes serologic assays for celiac disease, evaluation of thyroid function in selected cases, and serum electrolytes, calcium level, allergic testing. Manometric studies usually are not indicated in the evaluation of adolescents who have defecation disorders. They are useful only in a subset of patients who have constipation that is refractory to treatment. The main indication for anorectal manometry is to demonstrate the presence of RAIR. The presence of RAIR excludes Hirschsprung’s disease. Other diagnostic tests such as colonic manometry, barium enema, colonic transit time, and rectal biopsy can be useful in selected cases.
Assessment of total and segmental colonic transit time (CTT) using radio-opaque markers provides accurate and reliable information about colorectal motor function in defecation disorders. The marker technique is used to localize the delay in colonic transit and is particularly helpful if bowel history is unreliable. Studies in children who have constipation show different colonic transit patterns: normal transit time, dyssynergic defecation-delayed transit through the anorectal region, and slow transit constipation-prolonged transit through the entire colon. Normal CTTs are found in 39% to 58% of constipated children. The most common type of delayed CTT in children is outlet delay caused by dyssynergic defecation. The radio-opaque marker test is useful for differentiating children who have constipation from those who have functional nonretentive fecal incontinence. Colonic transit abnormalities in both the left colon and rectum may be responsible for constipation in children who have severe brain damage.
Colonic manometry can be used to discriminate between functional and the rare neuromuscular causes of severe and therapy-resistant constipation. The markers for normal motility are the presence of HAPCs and the presence of a gastrocolonic response to a meal. In most children who have constipation, colonic motility is normal, showing HAPCs and an increase in motility in response to a pharmacologic stimulus or administration of a meal. In those patients who have colonic neuropathies, contractions are often present but may be disorganized with absence or incomplete propagation of the HAPCs. In patients who have myopathies, colonic contractions are absent or very weak and are unable to propel stool.
Management of children with functional constipation
The Childhood Constipation Working Group of the British Society of Pediatric Gastroenterology, Hepatology, and Nutrition recently reported that on the basis of a systematic review of available treatments, there was insufficient evidence to make any recommendations for practice, and that guidelines would need to be based on clinical experience, evidence, and consensus. The general approach to the child who has functional constipation includes the following steps: education, disimpaction, prevention of reaccumulation of feces, and follow-up.
A critical first step is to manage anxiety among parents and children. An important component of treatment includes behavior modification and regular toilet habits. The child may be fearful of painful defecation, and parents need to understand that coercive toilet training in this period of life will be ineffective. The child is instructed to attempt to defecate after meals three times daily for 5 minutes. The child is encouraged to strain actively while placing his or her feet on a footrest. In older children, fecal incontinence and its social consequences need a nonaccusatory management approach; it is essential to provide reassurance regarding the benign nature of this behavioral disorder.
The objectives of treatment are to remove fecal impaction, to restore a normal bowel habit with soft stools that can be passed without discomfort, and to ensure self-toileting and passage of stools at appropriate places. Disimpaction is indicated when a large fecal mass is present that is unlikely to be expelled without pain. This is accomplished best with oral medication or enemas. High doses of polyethylene glycol 3350 (1 to 1.5 g/kg/d for 3 days) have been shown to be effective. The use of suppositories, enemas, and manual evacuation is more contentious, and a careful balancing of physical and psychologic benefits and harms is necessary. Once impaction has been removed, the treatment should focus on preventing a recurrence. This treatment consists of dietary interventions, behavioral modification, and laxatives to assure that bowel movements occur at normal intervals with easy evacuation.
The association between fiber intake and constipation is still controversial. Two case control studies in children have examined fiber intake in constipated children compared with healthy controls. Discriminant analysis showed that only fiber intake was correlated independently with constipation. On the other hand, it has been demonstrated that constipated children generally do not consume less fiber than healthy children, and treatment with increased fiber intake did not result in clinical improvement. Two small double-blind placebo-controlled trials in 20 neurologically impaired constipated children and in 31 otherwise healthy constipated children showed beneficial effects on stool frequency, stool consistency, incontinence episodes, suppository use, and adverse effects for glucomannan, a fiber gel polysaccharide. Although the authors recommended an increased fiber intake in children who have constipation, larger clinical trials are needed to confirm these studies.
The aim of a combination of behavioral treatment (toilet training in combination with a rewarding system, diminishing of toilet phobia), cognitive (psychotherapy, cognitive therapy and family therapy, or educational intervention) and laxative treatment is to lower the level of distress and develop or restore normal bowel habits by positive reinforcement, preservation of self-respect, and encouragement of the child and parents during the treatment. In a large prospective randomized–controlled trial of 162 constipated children, a higher cure rate was found in children receiving behavioral intervention (toilet training, positive reinforcing scheme, and dietary advice) plus laxatives (polyethylene glycol, oral and rectal bisacodyl, followed by a long-term treatment of mineral oil plus phenolphthalein) compared with those receiving solely behavioral intervention at both 6 and 12 months of follow-up. In a randomized– controlled trial of 87 constipated children (8.6 ± 2.0 years), enhanced toilet training (intensive medical treatment plus behavior management) was more effective than either intensive medical treatment or biofeedback training, although the difference was not statistically significant.
Once disimpaction has been achieved, it is essential to begin an oral daily laxative immediately and continue treatment for several months to prevent reaccumulation of retained stools and recurrence of stool withholding behavior. Osmotic laxatives, stimulant laxatives, and prokinetics are recommended. Recently, polyethylene-glycol (PEG) has been suggested as a laxative in adults and children who have constipation. The correct dose is that which produces a daily evacuation of soft stool without adverse effects.
In children, uncontrolled, unblinded, and randomized–controlled studies have been performed to assess the effects of PEG. These studies have reported the effects of PEG at low doses, with mean effective doses ranging from 0.6 to 0.8 g/d. A double-blind, randomized–controlled trial showed that both PEG and lactulose significantly increase stool frequency and decrease the frequency of incontinence. Abdominal pain, straining, and pain with defecation decreased significantly; however, more children on PEG complained about the bad taste. Controlled studies of PEG in childhood constipation show that neither PEG 4000 (without added salts at 4 to 8 g) nor lactulose at 3.3 to 6.6 g induced any change in blood electrolytes, total protein, serum albumin, or vitamins A and D over a 3-month period. These studies confirm the efficacy and safety of PEG 4000 in childhood constipation. In addition, a more recent randomized, double-blind crossover trial showed that PEG 3350 plus electrolytes is significantly more effective than placebo for treating chronic constipation in children. The doses of these medications are reported in Table 2 . Discontinuation should be considered only when the child is having regular bowel movements and without difficulty. Although 60% of all children referred to a tertiary medical center for chronic constipation were treated successfully at 1 year follow-up by intensive medical and behavioral treatment, however, one third of the children followed-up beyond puberty continued to have severe complaints of constipation.
| Medications | Treatment Adverse Effects and Comments | Quality of Evidence |
|---|---|---|
| Oral administration | ||
| Lubricant | Softens stool and eases passage | |
| Mineral oil: <1 year-old not recommended; disimpaction 15–30 mL/y of age, up to 240 mL daily for maintenance 1 to 3 mL/kg/d given once daily or in divided doses twice daily | Chill or give with juice; risk of lipoid pneumonia; adherence problems; leakage may occur if dose is too high or impaction is present. | In children: I |
| Osmotic laxatives | Retain water in stool, which adds bulk and softness | |
| Lactulose (concentration: 10 g/15 mL): 1 to 3 mL/kg/d given in divided doses twice daily | Abdominal cramping, flatus; lactulose is a synthetic disaccharide | In infants: III |
| In children: I | ||
| Magnesium hydroxide (milk of magnesia; concentration: 400 mg/ 5 mL): 1 to 3 mL/kg/ d given in divided doses twice daily magnesium hydroxide (concentration: 800 mg/5 mL): 0.5 mL/kg/d given in divided doses twice daily | Infants are susceptible to magnesium poisoning; with overdose or renal insufficiency: risk of hyperrmagnesemia, hypophosphatemia, or secondary hypocalcemia | In children: I |
|
| In children: III |
| Sorbitol: 1 to 3 mL/kg/d given in divided doses twice daily | Less costly than lactulose | In infants: III |
| In children: I | ||
| Stimulants | Short-term use only; improves effectiveness of colonic and rectal muscle contractions | |
| Senna syrup (8.8 g sennoside per 5 mL) | Risk of idiosyncratic hepatitis, melanosis coli, hypertropic osteoarthropathy, analgesic nephropathy, abdominal cramping; melanosis coli improves after medication is stopped; tablets and granules are available | In children: II–I |
| Age 2–6 years: 2.5–7.5 mL/d given in divided doses twice daily | ||
| Age 6–12 years: 5–15 mL/d given in divided doses twice daily | ||
| Bisacodyl (5 mg tablets): one to three tablets given once or twice daily | Abdominal cramping, diarrhea, hypokalemia | In children: II–I |
| Rectal administration | ||
| Glycerin suppository | No adverse effects | |
| Bisacodyl suppository (10 mg): one-half to one suppository administered once or twice daily | Abdominal cramping, diarrhea, hypokalemia | |
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