Constipation in Childhood

Constipation in children is a common problem and is often accompanied by parental anxiety. It is typically characterised by infrequent bowel evacuations, large stools and difficult or painful evacuation. It accounts for some 25% of paediatric gastroenterologists' work and is also one of the 10 most common problems seen by general paediatricians.

It is important to define the terms used, as they inform diagnosis. The diagnosis in turn identifies the most appropriate management strategy. It is very important to make the diagnosis and start treatment. This is particularly because chronic constipation can lead to progressive faecal retention, rectal distension and loss of sensory and motor function.¹

On a practical note, when faced with the casual request of a laxative for a child, think carefully. It is recommended that the child be seen for a proper assessment and diagnosis. Reassurance and initiation of behaviour change (with regular unhurried toileting and rewarding successful toilet use) with the support of a health visitor and school nurse may be more effective and appropriate in the long-term.

Attempts have been made to define terms more precisely. There is something of a lack of consensus on the meaning of words used for common defaecation problems. It is important to distinguish the normal from the abnormal. Frequency of bowel action reduces on average from 4 x per day in early childhood to about 1 x per day by age 4, by which age most children (98%) are toilet trained.² Some terms regarded as imprecise, such as soiling and encopresis, have been replaced by the term incontinence.The following terms were recommended by the Paris Consensus on Childhood Constipation Terminology (PACCT) Group in 2005 and they inform the diagnostic criteria.³ In practice there are still children who have symptoms not adequately described by these terms.⁴

• Constipation in children, from whatever cause, is very common worldwide and 90-95% of constipation is functional. In a systematic review of the literature to assess prevalence, incidence and natural history in functional constipation:⁵
  • Prevalence ranged from 0.7% to 29.6%
  • Prevalence rates were similar in boys and girls
  • Age of highest prevalence could not be identified
  • Socio-economic factors were not found to be associated
  • Further studies using newer diagnostic criteria were called for
• Most children with constipation are developmentally normal. It is seen commonly in:
  • Infants at weaning
  • Toddlers acquiring toilet skills
  • School age
• Often psychosocial factors may be involved or suspected. They may precede or maintain the constipation.⁶

• History. In addition to general history (past medical history, school and social history and family history) the parent and child should be specifically questioned about the constipation. Parents can mistake incontinence for diarrhoea. In infants under 6 months, straining and crying for 10 minutes before passage of stools is caused by dyschezia (painful or difficult defaecation which resolves spontaneously) and may be mistaken for constipation. Specific questions should cover:
  • The frequency of defaecation
  • Consistency of stools - this may include use of the Bristol stool form chart⁷
  • Episodes of faecal incontinence
  • Pain on defaecation
  • Whether stools block the toilet
  • Any associated behaviour
  Any pain on defaecation is likely to lead to withholding. Toddlers and older children get better at withholding.
• Examination. This should include:
  • Palpation of the abdomen for faecal mass
  • Inspection for anal stenosis or ectopia
  • Looking for sacral abnormalities
  • Rectal examination is not routinely necessary or required
  • Routine radiography is not recommended

It is important to distinguish organic causes from the much more common functional causes. Many of the organic causes will present in the first few weeks of life.
The evaluation of constipation with or without soiling should begin with careful history and physical examination.

Organic causes of constipation

Organic causes of constipation and diagnosis, further investigations or tests include:¹⁰

• Anorectal malformations:
  • Physical examination. Careful inspection of the perineum in any baby with constipation:
    • Is the anus in correct position relative to vulva or scrotum?
    • Careful digital rectal examination with well-lubricated fifth finger is advocated by some (detect stricture, assess volume and hardness of rectal stool)⁴
• Anal fissure. This is common and associated with painful defaecation. Passage of blood and sentinel pile on the anterior anus are characteristic.⁴
• Rectal prolapse. This may be caused for example by chronic straining and constipation, disorders of sacral nerve innervation and chronic diarrhoea.⁴
• Hirschsprung's disease. This usually presents early (as delay in passing meconium, failure to thrive, etc) well inside the first month. However, rarely it can present late. Diagnosis is by:
  • Rectal biopsy - the test of choice
  • Anorectal manometry
  • Barium enema
• Neurenteric problems:
  • Colonic motility - the test of choice
  • Colonic transit
  • Possibly rectal biopsy
• Spinal cord problems:
  • Physical examination
  • Magnetic resonance imaging - the investigation of choice
  • Possible anorectal manometry
• Pelvic floor dyssynergia:
  • Anorectal manometry - the test of choice
• Metabolic or systemic disorders:
  • Hypothyroidism - thyroid function tests
  • Coeliac disease - tests for coeliac
  • Hypocalcaemia - calcium test
  • Cystic fibrosis - sweat test
• Toxic:
  • Lead levels, toxicology screen
• Cow's milk allergy:
  • Elimination diet
  • Allergy testing

Functional causes of constipation

Chronic constipation and other types of functional constipation:

• History and physical examination are most important in the assessment and further tests are rarely necessary
• Further investigations are recommended occasionally in chronic constipation and always in non-retentive faecal incontinence. Specifically:
  • Radiology (kidneys, ureter, bladder)
  • Colonic transit

History and examination are most important to make a diagnosis and should determine whether further investigations are required. The selection of investigations can be appreciated from the differential diagnoses above. Extensive investigations are not usually required.

This section is aimed at the management of functional constipation. The aims are to remove faecal impaction, restore bowel habit (with soft stools passed without pain), self toileting and passing of stools in appropriate places.

Note that:

• Infrequent defaecation increases the likelihood of pain on passage of hard stools, anal fissures, anal spasm and ultimately a learned response to withhold defaecation.
• Mild constipation may be relieved by increased fluid and dietary fibre intake. If necessary an osmotic or bulk-forming laxative may be prescribed. Stimulant laxatives can also be used but may precipitate colic, diarrhoea and overflow incontinence.^11,12
• Chronic obstruction may cause the rectum to enlarge to form a megarectum, which has impaired sensation and decreased contractility, resulting in soiling. If the bowel is impacted and cannot be cleared using oral laxatives, specialist referral for bowel cleansing solutions, suppositories, enemas or manual evacuation is recommended.¹³
• Regular bowel actions must then be established using dietary advice (fibre and fluid intake), regular laxatives (e.g. lactulose) and encouragement of a toileting pattern.
• Laxatives must be continued for many months and then gradually withdrawn. Relapses are common and should be treated early with increased doses of laxatives.¹¹
• Children and parents should be offered psychological counselling and support through the treatment process. Older children may also benefit from biofeedback training.¹³
• Very rarely children may requires enemas under sedation and even surgery to modify the anal sphincter.¹²

Available treatments

Evidence for effectiveness of treatments is weak.¹⁴ It is reasonable to base individual choices on the severity of symptoms, stool consistency, patient preference and cost. The lowest effective dose should be prescribed and reduced once symptoms improve. Oral preparations should be used whenever possible but short courses of rectal laxatives may be appropriate if oral treatments have failed or rapid relief of rectal loading is required. Rectal laxatives should be avoided if haemorrhoids or anal fissures are present.¹¹ Manual evacuation may be necessary if all pharmacological interventions fail.¹⁶

Medication

Laxatives can be divided into 4 main groups. An understanding of the basic mechanisms of action assists in the selection of appropriate drugs.¹⁶

• Osmotic laxatives:
  • Act by increasing the amount of water in the large bowel, e.g. lactulose, PEGs, rectal phosphates.
  • Variable time is needed to achieve their full effects. An adequate fluid intake is necessary to prevent dehydration and some preparations such as PEGs are administered with fluid to avoid this problem.
  • Phosphate enemas are useful for clearance of hard, impacted stools and for bowel evacuation before surgery and radiological or endoscopic investigations.
  • Osmotic laxatives must not be used in bowel obstruction and PEG should be avoided in patients with severe inflammatory conditions of the gastrointestinal tract, such as Crohn's disease or ulcerative colitis.¹¹
  • No randomised controlled trials (RCTs) comparing use with placebo.
  • No significant difference in lacitol versus lactulose in stool frequency or consistency.
  • More abdominal pain and flatulence with lactulose than lacitol has been reported.¹⁴
  • One RCT shows PEG more successful than lactulose with fewer adverse effects.¹⁷
• Stimulant laxatives:
  • Induce intestinal peristalsis by direct stimulation of the myenteric plexus, e.g. bisacodyl, docusate sodium, senna, dantron.¹⁶
  • Stimulant laxatives are popular because of their rapid effect but will often cause abdominal cramps.
  • Rectal preparations of stimulant laxatives are useful for prompt evacuation of impacted stools. Bisacodyl suppositories are used to evacuate soft stools from the lower rectum. Glycerol suppositories will eliminate soft or hard stools from the lower rectum and docusate sodium enemas will clear faeces from the upper rectum.¹¹
  • Stimulant laxatives must be avoided in bowel obstruction as they may lead to perforation.
  • Long-term use of high doses can cause diarrhoea with significant fluid and electrolyte imbalances; however prolonged therapy is sometimes necessary.¹¹
  • All preparations containing dantron, such as co-danthramer and co-danthrusate should be restricted to terminally ill patients due to concerns regarding genotoxicity.¹¹
  • Cochrane review shows insufficient evidence for efficacy of stimulant laxatives¹⁸
  • No placebo RCTs of the effects of stimulant laxatives in children were found¹⁴
• Bulk-forming laxatives:
  • Bulk-forming laxatives retain water within stools and increase faecal mass, thus stimulating peristalsis, e.g. ispaghula, methylcellulose.
  • An adequate water intake is necessary to avoid worsening constipation and intestinal obstruction.
  • Full effects may take several days so they are inappropriate for acute relief of constipation.¹¹
  • Bulk-forming laxatives are useful in the management of patients with small, hard stools and those with stomas, haemorrhoids, anal fissures.
  • Patients may complain of flatulence, bloating and abdominal distension but side-effects usually settle with continued use.¹¹
• Faecal softeners:
  • Faecal softeners act by decreasing the surface tension of stools and facilitating infiltration of intestinal fluid, e.g. arachis oil, docusate sodium (which has stool-softening properties in addition to its stimulant effects).¹¹
  • These drugs are useful for oral administration in the management of haemorrhoids and anal fissures as they will soften and lubricate faecal material.
  • Arachis oil enemas are also useful in the management of patients with hard, impacted stools. Liquid paraffin is not recommended as it can cause anal seepage and irritation, lipoid pneumonia and malabsorption of fat-soluble vitamins.¹¹
• Drugs in development:
  • Recent work has focused on the development of specific 5-HT4 receptor agonists. In contrast to conventional laxatives, which act through luminal mechanisms, these prokinetic agents are absorbed in the small intestine and systemically stimulate intestinal peristalsis.
  • Tegasarod was licensed in the United States but had to be removed due to safety concerns.
  • A similar drug, prucalopride, is currently undergoing clinical trials.^19,20,21
  • Subcutaneous methylnaltrexone is undergoing trials for treating opioid-induced constipation in patients with advanced illness, with good results.²²

Other measures

• Biofeedback and psychological interventions:
  • Evidence for benefit is lacking.¹⁴
  • 50% of constipated children contract rather than relax the external sphincter during defaecation attempts and although biofeedback can change this behaviour, there is no additional outcome benefit over conventional long-term and adequate laxative treatments.^23,24
  • Behaviour modification used in addition to laxatives does improve rates of soiling at 3 and 12 months. Rewarding successful toilet use is better than rewarding 'staying clean'.¹⁴
• Increasing dietary fibre:
  • Evidence is lacking.¹⁴
  • One double-blind, randomised crossover study reports benefit from fibre and suggests continued use in the diet of constipated children with or without encopresis.²⁵

Indications for referral

Specialist assessment is indicated if:

• Organic cause suspected
• Treatment unsuccessful
• Management is complex

When an organic cause is suspected, the GP can arrange for initial tests (such as inflammatory markers, thyroid function, calcium, tests for coeliac disease). Some specialists measure colonic transit time to differentiate:

• Soiling with normal transit time from
• Constipation and delayed transit time (worse outcomes)

Surgery is required rarely for the most severe cases of chronic constipation and overflow soiling. It can be important in intractable cases.⁴ Botulinum toxin has been used for short aganglionic segments of bowel and to provide temporary weakening of the sphincter.⁴

Failure to correct functional constipation may lead to problems. For example, the following may arise:

• Faecal impaction
• Chronic constipation
• Megacolon (may predispose to, or result from, constipation)
• Rectal prolapse
• Anal fissure
• Faecal soiling
• Psychological effects

Long-term follow-up studies of children under age 5 referred to a specialist clinic showed 50% recovery within 1 year and 65-70% recovery within 2 years, with the remaining 30% or so requiring long-term laxatives, or continuing to soil.⁶ In another study, 30% of children continued to have severe constipation beyond puberty.²⁶ Obviously results from earlier treatment of less severe cases in general practice should be better than this.