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Childhood constipation: looking at the options

WA McCallion
BSc MD FRCSPaed
Consultant Paediatric Surgeon
Royal Belfast Hospital for Sick Children

E:bill.mccallion@royalhospitals.n-i.nhs.uk

Constipation, defined as the infrequent passage of stool associated with abdominal pain/distension or anal pain, is endemic in the developed world. For a condition that on the surface appears to be so innocuous, it creates mayhem in the family home. Consultations with constipated children and their parents are often lengthy, but with successful management there will be few patients (and parents) who are more grateful.

Constipation may be classified according to ­aetiology:

  • Functional constipation.
  • Organic anorectal pathology.
  • Colonic motility disorders.

Functional constipation
Functional constipation is by far the most common and usually begins in early childhood following an episode of painful defecation. The child then associates defecation with pain and, in order to avoid the painful stimulus, begins stool-holding behaviour. This is usually associated with abdominal cramps as the colon tries to propel the ever-enlarging faecal bolus. Eventually the stool is passed, causing great discomfort, and often splitting the sensitive skin at the anal verge.

The resulting fissure produces a few spots of blood on the toilet paper or nappy, which greatly increases parental anxiety. At this stage it is common for suppositories or enemas to be prescribed, but they trigger further anal pain and merely accentuate the child's anxieties. The earlier that treatment with oral laxative is instituted, the more quickly the child will disassociate defecation from pain. Left untreated, the rectum may become chronically distended with stool over months or years (see Figure 1). As a result, rectal sensation may be lost so that the child can no longer differentiate between a full and an empty rectum. Overflow soiling ensues, adding to the behavioural problems.

[[NIP10_fig1_38]]

Organic anorectal pathology
Congenital anorectal pathology, such as Hirsch­sprung's disease (congenital aganglionosis of the rectum and colon) or low anorectal malformations, usually presents in the neonatal period. It is worth remembering that low anorectal malformations can be missed during the hospital "baby check", making examination of the perineum essential in young infants presenting with defecation problems. This is particularly true for females as the rectum may open anywhere in the perineum from the external anal sphincter to the vestibule (see Figure 2). Occasionally, Hirschsprung's disease presents in older infants or children as constipation, in which case abdominal distension and failure to thrive are key symptoms. A rectal biopsy is required to establish this diagnosis. Cystic fibrosis may present similarly due to the inability to propel the abnormally viscid residue. Acquired perianal pathology may trigger childhood constipation. Perianal cellulitis secondary to streptococcal ­infection is not uncommon and responds well to oral penicillin (see Figure 3). Anal fissures in older children may be a ­manifestation of Crohn's ­disease, but ­clinicians must always bear in mind the possibility of child sexual abuse.

[[NIP10_fig2_38]]

[[NIP10_fig3_39]]

Colonic motility disorders
Motility disorders of the colon and rectum are uncommon but well-recognised causes of intractable constipation during childhood.(1) Primary motility disorders are a rather ill-defined group of conditions that may be due to visceral neuropathy or myopathy. Rarely, colonic dysmotility may be secondary to hypercalcaemia, hypothyroidism or autoimmune disease.

Treatment
Laxatives form the mainstay of treatment for childhood functional constipation. While lack of dietary fibre is usually implicated, the addition of fibre alone is seldom sufficient to regain normal colorectal function. Management begins with emptying the colon and rectum. This is most easily achieved with a high-dose stimulant laxative for 1-3 days. This will be a difficult period for the child and parents, and it is often worthwhile suggesting that, if appropriate, the parent(s) takes time off work to give the child maximal attention. After the child has been "cleared out", a maintenance dose of laxative is commenced. The type of laxative used (softener versus stimulant) will have to be determined on a trial-and-error basis, but very often stool softeners are insufficient. Giving parents the responsibility for titrating the dose of laxative cannot be overemphasised. The aim is for their child to have a daily bowel motion (using a dose of laxative determined by the parent) rather than simply giving him/her a set amount of medication dictated by the doctor. Most children with functional constipation require long-term treatment.(2) There is rarely a "short, sharp" cure. More than half will require laxatives for at least a year. Enemas are not well tolerated by children with functional constipation and for the most part should be avoided. Given that painful defecation has usually been the trigger, administration of the enema will be a struggle for both child and parent.

Children with intractable constipation should be referred to a paediatrician. Clearly, if there is an underlying cause such as Hirschsprung's disease, early referral is appropriate. Some children with functional constipation develop severe behavioural problems, and input from a child psychologist can be invaluable. It goes without saying, though, that the latter must go hand in hand with appropriate laxative treatment rather than being seen as a panacea for childhood constipation. Children with poor rectal sensation may benefit from biofeedback therapy.(3) This involves inflation of a rectal balloon: with time, the child learns to differentiate between the inflated and deflated balloon. This mode of treatment is extremely time-consuming, and its success may be related more to the enthusiasm of the clinician (or nurse specialist) than the technique itself. Older children with colonic motility disorders can often be encouraged to accept colonic lavage, but that too is something best managed through specialist centres.

Only rarely is surgical intervention appropriate. Stretching of the external anal sphincter under general anaesthesia should not be considered. Biopsy of the rectal mucosa to exclude Hirschsprung's disease requires referral to a paediatric surgeon or paediatric gastroenterologist. Antegrade colonic enemas may be used if there is a long-term need for lavage in children with colonic dysmotility. With this technique, enema fluid is delivered directly into the colon usually via the appendix, which has been brought out on the abdominal wall as a small continent stoma. Colostomy should be considered as a last resort and, thankfully, is very rarely required.

[[NIP10_pp_39]]

References

  1. Wheatly JM, Hutson JM, Chow CW, Oliver M, Hurley MR. Slow transit constipation in childhhod. J Pediatr Surg 1999;34:829-32.
  2. Loening-Baucke V. Chronic ­constipation in children. Gastroenterology 1993;105:1557-64.
  3. Berquist WE. Biofeedback therapy for anorectal disorders in children. Semin Pediatr Surg 1995;4:48-53.

Resources
Chronic ­constipation and encopresis in ­children
W:http://hsc.virginia.edu/cmc/tutorials/constipation/encopre.htm

Constipation in children
W:www.niddk.nih.gov/health/digest/summary/conchild