Constipation

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7.13 Constipation

Bruce Fasher

Essentials

1 It is important to understand the physiology and development of gut transit to recognise the normal (often regarded as abnormal).
2 Constipation is a common reason for children to present to EDs with abdominal pain.
3 Management depends on the child’s age and whether the problem is acute or chronic.
4 The patient’s and parents’ real concerns need to be acknowledged.
5 Issues to be addressed include:

• natural history;
• the aims of treatment (empty the bowel and establish pharmacological rhythm and then wean to biological rhythm);
• the likely duration of treatment;
• the anticipated setbacks;
• the need for a coordinator clinician (normally unavailable in an ED).

6 Treat from the top, once at night and titrate the dose according to the response. Avoid treatment per rectum if at all possible, to draw attention away from any anal obsession to achieve bowel actions.
7 Be able to refer to a resource who is known to be interested in managing the condition and to ensure appropriate ongoing review and support.

Introduction

Constipation in childhood engenders in clinicians unwarranted anxieties about management. Defining terms and understanding normal physiology and its variants, the frequent blurring in paediatric medicine between physical and emotional factors and their impact on normal development along with evidence-based data can provide the clinician with an algorithm for management.

Management varies according to age and whether constipation is acute or chronic. The emergency department (ED) is a difficult place from which to manage constipation, especially chronic constipation, for success requires ongoing maintenance therapy and contact with a committed and interested clinician. This is best achieved through the child’s local doctor, with input from a sympathetic paediatrician in difficult cases if deemed appropriate.1,2

Definitions

Constipation is delay or difficulty in defecation, sufficient to cause significant distress.
Encopresis is the passage of a normal stool in an abnormal place.
Soiling is the frequent involuntary passage of loose or semi-loose stools in clothing. This is usually overflow incontinence as the liquid stool escapes around an impacted rectal faecolith.

Pathophysiology

The rectum and anal canal have two tasks, to store faeces temporarily and to evacuate at a socially convenient time. The distending rectum evokes a wave of contraction with inhibition of the smooth muscle tone of the internal anal sphincter, resulting in a sensation of the urge to defecate. An urgent desire to defecate occurs as the stool stretches the sensitive zone of the upper anal canal. This urge is overcome by the voluntary contraction of the external sphincter and the levator ani muscles. Eventually the rectum habituates to the stimulus of the enlarging faecal mass and the urge to defecate subsides. With time this retentive pattern can become automatic.

It is understandable, therefore, that the child who is afraid to use the non-private, wet, smelly school lavatory, and allows his rectum occasionally to overcome the external sphincter, as he is relieved to arrive home, albeit with ‘poo in the pants’ – is really a normal variant rather than true encopresis.

There is a wide variation of physiology and normal development as can be seen in the age range of successful potty training. To produce a stool at will is one of the child’s first major achievements and most gain satisfaction from framing their success in a pot. If too much persuasion is provided, especially if full control has never been attained, the child’s profound disappointments are compounded by disapproval and hostility from the parents. Like most adults, most children seek solitude to defecate.

Management basics

Be interested. The patient has often been pushed from pillar to post, with a quick fix, and reviewed in 3 months. Recognise that the parents and the patient have a concern, which can be the cause of major family dysfunction.
Endeavour to treat from the top, orally, rather than continue to direct attention to the rectum and anus with suppositories and enemas. The exception is when a fissure needs managing with ointment or Xylocaine ointment if defecation can be anticipated.
Develop a pharmacological armamentarium of stool softeners or osmotic aperients. Stimulants (e.g. senna) may cause abdominal discomfort with colic in infants.
Be aware that ongoing management by a single interested clinician is desirable as the constipation will often relapse, and gains are often small (three steps forward, two steps back).
This makes constipation difficult to manage in EDs. Such departments need to have appropriate and willing referral resources. Outpatient appointments rarely work for the same reasons – difficulties with continuity of care and the ability to be seen relatively urgently (albeit that encouragement with management, behavioural modification and aperient dose titration is often all that is necessary and can often be done by phone by the interested clinician).
The significant risk of relapse dictates that a period of maintenance therapy is necessary before weaning off medications. It might be appropriate to let the patient and family know that if it has taken 2 years to arrive at this stage it is highly likely it will take 2 years or so to regain the rectum’s natural motility and sensitivity.

Constipation in babies

Never again in life will the stooling pattern, and indeed the stools, be so closely examined as in the period of nappies being changed prior to toilet training. Straining at stool is often marked and then misconstrued as constipation whereas it is a simple reflection of the urge to defecate sensation. Plantar flexion of the toes is a similarly objective sign (at all ages).

Breast-fed infants may pass a stool after each feed or as infrequently as once every few weeks. As long as the stool is of normal quality (often referred to as scrambled eggs) and of great volume there is no reason for concern. For a couple of days prior to defecation the infant may be, not unreasonably, somewhat unsettled.

Just weaned, bottle-fed infants may produce dry, hard stools with difficulty and sometimes traces of fresh blood. Attention to water intake, perhaps addition of extra sugar (brown sugar is better) or sorbitol (1–3 mL kg−1 noct.) will help soften the stool. Formula switching is usually unproductive, although it is recognised that some forms of cows’ milk intolerance may present with persistent constipation.

Should constipation persist and the clinician is confident that mother’s description is of constipation, red flags should alert other considerations.

Fever, vomiting, bloody diarrhoea, failure to thrive, anal stenosis, abdominal distension, history of delayed passage of meconium, polydipsia or polyuria should prompt a search for physical causes.

Conditions to consider are listed in Table 7.13.1.

Table 7.13.1 Conditions possibly causing persistent constipation

• Anal anomalies (stenosis, stricter, malposition)
• Spinal anomalies (spinal dysraphism, sacral agenesis)
• Hirschprung’s disease
• Hypothyroidism
• Metabolic – hypercalcaemia, hypokalaemia
• Coeliac disease
• Cows’ milk intolerance
• Lead poisoning
• Intellectual impairment
• Child abuse
• Cystic fibrosis
• Dietary – inadequate roughage, excessive cows’ milk intake
• Psychogenic – parent-child and environment issues
• Drug related – anticholinergic, sympathomimetics, codeine

Acute constipation

Acute constipation often occurs after febrile illnesses, change in diet or environment, especially when intake has been low (e.g. low post-operatively). A fissure in ano, usually from the passage of a hard faecolith, may cause pain, sphincter spasm, withholding and the start of a vicious cycle leading to chronic constipation with megacolon and overflow incontinence. Also consider the management of a fissure-in-ano which may be hiding in the anal skin folds.

Most acute constipation resolves spontaneously but given the risk of chronic constipation, especially if there has been a previous tendency to constipation, it may be prudent to commence gentle oral therapy early.

Chronic constipation

Chronic constipation is defined as persistent delay and difficulty in defecation often associated with soiling (overflow incontinence). Symptoms may be temporarily relieved by laxatives but relapse rapidly. This is why the ED is not the ideal place for long-term management, but may offer acute intervention for immediate relieve of unpleasant symptoms and to gain the family’s confidence by explaining management and natural history.

These children usually present in the school-age group. There may be a history of fissure, pain and withholding then ongoing constipation for months or years. The colon, rectum and upper anal canal become loaded with faeces, insensitive and hypotonic. Soiling develops with loose faeces escaping around an inspissated hard faecolith. Faeces are often palpable per abdomen. Social rejection in the class, due to the malodorous state, is often the first impetus for the patient themselves to seek cure. This, with loss of ability to defecate at will, takes a toll on the child’s emotional stability. They have often undergone multiple management regimens from dietary manipulation to manual disimpaction, delivered by a variety of healthcare workers.

Investigations

When there is doubt regarding the diagnosis, a plain abdominal X-ray is useful to demonstrate faecal loading. Demonstration of the X-ray findings to the parents may be additionally useful to aid adherence to prolonged therapeutic strategies.

Management

The management of acute versus chronic constipation varies mainly in nuance and the extent and duration of treatment.

The aim of treatment is that in gaining the family’s confidence the clinician recognises that there is a very real concern, and a plan can be instituted to:

Exclude physical treatable causes with careful history, examination and investigations as warranted.
Empty the rectum, preferably ‘from the top’ i.e. through oral agents rather than per rectum.
Establish a pharmacological bowel rhythm and pattern, which may need support for several years.
Allow the enlarged rectum/colon to re-establish its own inherent physiological bowel pattern and tone and to regain its normal sensation.
Continue maintenance for some time before considering slowly weaning off pharmaceuticals.

This will involve:

• Enthusiasm on part of managing clinicians.
• Non-punitive behaviour on part of the parents.
• Adjunctive behavioural modification interventions with achievable goals.
• Acknowledging the need for patience, determination and resolution as the most chronic cases will take years to resolve.
• Stool lubricants, paraffin oil, the taste of which has been well masked in Australia by Parachoc, using a nocturnal dose starting at 10 mL and titrating dose according to response (not recommended less than 1 year old due to possible aspiration pneumonia).
• Osmotic laxative, lactulose or sorbitol, initially 3 mL kg−1 noct. as a 70% solution, titrating dose according to response.
• Stimulants, senna starting at 2.5 mL noct. titrating dose according to response (side effects are possible colic, and if used in combination with a lubricant it may just make the faecolith spin around).
• Good results have been achieved using sachets (according to the directions) of Macrogol 3350 which is available in several palatable commercial presentations. The Macrogol 3350 induces a laxative effect by osmosis, is virtually unchanged and unabsorbed in the gut and has no known pharmacological activity. Electrolytes are present in the formulation, realising virtually no net loss of sodium, potassium or water.

Only should oral therapy be inadequate or if a large impacted stool in rectum is causing significant acute distress: treatment from below may be necessary.

• Suppositories of glycerin may be helpful, especially in acute constipation.
• Microlax enemas are also helpful in the acute situation.
• Phosphate enemas (these should be avoided in children less than 2 years old; persistent use may cause hyperphosphataemia, hypocalcaemia and tetany).
• Enemas, soap and water (tap water and magnesium have potential toxicity).

Disimpaction of an obstinate rectal faecolith may require:

• Polyethylene glycol – electrolyte solution lavage, 25 mL kg−1 hr−1 (to 1000 mL hr−1 by nasogastric tube); causing nausea, bloating, cramps, aspiration pneumonia. This will require the child to be admitted to hospital.
• Manual disimpaction under general anaesthesia.
• There is no evidence-based medicine to suggest the success or otherwise of anal dilatation (Lord’s procedure), and some consider permanent external sphincter damage may occur.

Maintenance therapy

Focuses on the prevention of recurrence and should be instituted straight after successful disimpaction or for the child presenting without disimpaction. This involves, as above, dietary interventions, behavioural modification, laxatives, patience and enthusiasm.

Dietary changes

Those commonly advised include increased fluid intake, absorbable and non-absorbable carbohydrate, (sorbitol is found in prune, pear and apple juice). No randomised control study confirms the benefit of this. Forceful implementation would then seem undesirable.

Controversies and future directions

The role of serotonin type 4 receptors in the neurochemical basis of peristalsis may provide a more logical pharmaceutical approach to the future management of constipation.

References

1 Clayden G.S. Constipation and soiling in childhood. Problems of childhood. London: BMA; 1976.

2 Baker S.S. Constipation in infants and children: Evaluation and treatment. J Pediatr Gastroenterol Nutr. 1999;29(5):612-626.

Further reading

Liptak G.S. Constipation. In: Meyer, et al. Evidence-based paediatrics and child health. London: British Medical Journal Books, 2000.

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