Paediatrics chapters
Constipation in children
Why most childhood constipation is functional stool withholding, how to spot organic causes such as Hirschsprung disease, hypothyroidism and spinal problems, and how to treat with clean-out, laxatives, diet and toilet training.
- Constipation is infrequent (two or fewer a week), hard or painful stools, often with soiling; over 90% is functional, driven by painful defecation and voluntary withholding, typically starting at weaning, toilet training or school entry.
- Red flags for an organic cause: onset from birth, meconium delayed beyond 48 hours, abdominal distension, vomiting, poor growth, empty rectum with tight sphincter (Hirschsprung), abnormal lower-limb neurology or sacral lesions (spinal cord), and features of hypothyroidism.
- Treat with education, disimpaction, then months of maintenance laxative (PEG or lactulose), fibre and fluid, and regular toilet sitting after meals with praise; relapse is common if treatment stops early.
On this page
Overview
Constipation is very common in children and causes much distress through pain, soiling and family conflict. In nearly all cases it is functional: the child holds stool back after a painful motion, the rectum stretches, and a vicious cycle begins. The task is to exclude organic causes with a careful history and examination (not routine tests), then commit the family to months of treatment.
Definitions
| Term | Meaning |
|---|---|
| Constipation (Nelson) | Stools no more than twice a week, or hard, pellet-like stools, lasting 2 weeks or longer |
| Constipation (Akbar) | Passage of bulky or hard stool with difficulty at infrequent intervals |
| Functional constipation | Constipation without an organic cause, with voluntary withholding and large, painful stools |
| Encopresis | Repeated passage of stool in inappropriate places (underwear) after 4 years of age |
| Soiling / overflow | Involuntary leakage of liquid stool around a faecal mass; often mistaken for diarrhoea |
Normal frequency falls from more than four stools a day in early infancy to about one a day by 4 years (Nelson).
Parents often report "diarrhoea" when the child is actually soiling liquid stool leaking around an impacted mass. Examine the abdomen and rectum.
Aetiology
Functional (over 90%)
Nelson notes about 95% of children referred for soiling have no underlying disease.
- Painful defecation (hard stool, anal fissure) leads to withholding
- Low-fibre diet, low fluid intake, excess cow's milk (toddler diet)
- Developmental triggers: weaning to solids, toilet training, starting school (no private toilets)
- Slow colonic transit (constitutional or familial)
- Psychological stress, avoiding the toilet
#### The withholding cycle
Painful stool → child holds back (retentive posturing: stiff legs, crossed legs, standing on tiptoe) → stool stays in rectum, water is absorbed, stool gets harder and larger → rectum stretches, sensation falls → next stool even more painful → soiling as liquid stool leaks around the mass.
"Hurts, Holds, Hardens, Hurts more" = the withholding cycle.
Organic causes
| Group | Causes |
|---|---|
| Anatomical | Hirschsprung disease, anal stenosis, anteriorly displaced anus, imperforate anus (after repair), strictures |
| Neurological | Spina bifida / meningomyelocele, tethered cord, sacral tumours, cerebral palsy, hypotonia |
| Endocrine / metabolic | Hypothyroidism, diabetes mellitus |
| Gut | Cystic fibrosis (meconium ileus equivalent), coeliac disease, cow's milk protein intolerance |
| Drugs | Opioids, anticholinergics, phenothiazines, antidepressants, iron, loperamide |
| Other | Muscular dystrophy, lead poisoning, infant botulism, developmental delay, autism |
Clinical features
History
- Age of onset: from birth suggests organic disease; after weaning or toilet training suggests functional
- Meconium passed within 48 hours? Delay points to Hirschsprung disease or cystic fibrosis
- Stool frequency, size (large stools that block the toilet), hardness, pain, blood streaks (fissure)
- Withholding behaviour, soiling, abdominal pain, poor appetite
- Diet (fibre, fluid, milk), drugs, urinary symptoms (enuresis, UTI often coexist)
- Growth, development, family and social stresses
Examination
- Growth (weight, height)
- Abdomen: distension, palpable faecal mass in the left lower quadrant or suprapubic area
- Perianal inspection: anal position, fissures, skin tags, soiling, sores
- Lower back: sacral dimple, hairy tuft, lipoma, sinus (spinal dysraphism)
- Neurology: lower-limb tone, reflexes, anal wink, cremasteric reflex
- Digital rectal examination (when needed): sphincter tone, rectal size, stool
Functional constipation versus Hirschsprung disease
| Feature | Functional constipation | Hirschsprung disease |
|---|---|---|
| Onset | After weaning / toilet training | From birth |
| Meconium | Normal | Delayed (over 24 to 48 hours) |
| Stool size | Very large | Small, ribbon-like; may have explosive stools |
| Soiling / encopresis | Common | Rare |
| Withholding behaviour | Common | Rare |
| Abdominal distension | Mild or absent | Marked |
| Growth | Normal | Poor |
| Rectal examination | Rectum full of stool, normal or lax tone | Tight sphincter, empty rectum, explosive gush on withdrawal |
| Enterocolitis risk | No | Yes (fever, foul diarrhoea, distension) |
| Barium enema | Dilated rectum down to anus | Narrow distal segment, dilated proximal colon (transition zone) |
| Biopsy | Ganglion cells present | Ganglion cells absent, hypertrophied nerve fibres |
Within the first day of life, only about 6% of infants with Hirschsprung disease have passed meconium, against about 95% of healthy term babies (Nelson).
Red flags for organic disease
- Onset at birth or in the first month; delayed meconium
- Abdominal distension, bilious vomiting, failure to thrive
- Ribbon stools, empty rectum with tight sphincter
- Abnormal lower-limb neurology, absent anal wink, sacral abnormality, bladder problems
- Features of hypothyroidism (poor growth, bradycardia, coarse features, prolonged neonatal jaundice)
- Abnormal anal position, anal stenosis
- Blood in stool other than fissure streaks; weight loss
Investigations
- Functional constipation needs no tests: diagnosis is clinical. A plain abdominal X-ray is not required (Nelson); it may help show impaction to a family or in an obese child who cannot be examined.
| Suspicion | Test |
|---|---|
| Hirschsprung disease | Rectal suction biopsy (absent ganglion cells: diagnostic); anorectal manometry (no relaxation of the internal sphincter on rectal distension); barium enema (transition zone) |
| Hypothyroidism | TSH, T4 |
| Coeliac disease | Anti-tTG with total IgA |
| Cystic fibrosis | Sweat chloride |
| Spinal dysraphism, tethered cord | MRI spine |
| Lead poisoning | Blood lead |
Differential diagnosis of chronic or severe constipation
| Condition | Clue |
|---|---|
| Hirschsprung disease | From birth, delayed meconium, distension, empty rectum |
| Spinal cord lesion | Sacral dimple or tuft, weak legs, bladder problems, lax anus |
| Hypothyroidism | Poor growth, bradycardia, developmental delay |
| Anal stenosis / anterior anus | Seen on inspection; pain from birth |
| Cystic fibrosis | Meconium ileus history, chest infections, poor growth |
| Coeliac disease | Poor growth, anaemia, distension |
| Drug effect | Opioids, anticholinergics, iron |
| Infant botulism | Constipation then weakness, poor feeding, ptosis |
Management
1. Education
Explain the withholding cycle, remove blame (soiling is not deliberate), and warn that treatment takes 6 to 24 months (Nelson). Good adherence predicts success.
2. Disimpaction (clean-out)
- Needed if there is a faecal mass.
- Oral route preferred in most children: high-dose polyethylene glycol (PEG) over a few days; alternatives include mineral oil and stimulant laxatives.
- Enemas or suppositories if oral treatment fails or a rapid clean-out is needed (glycerin suppositories in infants). Phosphate enemas can cause hyperphosphataemia and hypocalcaemia, especially in young children, Hirschsprung disease or renal impairment.
3. Maintenance
| Measure | Detail |
|---|---|
| Osmotic laxatives | Polyethylene glycol (well tolerated, palatable) or lactulose/sorbitol; milk of magnesia |
| Lubricants | Mineral (liquid paraffin) oil: if aspirated it causes lipoid pneumonia, so it is unsuitable for children who may aspirate |
| Stimulants | Senna or bisacodyl for short periods in severe cases |
| Duration | Continue for months, until a regular soft-stool habit is established; then taper slowly |
Use a non-habit-forming, safe, palatable softener and adjust the dose until stools are soft and regular without pain.
4. Diet
- Fibre: Nelson's daily target is 10 g plus age in years (a 6-year-old needs about 16 g a day); fruit, vegetables, whole wheat, bran.
- Fluids: enough water; juices with sorbitol (pear, prune, apple) soften stool.
- Limit excess cow's milk in toddlers.
A 6-year-old child.
Fibre target = 10 g + 6 = 16 g per day
5. Behaviour and toilet training
- Sit on the toilet for 5 to 10 minutes after meals (use the gastrocolic reflex), 3 to 4 times a day at first.
- Feet supported on a footstool, leaning slightly forward.
- Star chart and praise for sitting and taking medicine; no punishment or shaming.
- Stool diary.
- Psychological help if resistant or behaviour problems.
6. Treat complications and causes
- Anal fissure: stool softening, local care.
- Hirschsprung disease: surgery (resection of the aganglionic segment); treat enterocolitis with fluids and antibiotics.
- Hypothyroidism: thyroxine.
Stopping laxatives as soon as the child improves is the commonest reason for relapse. The stretched rectum needs months to recover tone and sensation.
Complications
- Anal fissure and rectal bleeding
- Faecal soiling/encopresis, low self-esteem, social withdrawal, school problems
- Urinary problems: UTI, enuresis (full rectum presses on the bladder)
- Abdominal pain, poor appetite
- Hirschsprung enterocolitis (organic cause, can be fatal)
Prognosis, prevention and follow-up
- With good management, half to two thirds of children recover completely and come off medication (Nelson); about one in five fails, usually from poor adherence and re-impaction.
- Starting treatment early in younger children gives the best results.
- Prevention: enough fibre and fluid from weaning, avoid excess milk, regular toilet routine from an early age, treat painful stools and fissures early.
- Follow-up regularly to adjust laxative dose, review the stool diary and support the family.
Expect: the definition and that most constipation is functional with withholding; encopresis after 4 years with overflow soiling mistaken for diarrhoea; red flags (onset at birth, delayed meconium, distension, poor growth, abnormal neurology or sacrum); functional constipation versus Hirschsprung disease (stool size, soiling, rectal examination, rectal biopsy showing absent ganglion cells, manometry); no routine X-ray; disimpaction then maintenance with PEG or lactulose; fibre 10 g plus age; toilet sitting after meals; and the long duration of treatment.
Quick revision
- Two or fewer stools a week or hard pellets for 2 weeks or more.
- Over 90% functional: pain → withholding → hard stool → soiling.
- Encopresis: soiling after age 4; overflow looks like diarrhoea.
- Hirschsprung: from birth, delayed meconium, distension, empty rectum, no soiling; suction biopsy.
- Other organic: hypothyroidism, spinal cord lesions, CF, coeliac, drugs, anal anomalies.
- No tests for functional constipation; clinical diagnosis.
- Clean-out, then PEG or lactulose for months; fibre 10 g + age; toilet after meals.
- Relapse common if laxatives stop early.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Does every constipated child need an abdominal X-ray?
No. Functional constipation is diagnosed from the history and examination; an X-ray adds little and is not routinely needed.
How can I tell Hirschsprung disease from functional constipation?
Hirschsprung disease starts at birth with delayed meconium, distension and an empty rectum with a tight sphincter, and soiling is rare; functional constipation starts later with very large stools, a full rectum and soiling.
Why does a constipated child soil?
Liquid stool from higher up leaks around the hard mass in a stretched rectum whose sensation is reduced, so the child often does not feel it coming.
How long should laxatives continue?
Usually for many months, until a regular soft-stool habit is established, and then they are tapered slowly to prevent relapse.