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Constipation

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A 7-year-old boy is brought in by his mother with a six-month history of faecal soiling.

He opens his bowels every other day.  Sometimes these are giant snakes of poo and other days, they are small pellets.  He soils his pants 5-6 times per week, usually in the daytime and is being bullied at school.

He complains of tummy pain every day. His parents have tried multiple short courses of laxatives and are convinced they don’t work. 

He has a palpable mass in his left iliac fossa that you can indent.

He has constipation.

What should you do next?

Although you may groan a little inside, thinking, ‘not another child with constipation’, just remember that up to one-third of these children will develop chronic constipation, leading to significant psychosocial consequences. Opportunities for early intervention are often ignored, yet an extra five minutes with these patients can make a great deal of difference to their long-term outcomes.

What’s important in the history?

  • Frequency of stool
  • Consistency – show the child a Bristol Chart
  • Timing and onset of constipation
  • Symptoms associated with defaecation, i.e. distress on stooling, bleeding associated with hard stool, straining
  • Overflow soiling
  • Abdominal pain
  • Precipitating factors, i.e. fissures, change of diet, infections, medications
  • Any neurological problems in the legs?
  • Diet and fluid intake – any changes in infant formula or weaning?
  • Previous treatments tried
  • Past medical history: the passage of meconium (should be within 48 hrs after birth); previous episodes of constipation; previous anal fissure; growth and general wellbeing; family/social history.
Bristol stool chart - an invaluable tool for talking about constipation
The Bristol Stool chart

What should I look for in the examination?

  • Plot growth
  • Abdominal examination
  • Perianal exam – appearance, position, patency, fissures
  • Spine – scoliosis
  • The skin overlying the spine – discoloured/sinus/hairy patch/central pit
  • Gluteal muscles – is there asymmetry?
  • Gait
  • Tone and strength in lower limbs
  • (+ reflexes if there are features on the exam that suggest neurological impairment)
  • No PR! A PR exam should only be undertaken by a doctor competent to interpret features of anatomical abnormalities or Hirschsprung’s disease, e.g. paediatric surgeons.

What are the red flags?

  • Constipation from early infancy
  • Delay in meconium >48hrs
  • Ribbon stools
  • Weakness in legs
  • Abdo distension and vomiting
  • Abnormal appearance of anus
  • Asymmetry/flattening of gluteals
  • Sacral agenesis
  • Skin changes overlying the spine
  • Deformity of lower limbs – talipes
  • Abnormal neuromuscular signs
  • Abnormal reflexes

It may seem mundane, but successfully managing constipation can make a massive difference in the lives of families. Although it’s all about faeces, it can lead to other issues, including pain and social embarrassment. Time spent managing this can have a knock-on effect on the whole family, as well as the patient.

What is normal?

Normal bowel movements vary with age:

AgeStools per dayMouth to rectum time (hrs)
<2 years<216
<3 months2 to 38.5
0-1 week4-

What happens to poo?

As stool goes around the colon and out to the rectum, water is reabsorbed. So by the end, it will be smaller and harder than it was when it was at the appendix (which is why colostomy bags initially have a watery output). Hard poo is sore to pass, so children often don’t want to pass it at all. Therefore it collects and stays in the bowel longer, getting more and more impacted. If stools take a longer time to pass through the colon, they will become harder and drier. So the treatment is based on adding water and getting things moving.

There are three periods when children are prone to developing constipation: introducing solids; toilet training, and starting school. These all have the potential for defecation to be an unpleasant experience, prompting the child to consciously or subconsciously avoid repeating it.

This painful defecation can then lead to avoidance of defecation which results in stool accumulation in the rectum. The stool becomes harder and therefore more painful to pass. Chronic rectal distension leads to relaxation of the internal anal sphincter and semi-solid stool leaks or soiling. Finally, the rectum is unable to generate enough pressure to pass stool.

What causes constipation?

Causes can be split into functional and organic.

Functional constipation
This is an umbrella term for difficult, infrequent, or incomplete defecation with no structural or biochemical cause. It accounts for 95% of constipation.

Organic constipation
This is constipation associated with an organic condition which accounts for 5% of constipation. Organic causes are anatomic malformations; metabolic; gastrointestinal; neurological; connective tissue disorders; drugs; miscellaneous.

If functional accounts for 95% then we should know more about it – what’s the mechanism?

There are several mechanisms for this:

  • Infant dyschezia – straining with soft stools in a less than 6-month-old
  • Functional constipation – in infants and preschool children – pebble-like stools less than twice a week
  • Functional faecal retention – holding on, soiling, cramps for at least 12 weeks
  • Functional non-retentive faecal soiling – inappropriate soiling without retention, emotional issues

What about reservoir constipation?

Reservoir constipation is where the stools collect in the bowel and start to get larger and larger.

This is commonly seen in 5-10-year-old boys.

The history is often of passing a large diameter stool every 1-2 weeks. Often because it’s painful to pass these, children can be scared to pass stools and hold them in. This causes the rectum to stretch due to pressure on the rectum. Then the nerves in the wall of the rectum stretch causing a problem with the internal sphincter. A problem with the internal sphincter means that children may be able to hold onto their stools on the journey home (using their external sphincter) but then as soon as they relax at home they will get some soiling.

These children have a numb, toneless rectum which means that they then don’t realise when it’s time to pass stools.

Reservoir constipation can occur because children are too busy to poo, find the toilets too dirty to use (or not private enough), or are scared of pain.

There are other causes of constipation too. For example, there are some psychological causes of encopresis and also some neurological causes. Any clinical examination should be careful to look for neurological signs: check for spina bifida occulta, look for any sinuses or fissures; look for a patulous anus. 

Treating constipation

Emptying the bowels

There are two essential components – stimulants and softeners. In the past, we used enemas and stool softeners. Enemas can be effective, but often you are just unblocking at the bottom end which doesn’t deal with the whole problem.

When discussing the effects of treatment with families, it is useful to be able to recognise the difference between old poo and new poo. Old poo will be dark, hard, and smelly. New poo will be paler, softer, and less smelly. The aim of treatment is to get rid of all the old poo.

Once the bowel is empty and stays empty, it will return to a normal shape and laxity.

Stimulants…

Stimulants can be used to help get things moving – these include laxatives, Senecot, prune juice, Dulcolax tablets (crushed and sprinkled). Senna or bisacodyl directly stimulates the nerve endings in the colon to increase intestinal motility. These are granules which can be eaten plain or mixed with water, milk or food. Cramps and abdominal pain are common. There is some suggestion that it leads to a lazy bowel with long-term use.

Often stimulants will be used temporarily to help empty the bowel and will then be weaned.

With Dulcolax, a typical dose would be:

1 per day for a 5-year-old;
2 per day for a 10-year-old.

It is usually given at 3-4 pm and works within 3-4 hours. So the child usually opens their bowels that evening or the following morning.

Softeners

Osmolax is one of the mainstays of constipation treatment. It simply adds water to the poo which makes it softer and easier to pass. It does not have an effect elsewhere in the body, simply a local effect on the stool. Therefore, it is safe to keep on taking it indefinitely – and some people do.

The best management is to take the same amount every day. Taking it on alternate days, or even just some days, won’t help – the aim is to soften the poo and so that needs to be done regularly. With children, the usual dose is 1-3 scoops per day (although smaller amounts can be used).

Osmolax is given in scoops, and children seem not to object to the taste too much. When weaning Osmolax, wean down the number of scoops per day. Movicol was the precursor to Osmolax. It does the same job, but it contains electrolytes and so children tend not to like the taste as much. Both of these are types of PEG 3350.

Which laxative should I choose?

There are a series of case series and randomized control trials that show treatment with PEG 3350 was effective in causing disimpaction in children with constipation.  The studies show that higher doses are more effective than smaller doses and that PEG 3350 is more effective than stool softeners and enemas (Youssef et al, Tolia et al, Guest et al ). There is currently no evidence of the effectiveness of stimulant laxatives in treating disimpaction.

The NICE ‘Constipation in children and young people guidelines suggest the following management for children over 1 year of age:

Rule out red flags.

Assess for impaction – i.e. overflow soiling and/or faecal mass palpable abdominally. Start maintenance therapy for those not faecally impacted, treat for disimpaction if faecally impacted.



Treat for disimpaction or commence maintenance therapy:

1st line – Macrogol PEG 3350  – escalating dose regime for disimpaction or adjusted according to response in maintenance regime.

2nd line – (2 weeks later) Add a stimulant laxative (e.g. sodium picosulfate,  bisacodyl, senna,)

3rd line – Substitute a stimulant laxative singly or in combination with an osmotic laxative (lactulose) if Macrogol PEG 3350 is not tolerated.

4th line – Enema (stimulant laxative: Microlax or Bisacodyl)

5th line – Manual evacuation under anaesthetic.



Continue maintenance regime for several weeks to months.

Medications are not to be stopped abruptly but to be weaned over a period of months.

What can we give to babies?

In children under 12 months old, just use lactulose or Coloxyl drops. Coloxyl does more than just add water to the stools – it gets absorbed by the body so it is a drug (unlike Osmolax). Both lactulose and Coloxyl are, however, fairly benign. In babies, the cause of constipation can often be due to packing in formula into the bottles (even a 20-30% increase in a formula can cause constipation). In infants <12 months old, there is no good evidence that a high-fibre diet can treat or prevent constipation.

How do we know when we succeed?

Usually, treatment should continue for at least three months to treat reservoir constipation (although can be longer). Once the child is producing normal diameter stools that are not watery then things are returning to a good place. It’s true that everyone is different. In general, aim for bowels to open every day (at least every other day). The stool should be soft and easy to pass.

There is no rush to wean the meds once this is achieved, and often the child also has to unlearn the fear they have about going to the toilet.

What about tough cases of constipation?

A PR examination should only be undertaken by a doctor competent to interpret features of anatomical abnormalities or Hirschsprung’s disease e.g. paediatric surgeons

TFTs and coeliac screens should only be ordered by specialists in patients with intractable constipation

Abdominal x-rays and abdominal ultrasounds are not recommended to aid diagnosis of constipation

Dietary interventions alone are not recommended but should be used in conjunction with a laxative

According to evidence, PEG 3350 (Movicol) should be the oral laxative of choice

Maintenance regimes should be continued for several weeks to months

Routine use of enemas is not recommended

Should I order TFTs and a coeliac screen?

Thyroid function testing and coeliac screening should only be ordered by a specialist service as part of the investigation of intractable constipation when atypical presentations of these diseases are considered. There are no published studies stating the prevalence of coeliac disease and hypothyroidism in children with idiopathic constipation (Reuchlin-Vroklage et al, 2005)

Should I get an abdominal x-ray to confirm my diagnosis?

Abdominal x-rays play little role in confirming, or refuting, the diagnosis of constipation as there is poor diagnostic accuracy and reproducibility (Reuchlin-Vroklage et al, 2005). It is important to remember that the average radiation dose of an abdominal x-ray is 0.7mSv, that’s 7 times higher than a chest x-ray. That is relatively high compared to the background yearly exposure of approximately 3mSv (Mettler et al, 2008).

What about an abdominal ultrasound?

Abdominal ultrasounds have shown that children with idiopathic constipation have a larger rectal diameter than those without constipation. However, they don’t give any extra information than what is obtained through thorough history taking and examination and are therefore not routinely recommended.

Advice and information for parents

Education of the child and family on the physiology of constipation and the mechanism of overflow soiling is important.  Here are some tips, tricks, and general things not to forget.

You can mix the PEG 3350 with other fluids

Whichever Macrogol PEG you use, you can then mix this with cordial, juice, milk or pretty much whatever you like, to disguise the taste.

Dietary advice

Advise the parent to increase fibre and water intake in their child’s diet.

Dietary modifications can make a huge impact. Fibre such as beans, whole grains, cereals and fresh fruit and vegetables are good for improving the symptoms. Foods without fibre (cheese, meat, processed food) should be limited. Plenty of fluids will help keep the stool soft but milk should be limited to less than 500ml per day.

It may be worth referring the child to a dietician for further advice.

Exercise

Daily exercise is recommended to improve bowel motility. A 30-minute walk each day can improve the regularity of bowel motions.

Use a footstool

The best position for defecation is squatting, as there is better alignment of the recto-anal angle. By placing a stool under the child’s feet, and placing the knees above the anus, you are improving the angle, thus relieving any obstruction to stool outflow (Sikirov).

correct positioning to relieve constipation

Positive reinforcement

For most children with constipation, going to the toilet has now become a negative experience.  It is important to encourage parents to give positive feedback to the child when they pass a stool and not to berate them if they were unable to.

Sitting on the toilet should not be an unpleasant experience so encourage the parents to let them read a book, listen to music, or play a computer game.

Reward systems are a good way to aid this positive reinforcement. A good suggestion is using a star chart or bowel diary, where the child gets a sticker every time they sit on the toilet and an extra sticker when they pass a stool. The child can then be involved in deciding a reward for a certain number of stickers gained.

Scheduled toileting

Teach the parents about the gastro-colic reflex – i.e. increased motility of the colon in response to stretch in the stomach after eating. Therefore, the most likely time for the child to pass stool is approximately 15-20 minutes after food (Lowery et al).

If behavioural techniques fail, consider referral to a paediatric occupational therapist for further advice.

Where can I find a good information sheet?

Good information sheets for parents

Good websites to refer parents to

References

Bracewell M, Bunce N.  Movicol Paediatric Plain: A Treatment for Constipation in Children.  Sussex Community NHS.  2009 July. https://gp.westernsussexhospitals.nhs.uk/wp-content/uploads/gpsiteweb/Leaflet11movicol-AssetID=354390&type=full&servicetype=Attachment.pdf

Dosage guides are provided in the guideline – https://guidance.nice.org.uk/CG99.

Candy DC, Edwards D, Geraint M. Treatment of faecal impaction with polyethylene glycol plus electrolytes (PGE + E) followed by a double-blind comparison of PEG + E versus lactulose as maintenance therapy. Journal of Pediatric Gastroenterology and Nutrition. 2006;43(1):65-70.

Guest JF, et al. Clinical and economic impact of using macrogol 3350 plus electrolytes in an outpatient setting compared to enemas and suppositories and manual evacuation to treat paediatric faecal impaction based on actual clinical practice in England and Wales. Current Medical Research and Opinion. 2007;23(9):2213-25.

Lowery S, et al. Habit Training as Treatment of Encopresis secondary to Chronic Constipation.  Journal of Pediatric Gastroenterology & Nutrition. 1985 June;4(3):397-401.

Mettler FA, et al.  Effective Doses in radiology and Diagnostic Nuclear Medicine: A Catalog. Radiology. 2008 Jul ;248(1):254-63.

National Institute for Health and Clinical Excellence (2010).  Constipation in children and young people: diagnosis and management of idiopathic childhood constipation in primary and secondary care. CG99. London: National Institute for Health and Clinical Excellence. Available from: https://www.nice.org.uk/guidance/CG99

Pashankar DS and Bishop WP. Efficacy and optimal dose of daily polyethylene glycol 3350 for treatment of constipation and encopresis in children. Journal of Pediatrics. 2001;139(3):428-32.

Reuchlin-Vroklage LM, et al. Diagnostic value of abdominal radiography in constipated children: a systematic review. Archives of Pediatrics and Adolescent Medicine. 2005;159(7):671-8.

Sikirov BA. Primary Constipation: An underlying mechanism.  Medical Hypotheses. 1989 February;28(2):71-73.

Tolia V, et al. A prospective randomized study with mineral oil and oral lavage solution for treatment of faecal impaction in children.  Alimentary Pharmacology and Therapeutics. 1993;7(5):523-9.

Youssef NN, et al. Dose response of PEG 3350 for the treatment of childhood fecal impaction. Journal of Pediatrics. 2002;141(3):410-4.

Authors

  • Dr Angela Clarke MBBS, DCH is a paediatric trainee based in Brisbane, Queensland. She has a special interest in General Paediatrics, Medical Education and Paediatric Emergency Medicine. Outside of work she enjoys gardening, cooking and exploring South East Queensland by land and sea.

  • Tessa Davis is a Consultant in Paediatric Emergency Medicine at the Royal London Hospital and a Senior Lecturer at Queen Mary University of London.

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1 thought on “Constipation”

  1. Thank you so much for this information. This additional to what our specialist provided, and has helped me to understand better how PEG 3350 works, why it does not cause dependency, and that it can help in particular with impaction. An extremely helpful, and calming article. Thank you.

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