Constipation week – Day 4: Evidence on Tough Topics

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Bottom line: (pun definitely intended!)

  • 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 screen should only be ordered by specialists in patients with intractable constipation
  • Abdominal xrays 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

See our other Constipation Week posts

Do I order TFTs and 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?

Evidence shows that 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.

Which laxative do I choose?

There are a series of case series and randomized control trials that show treatment with PEG 3350 was effective in causing disimpaction of 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:

  1. Rule out ‘Red flags’.
  2. 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.
  3. 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 not tolerated.
    • 4th line – Enema (stimulant laxative: Microlax or Bisacodyl)
    • 5th line – Manual evacuation under anaesthetic.
  4. Continue maintenance regime for several weeks to months.
  5. Medications not to be stopped abruptly but to be weaned over a period of months.

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

 

References

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.

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

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

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.

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.

Candy DC, Edwards D, Geraint M. Treatment of faecal impaction with polyethelene 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.

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.

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About 

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.