Paediatric diarrhoea

Contributed by Professor Terence Stephenson, professor of child health and consultant paediatrician, Nottingham University Hospitals NHS Trust.

1. Epidemiology and aetiology 

Diarrhoea in children is an extremely common problem. Of all children presenting to our A&E department without trauma, 16 per cent are there because of vomiting or diarrhoea. This is the tip of the iceberg because most cases are managed by GPs.

Diarrhoea can be acute or chronic.

Acute diarrhoea
The most common cause of acute diarrhoea is gastroenteritis, which may be accompanied by fever. In the UK, most gastroenteritis is viral, mostly rotavirus and mostly in infants and toddlers.

Bloody diarrhoea suggests a bacterial infection (most commonly Campylobacter or E coli); a surgical cause (for example intussusception) in a young child; or the onset of inflammatory bowel disease in an older child. All such children should be referred to hospital urgently.

Certain strains of E coli can cause haemolytic uraemic syndrome, which can lead to renal failure and coagulopathy. 'Redcurrant jelly' stools, abdominal distension and bilious vomiting suggest intussusception, usually in children aged three months to three years.

Chronic diarrhoea Distinguish between faecal overflow (due to constipation) and true diarrhoea by abdominal and rectal examination.

If growth is normal, toddler diarrhoea or post-gastroenteritis food intolerance are most likely. If growth is faltering, consider malabsorption. Inflammatory bowel disease is rare.

2. Making a diagnosis
Gastroenteritis can cause vomiting alone, vomiting and diarrhoea or just diarrhoea. Ask about diarrhoea or vomiting in other family members, in the nursery or school, and recent travel abroad.

Food poisoning is often from undercooked or inadequately reheated food: Salmonella from poultry, E coli from beef and Bacillus cereus from rice.

The main risk from acute diarrhoea is dehydration.

Assessing dehydration is difficult but signs include dry mucous membranes, sunken eyes, diminished skin turgor, tachycardia, altered neurological status (drowsiness, irritability) and deep (acidotic) breathing. Heart rate is the most objective. The upper limit of normal for heart rate in an afebrile child under five years is approximately 180 minus the child's age in months. Any child with diarrhoea who has a heart rate above this should be presumed to be more than 3 per cent dehydrated. Allow an increase with fever of approximately 10 beats per minute for each degree centigrade above 37 deg C.

Children who are severely dehydrated should be admitted to hospital.

Children with mild-to-moderate dehydration or those at high risk of dehydration (infants <6 months; high frequency of watery stools (more than eight per 24 hours) or vomits (more than four per 24 hours)) should probably be observed in a paediatric facility for a period of at least six hours to ensure successful rehydration (three to four hours) and maintenance of hydration (two to three hours).

The following clinical features should alert the clinician to look for causes other than acute viral gastroenteritis for a child's diarrhoea: abdominal pain with tenderness, with or without guarding, pallor, jaundice, oligo/anuria, bloody diarrhoea, systemically unwell - out of proportion to the level of dehydration and shock.

Investigations
In straightforward acute diarrhoea presumed to be due to viral gastroenteritis, there is little role for stool culture as the illness will usually have resolved by the time the report is available.

In prolonged diarrhoea or after travelling abroad, stool should be sent for microscopy and culture. In bloody diarrhoea or an illness thought to be food poisoning, stool cultures should always be sent as there may be public health issues relating to food outlets.

Definitive diagnosis of the cause of chronic diarrhoea may require a sweat test (for cystic fibrosis); blood tests of immune function; upper or lower GI endoscopy; duodenal biopsy (for coeliac disease); aspiration and culture of duodenal juices (for giardiasis); small bowel biopsy (for Crohn's disease); large bowel biopsy (for colitis); or radiological contrast studies.

3. Treatment

Oral fluid rehydration, even in the child who is vomiting, is the mainstay of management of gastroenteritis in the community and hospital.

If the child is less than 3 per cent dehydrated and being managed in the community, it is simplest to ignore the mild deficit and recommend maintenance oral fluid as a glucose/electrolyte solution for the next 24 hours.

However, if the child sleeps for eight hours in the next 24, then just over 100ml/hour will be the target intake while awake. This is best given 'little and often'. In this example, this would be 25ml every quarter of an hour - a cup is 180ml on average.

In a child over one year-old, food intake is unimportant in the short-term until vomiting settles and appetite returns.

A breastfed child should still be offered the breast after glucose/electrolyte solution in volumes as recommended above.

A formula-fed infant can recommence undiluted feeds after glucose/electrolyte solution if there has been no vomiting for four hours.

Kaolin or antispasmodics should be avoided and antibiotics are only indicated for specific infections, for example, erythromycin or ciprofloxacin for prolonged Campylobacter infection; ciprofloxacin or trimethoprim for Salmonella bacteraemia; and metronidazole for Giardia.

Complications of gastroenteritis

Diarrhoea persisting beyond two weeks might be a transient intolerance.

Transient intolerances tend only to last for a few weeks and normal diet should be resumed after this period.

For transient lactose intolerance, which can occur after gastroenteritis, try a lactose-free milk.

There may be a generalised disaccharidase deficiency, in which case Pregestimil may be useful.

In transient protein intolerance try a hydrolysed casein milk or also a soya-based milk.

However, soya-protein intolerance may co-exist with cow's milk intolerance.

New developments
In 1999, the Rotashield vaccine against rotavirus was withdrawn after an association with intussusception was noted.

The FDA in the US recently licensed a new rotavirus vaccine following trials in Finland and the US. The trial vaccine was given to infants under the age of three months, an age when intussusception is rare.

A rotavirus vaccine was also recently licensed in Europe.

ORAL HYDRATION FLUID REQUIREMENTS
Requirements by weight

- 100ml/kg/day for the first 10kg body weight
- 50ml/kg/day for the next 10kg body weight
- 20ml/kg/day for the each kilogram above 20kg
Example: 30kg child
- 100ml/kg for first 10kg = 1,000ml
- 50ml/kg for next 10kg = 500ml
- 20ml/kg for remaining 10kg = 200ml
Total: 1,700ml per 24 hours (70ml/hour)

Further reading

  • Armon K, Stephenson T, MacFaul R, Eccleston P, Werneke U. A guideline for acute diarrhoea management. Arch Dis Child 2001; 85: 132-42.
  • O'Callaghan C, Stephenson T. Pocket Paediatrics. Second edition. Churchill Livingstone, Edinburgh, 2004.
  • Davies P, Maconochie I. It's getting hot in here: a quantification of the relation between body temperature and heart rate. Arch Dis Child 2007; 92(Suppl 1): A10.

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