Page 52 - 15Diarrhoeaandvomiting

Diagnosis

The GDG also considered that the main conditions in the differential diagnosis of gastroenteritis
include non-enteric infections, non-infective gastrointestinal disorders, abdominal surgical
disorders and antibiotic-associated diarrhoea. It was agreed that, if vomiting persisted for more
than 24 hours without diarrhoea, diagnoses other than gastroenteritis (for example, urinary tract
infection) should be considered.

Recommendations on diagnosis
If you suspect gastroenteritis, ask about:
• recent contact with someone with acute diarrhoea and/or vomiting and
• exposure to a known source of enteric infection (possibly contaminated water or food) and
• recent travel abroad.

Consider any of the following as possible indicators of diagnoses other than gastroenteritis:
• fever:
– temperature of 38 °C or higher in children younger than 3 months
– temperature of 39 °C or higher in children aged 3 months or older
• shortness of breath or tachypnoea
• altered conscious state
• neck stiffness
• bulging fontanelle in infants
• non-blanching rash
• blood and/or mucus in stool
• bilious (green) vomit
• severe or localised abdominal pain
• abdominal distension or rebound tenderness.

3.2 Laboratory investigations in diagnosis

Introduction
Most children with gastroenteritis do not require any laboratory investigations. Many infants
and children experience brief episodes of diarrhoea and are managed by their parents without
seeking professional advice. Even if advice is sought, healthcare professionals often consider
that a clinical assessment is all that is required, and laboratory investigations are not undertaken.
However, there may be particular circumstances when investigations may be helpful in diagnosis.

3.2.1 Stool microbiological investigation
In clinical practice, most children with gastroenteritis do not undergo any stool investigations
and no attempt is made to identify the presumptive enteric pathogen. In some cases, however,
microbiological investigation may be appropriate. There might be circumstances in which
identification would be important. Some pathogens are of special significance. For example,
amoebic dysentery would require antimicrobial therapy. Escherichia coli O157:H7 is associated
with a risk of haemolytic uraemic syndrome (HUS) – a serious and potentially deadly disorder.
Bloody diarrhoea may be caused by serious non-infective conditions such as inflammatory
bowel disease (ulcerative colitis or Crohn’s disease) and isolation of a bacterial pathogen might
therefore be diagnostically helpful.
It was therefore important to determine the frequency with which enteric pathogens were identified
by stool microbiological investigation. An additional group for consideration was the child with
diarrhoea recently returned from overseas travel in whom the likely pathogens might differ.

Clinical question
In what proportion of children with a clinical diagnosis of gastroenteritis is a causative enteric
pathogen identified? What is the incidence of specific pathogens?

It was important to first determine how frequently enteric pathogens can be found in children with
gastroenteritis in the UK. The evidence to inform this question was taken from eight published
studies from England and Wales and the website of the Health Protection Agency (HPA).

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