Suspect gastroenteritis if there is a sudden change in stool consistency to loose or watery stools, and/or a sudden onset of vomiting. The clinician should be aware that in children with gastroenteritis:
- diarrhoea usually lasts for 5-7 days, and in most it stops within 2 weeks
 - vomiting usually lasts for 1-2 days, and in most it stops within 3 days (1)
 
A complete history and physical examination should be carried out to determine whether the child is dehydrated and if possible the aetiology of acute gastroenteritis (2,3)
- duration of illness
 - the number of episodes per day
- vomiting
- whether vomiting is interfering with the child's ability to keep down fluids and solid food
 - type of emesis (e.g., whether bile is present)
 
 - diarrhoea
- whether blood or mucus is present
 
 
 - urine output
 - the presence of blood in the stool
 - accompanying symptoms such as fever, abdominal pain, and urinary complaints
 - child's mental status
 - any accompanying medical conditions
 - whether oral rehydration therapy has been attempted with any success
 - 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 (1,2,3)
 
Physical examination can be useful in identifying signs of dehydration e.g. - level of alertness, presence of sunken eyes, dry mucous membranes, and skin turgor
Recognise that the following are at increased risk of dehydration:
- children younger than 1 year, particularly those younger than 6 months
 - infants who were of low birth weight
 - children who have passed more than five diarrhoeal stools in the previous 24 hours
 - children who have vomited more than twice in the previous 24 hours
 - children who have not been offered or have not been able to tolerate supplementary fluids before presentation
 - infants who have stopped breastfeeding during the illness
 - children with signs of malnutrition (1).
 
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