Mild dehydration which is being treated with oral fluids requires no further investigation.
Diagnosis and investigations:
- a stool sample is not a mandatory investigation in case of diarrhoea and vomiting in children  
- stool microbiological investigations should be performed if:
 - septicaemia is suspected or
 - there is blood and/or mucus in the stool or
 - the child is immunocompromised
 - in other circumstances when stool microbiological investigations should be considered include: 
- the child has recently been abroad or
 - the diarrhoea has not improved by day 7 or
 - there is uncertainty about the diagnosis of gastroenteritis
 
 
 - blood cultures
- if giving antibiotic therapy then perform a blood culture
 
 - blood biochemical testing is not routinely indicated
- measurement of plasma sodium, potassium, urea, creatinine and glucose concentrations is indicated if:
- intravenous fluid therapy is required or
 - there are symptoms and/or signs that suggest hypernatraemia
 
 
 - venous blood acid-base status and chloride concentration is indicated if shock is suspected or confirmed
 
If the diarrhoea is bloody then a full blood count, blood cultures and urea and electrolytes should be performed. If the haemoglobin is low then haemolytic uraemic syndrome should be considered and a film should be asked for to see if there are fragmented red blood cells.
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