The Health Protection Agency defines acute diarrhoea as 3 or more episodes of partially formed or watery stool in a day, lasting for less than 14 days. Infective gastroenteritis is the most common cause of diarrhoea, with or without vomiting, in young children. Viral infections account for most cases in the developed world, although bacteria or protozoal pathogens may also be responsible. A European study found that approximately 10% of children under 5 years present to healthcare services with gastroenteritis each year. Rotavirus infection accounted for 28–52% of cases of gastroenteritis identified (Van Damme et al. 2007). In the UK, from September 2013, oral vaccination against rotavirus will be offered to infants as part of their routine vaccination programme.

Parents often manage an episode of acute diarrhoea affecting their child at home, and in some cases without seeking professional advice. However, many parents and carers do seek advice from healthcare professionals. In a UK study (Armon et al. 2001), diarrhoeal illness accounted for 16% of medical presentations to a major paediatric accident and emergency department.

The NICE clinical guideline on diarrhoea and vomiting in children under 5 advises that the usual duration of diarrhoea is 5–7 days and in most children it stops within 2 weeks. Vomiting usually lasts 1 or 2 days and generally stops within 3 days. The guideline recommends that advice should be sought from a healthcare professional if a child's symptoms do not resolve within these timeframes or if signs or symptoms of dehydration develop.

In children who are not clinically dehydrated, the guideline advises that usual feeds, including breast or other milk feeds, should be continued, and that children should be encouraged to drink plenty of fluids (not including fruit juices and carbonated drinks). The guideline also recommends that children who are at increased risk of dehydration should be offered oral rehydration salt (ORS) solution (see the NICE clinical guideline for more information on assessing dehydration and shock).

The NICE clinical guideline on diarrhoea and vomiting in children under 5 advises that 50 ml/kg low-osmolarity ORS solution (240–250 mOsm/l) should be given over 4 hours, frequently and in small amounts, to children with clinical dehydration. The British national formulary (BNF) for children (December 2012) lists the following products with this composition: Dioralyte, Dioralyte Relief and Electrolade. Supplementation with usual fluids (including milk feeds or water, but not fruit juices or carbonated drinks) should be considered in children who refuse to take sufficient quantities of ORS solution and do not have red flag symptoms or signs (see table 1 of the guideline for more information). The guideline also recommends that nasogastric administration of ORS solution be considered in children who are unable to drink the solution or who vomit persistently.

The NICE clinical guideline on diarrhoea and vomiting in children under 5 also advises that intravenous fluid therapy should be used for clinical dehydration if shock is suspected or confirmed; if a child with red flag symptoms or signs shows clinical evidence of deterioration despite oral rehydration therapy; or if a child persistently vomits the ORS solution, given orally or through a nasogastric tube.

The guideline also advises that antidiarrhoeal medications should not be used. These include adsorbent agents (such as kaolin, smectite and activated charcoal), bismuth salicylate, antisecretory agents (including racecadotril, which was not licensed in the UK when the guideline was published) and antimotility agents. Although some antimotility agents such as loperamide syrup and co-phenotrope tablets are licensed in children aged 4 years and over, the BNF for children advises that they are not recommended for use in children aged under 12 years. The BNF for children also advises that antispasmodics and antiemetics should be avoided in young children with gastroenteritis because they are rarely effective and have troublesome adverse effects.