Gastroenteritis Guidelines

Gastroenteritis, also known as infectious diarrhea, is inflammation of the gastrointestinal tract that involves the stomach and small intestine. Signs and symptoms include some combination of diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration may also occur. This typically lasts less than two weeks. It is unrelated to influenza though it has been 

called the "stomach flu". Gastroenteritis can be due to infections by viruses, bacteria, parasites, and fungus. The most common cause is viruses. In children rotavirus is the most common cause of severe disease. In adults, norovirus and Campylobacter are common. Transmission may occur due to eating improperly prepared foods, drinking contaminated water, or through close contact with an individual who is infected. Testing to confirm the diagnosis is typically not needed.

Prevention includes hand washing with soap, drinking clean water, proper disposal of human waste, and breastfeeding babies instead of using formula. The rotavirus vaccine is recommended in children. Treatment involves getting enough fluids. For mild or moderate cases, this can typically be achieved by drinking oral rehydration solution (a combination of water, salts, and sugar). In those who are breast fed, continued breastfeeding is recommended. For more severe cases, intravenous fluids may be needed. Fluids may also be given by a nasogastric tube. Zinc supplementation is recommended in children. Antibiotics are generally not needed.


  • Infectious gastroenteritis causes diarrhea with or without vomiting
  • Cramping abdominal pain
  • Many cases can be managed effectively with oral rehydration
  • Enteral rehydration is preferable to intravenous hydration
  • Shocked patients require urgent resuscitation with 20 mls/kg boluses of  IV Normal Saline


Is the diagnosis of gastroenteritis correct
The following features may occur in gastroenteritis, but should prompt careful consideration of differential diagnoses & review by a senior doctor

  • Severe abdominal pain or abdominal signs
  • Persistent diarrhea (10 days)
  • Blood in stool
  • Looks very unwell
  • Bilious (green) vomit
  • Vomiting without diarrhea

Consider the diagnosis carefully if there is

  • Abdominal pain
  • Isolated Vomiting


In most patients with gastroenteritis no investigations are required. Faecal samples may be collected for microbiological culture if the patient has significant associated abdominal pain or blood in the motions, as a bacterial cause of gastroenteritis is more likely. However these results usually don't alter treatment. Blood tests (electrolytes, glucose) are not necessary in simple gastroenteritis but are required for

  • Severe dehydration
  • Comorbidity of renal disease or on diuretics
  • Altered conscious state
  • Ileostomy

Acute Management


  • Ondansetron Drug Dose
  • Should only be administered once in this setting
  • Oral Rehydration
  • Lemonade, homemade ORS and sports drinks are not appropriate fluids for rehydration
  • Suggest oral rehydration solutions (ORS) eg. Pedialyte

Trial of oral fluids in the emergency department

  • Note: Most patients with mild/no dehydration can be discharged without a trial of  fluids,  after appropriate advice and follow-up arranged
  • In patients requiring rehydration: give frequent small amounts of ORS, aiming for 10-20 ml/kg over 1 hour
  • Significant ongoing GI losses (frequent vomiting or profuse diarrhoea) minimise the chance of success at home. Consider early NGT rehydration in these children

Intravenous Rehydration

  • Indicated for severe dehydration. (eg. ongoing profuse losses or abdominal pain)
  • Also suitable for patients who already have an IV insitu

IV Fluids Guidelines

  • Initial boluses: 20ml/kg Normal saline boluses, repeated until shock is corrected. If 40 ml/kg boluses required, involve senior staff and ICU
  • Measure blood glucose and treat hypoglycaemia with 5ml/kg of 10%  dextrose
  • Measure Na, K and glucose at the outset & at least 24 hourly from then on (more frequent testing is indicated for patients with co-morbidities or if more unwell). Venous blood gases provide rapid results. It is not necessary to send an electrolyte tube to the lab unless measurement of urea or creatinine is clinically indicated. Consider septic work-up or surgical consult in severely unwell patients with gastroenteritis
  • Ongoing fluids: 5% Dextrose + 0.9% Normal saline (Rates see table). Use a fluid containing KCl (20mmol/L) if serum K < 3mmol/l or give oral supplements