Acute gastritis is inflammation of the stomach and presents with nausea and vomiting. Enteritis is inflammation of the intestines and presents with diarrhoea. Gastroenteritis is inflammation all the way from the stomach to the intestines and presents with nausea, vomiting and diarrhoea.

Gastroenteritis is a very common condition in children. The most common cause of gastroenteritis is viral. It is very easily spread and patients presenting with gastroenteritis often have an affected family member or contact.

It is essential to isolate the patient in any healthcare environment, such as a paediatric assessment unit or hospital ward, as they can easily spread it to other patients.

Dehydration is the main concern. The key to management is establishing whether they are able to keep themselves hydrated or whether they need admission for IV fluids. Antibiotics are generally not recommended or required. Most children make a full recovery with simple supportive management, but beware gastroenteritis can potentially be fatal, especially in very young or vulnerable children with other health conditions.


Differential Diagnosis of Diarrhoea

Loose stools are a common complaint and not all cases are caused by gastroenteritis. Stools from normal babies can vary from loose stools several times a day to one stool per week. Steatorrhoea means greasy stools with excessive fat content. This suggests a problem with digesting fats, such as pancreatic insufficiency (think about cystic fibrosis).

Key conditions to think about in patients with loose stools are:

  • Infection (gastroenteritis)
  • Inflammatory bowel disease
  • Lactose intolerance
  • Coeliac disease
  • Cystic fibrosis
  • Toddler’s diarrhoea
  • Irritable bowel syndrome
  • Medications (e.g. antibiotics)


Viral Gastroenteritis

Viral gastroenteritis is common. It is highly contagious. Common causes are:

  • Rotavirus
  • Norovirus

Adenovirus is a less common cause and presents with a more subacute diarrhoea.


E. coli

Escherichia coli (E. coli) is a normal intestinal bacteria. Only certain strains cause gastroenteritis. It is spread through contact with infected faeces, unwashed salads or contaminated water.

E. coli 0157 produces the Shiga toxin. This causes abdominal cramps, bloody diarrhoea and vomiting. The Shiga toxin destroys blood cells and leads to haemolytic uraemic syndrome (HUS).

The use of antibiotics increases the risk of haemolytic uraemic syndrome, therefore antibiotics should be avoided if E. coli gastroenteritis is considered.


Campylobacter Jejuni

Campylobacter is a common cause of travellers diarrhoea. It is the most common bacterial cause of gastroenteritis worldwide. Campylobacter means “curved bacteria”. It is a gram negative bacteria that has a curved or spiral shape. It is spread by:

  • Raw or improperly cooked poultry
  • Untreated water
  • Unpasteurised milk

Incubation is usually 2 to 5 days. Symptoms resolve after 3 to 6 days. Symptoms are:

  • Abdominal cramps
  • Diarrhoea often with blood
  • Vomiting
  • Fever

Antibiotics can be considered after isolating the organism where patients have severe symptoms or other risk factors such as HIV or heart failure. Popular antibiotic choices are azithromycin or ciprofloxacin.



Shigella is spread by faeces contaminating drinking water, swimming pools and food. The incubation period is 1 to 2 days and symptoms usually resolve within 1 week without treatment. It causes bloody diarrhoea, abdominal cramps and fever. Shigella can produce the Shiga toxin and cause haemolytic uraemic syndrome. Treatment of severe cases is with azithromycin or ciprofloxacin.



Salmonella is spread by eating raw eggs or poultry, or food contaminated with the infected faeces of small animals. Incubation is 12 hours to 3 days and symptoms usually resolve within 1 week. Symptoms are watery diarrhoea that can be associated with mucus or blood, abdominal pain and vomiting. Antibiotics are only necessary in severe cases and should be guided by stool culture and sensitivities.


Bacillus Cereus

Bacillus cereus is a gram positive rod spread through inadequately cooked food. It grows well on food not immediately refrigerated after cooking. The typical food is fried rice left out at room temperature.

Whilst growing on food it produces a toxin called cereulide. This toxin causes abdominal cramping and vomiting within 5 hours of ingestion. When it arrives in the intestines it produces different toxins that cause a watery diarrhoea. This occurs more than 8 hours after ingestion. All of the symptoms usually resolves within 24 hours.

The typical course is vomiting within 5 hours, then diarrhoea after 8 hours, then resolution within 24 hours.

TOM TIP: The typical exam patient with bacillus cereus develops symptoms soon after eating leftover fried rice that has been left at room temperature. It has a short incubation period after eating the rice before symptoms occur, and they recover within 24 hours. Examiners like this question because the course of bacillus cereus is easy to distinguish from the other causes of gastroenteritis, so if you remember one cause of gastroenteritis this is probably the most likely to come up in exams.


Yersinia Enterocolitica

Yersinia is a gram negative bacillus. Pigs are key carriers of Yersinia, and eating raw or undercooked pork can cause infection. It is also spread through contamination with the urine or faeces of other mammal such as rats and rabbits.

Yersinia most frequently affects children, causing watery or bloody diarrhoea, abdominal pain, fever and lymphadenopathy. Incubation is 4 to 7 days and the illness can last longer than other causes of enteritis with symptoms lasting 3 weeks or more. Older children or adults can present with right sided abdominal pain due mesenteric lymphadenitis (inflammation in the intestinal lymph nodes) and fever. This can give the impression of appendicitis.

Antibiotics are only necessary in severe cases and should be guided by stool culture and sensitivities.


Staphylococcus Aureus Toxin 

Staphylococcus aureus can produce enterotoxins when growing on food such as eggs, dairy and meat. When eaten these toxins cause small intestine inflammation. This causes symptoms of diarrhoea, perfuse vomiting, abdominal cramps and fever. These symptoms start within hours of ingestion and settle within 12 to 24 hours. It is not actually the bacteria causing the enteritis but the staphylococcus enterotoxin.



Giardia lamblia is a type of microscopic parasite. It lives in the small intestines of mammals. These mammals may be pets, farmyard animals or humans. It releases cysts in the stools of infected mammals. The cysts contaminate food or water and are eaten, infecting a new host. This is called faecal-oral transmission.

Infection may not cause any symptoms, or it may cause chronic diarrhoea. Diagnosis is made by stool microscopy. Treatment is with metronidazole.


Principles of Gastroenteritis Management

Good hygiene helps prevent gastroenteritis. When patients develop symptoms they should immediately be isolated to prevent spread. Barrier nursing and rigorous infection control is important for patients in hospital to prevent spread to other patients. Children need to stay off school until 48 hours after the symptoms have completely resolved.

A sample of the faeces can be tested with microscopy, culture and sensitivities to establish the causative organism and antibiotic sensitivities.

The key to managing gastroenteritis is to ensure they remain hydrated whilst waiting for the diarrhoea and vomiting to settle. Attempt a fluid challenge. Each hospital will have a policy for this. It involves recording a small volume of fluid given orally every 5-10 minutes to ensure they can tolerate it. If they are able to tolerate oral fluid and are adequately hydrated they can usually be managed at home. Rehydration solutions (e.g. dioralyte) can be used if tolerated. Dehydrated children or those that fail the fluid challenge may require IV fluids.

Once oral intake is tolerated a light diet can be slowly reintroduced. Dry foods such as toast may be better tolerated.

Antidiarrhoeal medication such as loperamide and antiemetic medication such as metoclopramide are generally not recommended. Antidiarrhoeal medications are particularly avoided in e. coli 0157 and shigella infections, and where there is bloody diarrhoea or high fever.

Antibiotics should only be given in patients that are at risk of complications once the causative organism is confirmed.


Post Gastroenteritis Complications

The are possible post-gastroenteritis complications:

  • Lactose intolerance
  • Irritable bowel syndrome
  • Reactive arthritis
  • Guillain–Barré syndrome


Last updated August 2019