Acute gastritis is stomach inflammation and presents with epigastric discomfort, nausea and vomiting. Enteritis is inflammation of the intestines, and presents with abdominal pain and diarrhoea. Gastroenteritis is inflammation all the way from the stomach to the intestines and presents with pain, nausea, vomiting and diarrhoea.
The most common causes of gastroenteritis are viruses. Viral gastroenteritis is very easily spread, and patients often have an affected family member or contact. It is essential to isolate the patient in a healthcare environment, such as a hospital ward or assessment unit, as it can spread to other patients.
Most people recover well. However, gastroenteritis can rarely be fatal, especially in very young or old patients or those with other health conditions.
Viral Gastroenteritis
Viral gastroenteritis is common. It is highly contagious. Specific viruses include:
- Rotavirus
- Norovirus
- Adenovirus (tends to cause respiratory symptoms)
Escherichia 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 and contaminated water.
E. coli 0157 produces the Shiga toxin. The Shiga toxin causes abdominal cramps, bloody diarrhoea and vomiting. It also destroys blood cells, leading 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 a possibility.
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 is curved or spiral-shaped. 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. Clarithromycin is often first-line. Azithromycin and ciprofloxacin are alternative options.
Shigella
Shigella is spread via faeces, either person-to-person or through contaminated drinking water or food. The incubation period is 1-2 days, and symptoms usually resolve within one week. It causes bloody diarrhoea, abdominal cramps and fever. Shigella can produce the Shiga toxin, which can cause haemolytic uraemic syndrome. Treatment of severe cases is with azithromycin or ciprofloxacin.
Salmonella
Salmonella is spread by eating raw eggs or poultry or food contaminated with the infected faeces of small animals. The incubation period is 12 hours to 3 days, and symptoms usually resolve within one week. Symptoms are watery diarrhoea, which may be associated with mucus or blood, abdominal pain and vomiting. Antibiotics are only necessary in severe cases and are guided by stool culture and sensitivities (e.g., ciprofloxacin).
Bacillus Cereus
Bacillus cereus is a gram-positive rod spread through contaminated cooked food. It grows on food not immediately refrigerated after cooking (e.g., fried rice or cooked pasta left at room temperature).
Whilst growing on the food, it produces a toxin called cereulide that causes abdominal cramping and vomiting within 5 hours of ingestion. Reheating the food can kill the bacteria but does not destroy the cereulide toxin. When Bacillus cereus arrives in the intestines, it produces different toxins that cause watery diarrhoea. Diarrhoea occurs more than 8 hours after ingestion. All of the symptoms usually resolve within 24 hours.
The typical course is vomiting within 5 hours, diarrhoea after 8 hours and resolution within 24 hours.
TOM TIP: The typical exam patient with Bacillus cereus develops symptoms soon after eating fried rice that has been left at room temperature. They develop symptoms shortly afterwards, then recover within 24 hours. Examiners like this question because the course is easily distinguished from other causes of gastroenteritis.
You may also come across Bacillus cereus with infective endocarditis in intravenous drug users (IVDU), where heroin is contaminated. However, Staph aureus is the most common cause of infective endocarditis in IVDU.
Yersinia Enterocolitica
Yersinia enterocolitica is a gram-negative bacillus. Pigs are key carriers, and eating raw or undercooked pork can cause infection. It is also spread through contact with infected humans, animals or faeces.
Yersinia typically affects children, causing watery or bloody diarrhoea, abdominal pain and fever. Incubation is 4-7 days. It can last longer than other causes of enteritis, with symptoms lasting 3 weeks or more. Older children and adults can present with right-sided abdominal pain due to mesenteric lymphadenitis (inflammation in the intestinal lymph nodes) and fever, which can give the impression of appendicitis.
Antibiotics are only necessary in severe cases and are guided by stool culture and sensitivities.
Yersinia pestis (a different specie of Yersinia) is spread through rat flea bites and causes plague.
Staphylococcal Enterotoxins
Staphylococcus aureus can produce enterotoxins when growing on foods such as eggs, dairy and meat. When eaten, these toxins cause inflammation in the intestines, with symptoms of diarrhoea, vomiting, abdominal cramps and fever. These symptoms start within hours of ingestion and settle within 12 to 24 hours. It is the enterotoxin causing symptoms rather than the bacteria.
Giardiasis
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 faeces. The cysts may contaminate food or water. When eaten, they infect 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 testing (NAAT or EIA testing). Treatment is with tinidazole or metronidazole.
General Principles of Management
Food poisoning is a notifiable disease. The UK Health Security Agency (UKHSA) should be notified of suspected cases. When notifiable organisms (e.g., Giardia) are identified on testing, the lab must notify UKHSA.
Good hygiene helps prevent gastroenteritis. When patients develop symptoms, they should immediately be isolated in order to avoid spread. Barrier nursing and rigorous infection control are important for inpatients.
A faeces sample can be tested with microscopy, culture and sensitivities to establish the causative organism and antibiotic sensitivities.
Dehydration is the primary concern. The key to management is establishing whether patients can keep themselves hydrated or need admission for IV fluids. Antibiotics are generally not recommended or required. Most patients make a full recovery with simple, supportive management.
Oral rehydration salt solution (e.g., Dioralyte sachets mixed with water) can help replace losses in patients at increased risk of dehydration (e.g., frail patients). These contain glucose, potassium and sodium.
Antidiarrhoeal drugs (e.g., loperamide) and antiemetics (e.g., metoclopramide) are generally avoided, as they can worsen the condition. The NICE Clinical Knowledge Summaries (updated June 2023) suggest antidiarrhoeal drugs may be helpful in mild-moderate diarrhoea but should be avoided with E. coli 0157, shigella or bloody diarrhoea.
Antibiotics are only used in patients at risk of complications once the causative organism is confirmed.
Once the oral intake is better tolerated, a light diet with small quantities of bland foods can be introduced. Patients should stay off work or school for 48 hours after symptoms resolve entirely.
Post-Gastroenteritis Complications
- Lactose intolerance
- Irritable bowel syndrome
- Reactive arthritis
- Guillain–Barré syndrome
- Haemolytic uraemic syndrome
Last updated July 2023
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