Gastroenteritis in Adults and Older Children

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: Food Poisoning in Children written for patients

Gastroenteritis is a nonspecific term used to describe a condition in which there is a combination of nausea, vomiting, diarrhoea and abdominal pain. The term is usually taken to mean those of infectious origin. See also separate article Gastroenteritis in Children.

  • Gastroenteritis is caused by a variety of viral (eg, norovirus, rotavirus and adenovirus), bacterial (eg, Campylobacter spp., Escherichia coli O157, Salmonella spp., Shigella spp., or toxins from Staphylococcus aureus, Bacillus cereus or Clostridium perfringens) and parasitic pathogens (eg, Cryptosporidium spp., Entamoeba histolytica (amoebiasis) or Giardia lamblia).
  • About 20% of the UK population develop infectious intestinal disease each year.[1] 
  • Viral infections cause 30-40% of gastroenteritis cases in industrialised countries. The figure is higher for children. Norovirus is the most common cause of viral infectious gastroenteritis in adults in England and Wales. Adenovirus and rotavirus are much less common in teenagers than in younger children.
  • The 2014 Ebola virus outbreak is one of the largest Ebola outbreaks in history and the first in West Africa.
  • The causative agent for most cases of gastroenteritis is never isolated and the responsible agent never diagnosed. Management is not usually dependent upon cause.

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Risk factors

  • Poor personal hygiene and lack of sanitation increase the incidence.
  • A compromised immune system leaves the patient vulnerable to gastroenteritis - eg, AIDS.
  • Achlorhydria increases risk, especially for Salmonella spp. and Campylobacter spp. Achlorhydria may also result from acid-suppressing drugs.
  • Infection may arise from poorly cooked food, cooked food that has been left too long at room temperature or from uncooked food such as shellfish. Insufficient reheating of food not only fails to kill bacteria but may speed up multiplication and increase the bacterial load ingested. Even if reheating of cooked food kills bacteria, enterotoxins such as staphylococcal exotoxin, are not destroyed.

The history may well give an indication of cause. The incubation period for viruses is usually about a day, for bacillary dysentery a few hours to four days and for parasites seven to ten days.

  • Epidemics in this country are usually caused by a rotavirus but norovirus is a common cause of 'winter vomiting'.
  • Bloody diarrhoea should arouse suspicion of bacterial infection, especially E. coli O157 or, after return from an exotic location, it may be E. histolytica. Salmonella spp. is also a possibility.
  • Pyrexia in adults often suggests an invasive organism as the cause, although many other illnesses can induce fever and diarrhoea, especially in children who generally are febrile with any type of infective gastroenteritis.
  • Check temperature, blood pressure, pulse rate and and respiratory rate.
  • Perform a thorough abdominal examination, particularly to consider other possible diagnoses - eg, appendicitis.
  • Assess for features of dehydration:
    • Mild dehydration: lassitude, anorexia, nausea, light-headedness, postural hypotension.
    • Moderate dehydration: apathy, tiredness, dizziness, muscle cramps, dry tongue, sunken eyes, reduced skin elasticity, postural hypotension (systolic blood pressure >90 mm Hg), tachycardia, oliguria.
    • Severe dehydration: profound apathy, weakness, confusion (leading to coma), shock, tachycardia, marked peripheral vasoconstriction, systolic blood pressure <90 mm Hg, oliguria or anuria.
  • Stool investigations - microscopy (include ova, cysts and parasites), culture and sensitivity:
    • A stool sample should be sent for microbiological investigation if: 
      • There is blood and/or mucus in the stool.
      • The patient is immunocompromised.
    • Sending a stool sample should be considered if: 
      • The patient has recently been abroad to anywhere other than western Europe, North America, Australia or New Zealand.
      • The diarrhoea has not improved by day seven.
      • There is uncertainty about the diagnosis of gastroenteritis.
  • Unwell patients may need blood tests - eg, FBC, renal function and electrolytes.
  • Other tests will depend on the clinical scenario - eg, bowel distension requires imaging.

Not all diarrhoea or vomiting is gastroenteritis and other causes must be considered. The following list is far from complete; however, it gives some other causes of diarrhoea or vomiting but not usually both. See also separate article Chronic Diarrhoea in Adults.

Both dysentery and food poisoning are notifiable diseases. The laboratory may report the isolation to the relevant authority but it is better to duplicate notification than to overlook it. Notification is a statutory duty.

  • Arrange emergency admission to hospital if the patient is vomiting and unable to retain oral fluids, or there are features of shock or severe dehydration.
  • Other factors when considering admission include recent foreign travel, older age, poor home circumstances and low level of support, fever, bloody diarrhoea, abdominal pain and tenderness, faecal incontinence, diarrhoea lasting more than ten days, co-existing medical conditions and drug therapy (eg, systemic steroids, angiotensin-converting enzyme (ACE) inhibitors, diuretics).

The aims of management may be summarised as to identify the extent of dehydration and to treat accordingly and to educate patients in the management and prevention of gastroenteritis - eg, hand washing.

  • There is little evidence on the use of oral rehydration salt (ORS) solution in adults in developed countries. For adults able to maintain their fluid intake, ORS solution does not provide any benefits in terms of reducing the duration of diarrhoea or the number of stools. ORS solution should be used as a treatment option in people who are frail or very elderly
  • Consumption of solid food should be guided by appetite. The person should eat small, light meals and avoid fatty, spicy, or heavy food. There is little evidence on any benefit of fasting or dieting for the treatment of acute diarrhoea.
  • Measures to prevent spread of infection - eg, hands should be washed thoroughly, towels and flannels should not be shared, soiled clothing and bedlinen should be washed separately from other clothes, at the highest temperature they will tolerate, and toilet seats, flush handles, wash hand basin taps, surfaces and toilet door handles should be cleaned at least daily with hot water and detergent.
  • Advise exclusion from work or other institutional settings until at least 48 hours after the person is free from diarrhoea and vomiting. Longer periods of exclusion may be required.
  • Antidiarrhoeal drugs are not usually necessary for the management of gastroenteritis. Antimotility drugs may be useful for symptomatic control in adults with mild-to-moderate diarrhoea - for example, if quicker resolution of diarrhoea would enable the person to continue essential activities. Loperamide is the antimotility drug of choice. Antimotility drugs should be avoided if there is blood and/or mucus in the stools, or high fever.
  • Antibiotics are not recommended for adults with acute diarrhoea of unknown pathology but may be appropriate when gastroenteritis is due to a known bacterial or protozoal cause.
  • Anti-emetics are not usually necessary for the primary care management of gastroenteritis.

The risk of complications from gastroenteritis is greatest at the extremities of life, in people with concurrent chronic disease and in those who are immunocompromised. Complications include:

  • Dehydration and electrolyte disturbance.
  • Haemolytic uraemic syndrome (HUS), which is rare. HUS is characterised by acute kidney injury, haemolytic anaemia and thrombocytopenia. It occurs mostly in young children and the elderly.
  • Reactive complications - eg, arthritis, carditis, urticaria, erythema nodosum, conjunctivitis and Reiter's syndrome. They are associated with Salmonella spp., Campylobacter spp., Yersinia enterocolitica and Shigella spp. infections. There are usually no reactive complications associated with viral or parasitic gastroenteritis.
  • Systemic invasion by Salmonella spp. may cause endovascular infections and localised infections in bones, joints, meninges, or in the gallbladder.
  • Toxic megacolon caused by fulminant colitis is rare.
  • Guillain-Barré syndrome is associated with a number of viruses, especially cytomegalovirus (CMV), but Campylobacter jejuni has been the most commonly isolated pathogen in several studies.[2] 
  • Malnutrition.
  • Intractable diarrhoea: may (rarely) require long-term parenteral nutrition.
  • Irritable bowel syndrome
  • Secondary lactose intolerance
  • Reduced absorption of drugs such as anticonvulsants or oral contraceptives may occur.

Infants, the elderly and those with immunological compromise are more likely to have more severe disease and to require admission to hospital for rehydration. In severe cases hypovolaemic shock and even death can occur.

  • Usually there is an uneventful recovery. Risk is greatest at the extremes of life and in those with immunocompromise. In England and Wales between 2001-2006, 20% of deaths in persons >65 years of age caused by infectious intestinal disease other than Clostridium difficile were associated with norovirus infection.[3] 
  • In developing countries, gastroenteritis is a leading cause of death. In November 2014, the total reported number of deaths in West Africa due to the Ebola virus was 5,420.[4] 
  • Meats should be properly cooked. Vegetables and salads should be thoroughly washed before eating.
  • Uncooked meats should be kept separate from cooked and ready-to-eat food, to avoid cross-contamination.
  • Chopping boards, knives and other utensils should be washed thoroughly in hot soapy water immediately after handling any raw meat.
  • Hands should be washed before handling different food items and eating or drinking and after going to the toilet or handling pets. Effective use of hand washing could prevent many cases.[5] 

Further reading & references

  1. Gastroenteritis; NICE CKS, August 2014 (UK access only)
  2. Tam CC, Rodrigues LC, Petersen I, et al; Incidence of Guillain-Barre syndrome among patients with Campylobacter infection: a general practice research database study. J Infect Dis. 2006 Jul 1;194(1):95-7. Epub 2006 May 26.
  3. Harris JP, Edmunds WJ, Pebody R, et al; Deaths from norovirus among the elderly, England and Wales. Emerg Infect Dis. 2008 Oct;14(10):1546-52.
  4. Ebola Outbreak in West Africa; Centres for Disease Control and Prevention (CDC), 2014
  5. Freeman MC, Stocks ME, Cumming O, et al; Hygiene and health: systematic review of handwashing practices worldwide and update of health effects. Trop Med Int Health. 2014 Aug;19(8):906-16. doi: 10.1111/tmi.12339. Epub 2014 May 28.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
2180 (v25)
Last Checked:
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