Gastroenteritis in Adults and Older Children

Gastroenteritis is a non-specific 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.

The issue of gastroenteritis in children of a younger age is covered elsewhere as they tend to pose different problems and risks from adults and older children.

• Gastroenteritis is caused by a variety of viral, bacterial, and parasitic pathogens.
• In the UK, it is estimated that infectious enteritis affects about 1 in 5 people per year of whom only 1 in 6 presents to a general practice.¹
• Worldwide, there are more than 1 billion cases and at least 4 million deaths per year attributed to diarrhoea.
• Virus infections cause 30-40% of gastroenteritis cases in industrialized countries. The figure is higher for children. The causative agent for most cases of gastroenteritis is never isolated and the responsible agent never diagnosed. Management is not usually dependent upon cause.

Risk factors

Poor personal hygiene and lack of sanitation increase the incidence. A compromised immune system leaves the patient vulnerable to gastroenteritis. Patients with AIDS are especially at risk. Achlorhydria increases risk, especially for Salmonella and Campylobacter. 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.

Symptoms

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 4 days and for parasites 7 to 10 days.

• Epidemics in this country are usually caused by a rotavirus but Norovirus is a common cause of "winter vomiting"
• Ask about recent travel abroad.
• If a number of people who ate together are affected, the incubation period may give an indication of the responsible organism.
• If diarrhoea lasts for more than a fortnight, the aetiology is likely to be different from that of shorter duration.
• Bloody diarrhoea should arouse suspicion of bacterial infection, especially E. coli 0157 or after return from an exotic location it may be Entamoeba histolytica. Salmonella 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 for signs of dehydration. Both small children and the elderly are more vulnerable.
• Always perform an abdominal examination. Appendicitis can start with gastroenteritis and even if there is no sign of an acute abdomen at the time of the examination, be prepared to repeat the examination as signs can appear later. Furthermore, if you record negative findings for an acute abdomen and it later transpires that it is appendicitis, your position is sound.
• If the abdomen is distended, listen for bowel sounds.

These incubation periods should not be taken too rigidly. There is enormous variation between different authorities with regard to the incubation period for any given infective agent. It is likely that the incubation period is dependent upon the infecting dose and the resistance of the host.

• Rotavirus has an incubation period of 1 to 3 days and a duration of 3 to 8 days. It occurs in outbreaks with small children most at risk.
• Norwalk virus, now called Norovirus, is another major cause of gastroenteritis. Although relatively mild, Norovirus illness can occur at any age because immunity to it is not long-lasting. The syndrome is commonly referred to as "winter vomiting disease" due to its seasonality and typical symptoms. Outbreaks of Norovirus gastroenteritis are common in semi-closed environments such as hospitals, nursing homes, schools and cruise ships.
• Salmonella gastroenteritis has an incubation period of 8 to 48 hours and lasts 2 to 5 days. Salmonella gastroenteritis is not to be confused with typhoid and paratyphoid fever. Both forms of Salmonella have their own articles.
• Campylobacter has an incubation period of 2 to 5 days and illness lasts 2 to 5 days. Risk is from undercooked meat.
• Cryptosporosis has an incubation period of 1 week. Risks are from unpasteurised milk and untreated water.
• Cyclospora has an incubation period of a week and symptoms from a few days to a month. Risk is water contaminated with faeces.
• Giardia has an incubation period of 2 to 12 days, average 7. It lasts 2 weeks.
• E. coli is the commonest cause of traveller's diarrhoea. Symptoms usually begin within days of arrival in the region and last from 5 days to 2 weeks.
• E. coli O157 has an incubation period of 1 to 7 days. It can cause bloody diarrhoea.
• Listeria monocytogenes has an incubation period of 3 weeks² but can be much longer. Risk is from soft cheeses and milk. Infection in pregnancy can cause miscarriage³ and advice is to avoid soft cheeses in pregnancy.
• Shigella incubation period is 2 to 4 days and duration 5 to 7 days. Risks are from fruit, vegetables and shellfish. This is a very serious form of gastroenteritis.
• Yersinia
• Cholera produces profuse "rice-water" diarrhoea.
• In those who have been to exotic places, amoebiasis due to Entamoeba histolytica must be considered.

Not all diarrhoea or vomiting is gastroenteritis and other causes must be considered. The following list is far from complete but gives some other causes of diarrhoea or vomiting but not usually both.

• Urinary tract infection.
• Constipation with overflow.
• Gastritis, perhaps from NSAID or alcohol abuse.
• Acute appendicitis.
• Emesis gravidarum or, in late pregnancy, fulminating pre-eclampsia.
• Irritable bowel syndrome.
• Inflammatory bowel disease.
• Intestinal obstruction.
• Laxative abuse.
• Addison's disease.

Diagnosis is often by culturing the organism from the stool. Rotavirus can be detected. Microscopy for ova or parasites.

In the hospital setting, FBC and U&E will be fundamental, but they are not usually required in primary care.

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.

Aims of management

The aims of management may be summarized as:

• To identify and treat those with moderate to severe dehydration, especially those at high risk who may need referral to hospital.
• To treat or prevent more mild dehydration.
• To educate patients in the management and prevention of gastroenteritis.
• To prevent spread.

Included in the last may be early recognition and institution of infection-control measures for:

• Acute infectious gastroenteritis
• Food poisoning
• Dysentery
• Clostridium difficile-associated disease

Non-drug

• Attention to dehydration usually requires just oral rehydration fluids. Starvation is recommended but feeding should be introduced in children as soon as vomiting subsides. Sometimes admission to hospital is required for intravenous rehydration. The threshold for admitting infants should be low but the elderly are also at risk.
• Attention to hand washing to prevent spread to others.
• Probiotics may possibly be a useful adjunct to therapy⁴ but their role is uncertain.

Most patients who have gastroenteritis do not wish to eat and there should be no pressure to do so. If appetite has returned and the patient feels hungry, this is a good sign that it is safe to resume food but start with something small and bland.

Oral rehydration is successful in at least 95% of cases but there are danger signs that indicate that intravenous therapy is required and this requires admission to hospital.

• Severe or life-threatening dehydration requires rapid intravenous rehydration with both water and electrolytes.
• Paralytic ileus or marked abdominal distension means that oral fluids will not be absorbed.
• Inability to drink may be bypassed by a naso-gastric tube but the patient is at risk.
• Very rapid stool loss (more than 15 ml/kg body weight per hour) may make it impossible for the patient to meet loss by oral intake.
• Severe, repeated vomiting is unusual. Usually, most of the oral fluid is absorbed despite vomiting, and vomiting stops as dehydration and electrolyte imbalance are corrected.
• Glucose malabsorption is unusual but in such rare cases, stool volume will increase and the stool contains large amounts of glucose. This will worsen dehydration.

Drugs

• In most types of gastroenteritis, antibiotics do not shorten the illness but may prolong the carrier stage.⁵ They may be used in the severely ill, especially the immuno-compromised.⁶
• If gastroenteritis is severe and community-acquired, there may be benefit from empirical treatment with ciprofloxacin to shorted duration without increasing carrier status.⁷
• Giardiasis is treated with metronidazole.
• A Cochrane review found very poor evidence of benefit from antiemetics in children and adolescents.⁴ The 2 drugs examined were ondansetron and metoclopramide although the latter is usually avoided in children, adolescents and young adults because of extrapyramidal effects.
• Sometimes anti-diarrhoea or anti-spasmodic drugs may be required but avoid them in children.

Return to work

When diarrhoea has settled, the vast majority are not a risk to others and may return to work with no further testing. The following need advice from Environmental Health Officers or a Consultant in Communicable Disease Control (CCDC):

• Food handlers who touch unwrapped food to be consumed raw or without further cooking.
• Health-care, nursery or other staff who have direct contact with people who are susceptible to infection or for whom a gastroenteritis would have very serious consequences. This includes simply serving food to them.
• Children under 5 years attending nurseries, play groups, nursery schools etc.
• Older children or adults with poor standards of personal hygiene including the mentally ill, handicapped or the elderly infirm.

Food handlers must be clear of symptoms for at least 48 hours and have produced a negative stool sample before return to work.

• 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.
• Haemolytic uraemic syndrome is most likely to affect small children but can occur at a later age.
• Reactive features may include arthritis, carditis, urticaria, erythema nodosum, conjunctivitis, and Reiter's syndrome.
• Salmonella can invade bones, joints, meninges, or the gallbladder.
• Toxic megacolon is rare.
• Some viruses may cause Guillain-Barre syndrome as may Campylobacter.⁸
• IBS may follow gastro-enteritis.
• Poor absorption of drugs such as anticonvulsants or oral contraceptives may be important.

Usually there is uneventful recovery with just a period of starvation and fluids only. Risk is greatest at the extremes of life and with immune compromise. In England and Wales in 2005, deaths associated with gastrointestinal infections were predominantly in the elderly.

• Poultry and meat, including burgers should be well cooked, not pink in the middle. Vegetables and salads should be thoroughly washed before eating.
• Uncooked meats kept separate from cooked and ready to eat food to avoid cross contamination.
• Hands, chopping boards, knives and other utensils should be washed thoroughly in hot soapy water immediately after handling raw meat and poultry.
• Hands should be washed before handling different food items and before eating or drinking and after going to the toilet.
• Those who are ill should not prepare or handle food.
• Everyone must wash their hands after contact with animals including pets.
• Wash hands thoroughly with soap in warm running water and dry with a clean towel or disposable paper hand towel. Effective use of hand washing could prevent many cases.⁹
• Gastroenteritis often results from a combination of contaminated foods, poor kitchen hygiene and inadequate cooking.
• Good kitchen practices including thorough cooking of potentially contaminated foods, especially chicken, should be applied in the home and by the chef. The Chief Medical Officer advises against recipes with uncooked or lightly cooked eggs. Adequate cooking of eggs, until the yolk is set, kills salmonellas. Take care that food does not become contaminated after cooking.
• For those travelling to high risk areas a daily dose of ciprofloxacin¹⁰ does have benefit. Rifaximin looks promising¹¹ but is not yet in the BNF. It is a new antibiotic that is not absorbed. Co-trimoxazole may be a suitable alternatives for children. Antibiotics and immunisation may help but for travellers' diarrhoea there is no substitute for attention to hygiene and being sensible about what is ingested.¹¹