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. Always ask about recent travel - see traveller's diarrhoea for further information.

• 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 industrialised 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.

In children the commonest cause is rotavirus. Norovirus is gaining in importance but rotavirus identification is still about 4 times as common.

Risk factors

• Poor personal hygiene and lack of sanitation increase the incidence.
• A compromised immune system leaves the patient vulnerable to gastroenteritis e.g. AIDS.
• 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".
• Bloody diarrhoea should arouse suspicion of bacterial infection, especially E. coli O157 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.

Signs

• Check for signs of dehydration e.g. moisture of mucous membranes, capillary refill time, blood pressure, pulse drop, presence of postural hypotension.
• 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.
• If the abdomen is distended, listen for bowel sounds.

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
• Emesis gravidarum or, in late pregnancy, pre-eclampsia/eclampsia
• Inflammatory bowel disease
• Addison's disease

• Stool investigations - microscopy (include ova, cysts and parasites), culture and sensitivity.
• Unwell patients may need blood tests e.g. FBC and U&E.
• Other tests will depend on the clinical scenario e.g. bowel distension requires imaging.

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 summarised as:

• Identify extent of dehydration and treat accordingly.
• To educate patients in the management and prevention of gastroenteritis e.g. hand washing.

Rehydration

• Mild dehydration - will usually only require oral rehydration with fluids or oral rehydration therapy.
• Moderate to severe rehydration may require admission to hospital for intravenous rehydration.
• The threshold for admitting infants and the elderly should be low.
• 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. These include:
  • Paralytic ileus or marked abdominal distension means that oral fluids will not be absorbed.
  • Inability to drink.
  • 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 and 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 which will worsen dehydration.

Nutrition

• In the early stages it is common for a loss of appetite to occur.
• Once their 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.

Drugs

• In most types of gastroenteritis, antibiotics do not shorten the illness but may prolong the carrier stage.² They may be used in the severely ill, especially the immuno-compromised.³
• If gastroenteritis is severe and community-acquired, there may be benefit from empirical treatment with ciprofloxacin to shorten duration without increasing carrier status.⁴
• Giardiasis is treated with metronidazole.
• A Cochrane review found very poor evidence of benefit from antiemetics in children and adolescents.⁵ 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.

• 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.
• 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.⁶
• IBS may follow gastroenteritis.
• Poor absorption of drugs such as anticonvulsants or oral contraceptives may occur.

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

• Poultry and meat should be well cooked, not pink in the middle. 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 raw meat and poultry.
• 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.⁷