Gastroenteritis
Gastroenteritis, or inflammation of the gastrointestinal tract, is an illness of fever, diarrhoea and/or vomiting caused by an infectious virus, bacterium or parasite. It usually is of acute onset, normally lasting less than 10 days and self-limiting.
The commonest viral causes of gastroenteritis in developed countries are rotavirus (40-50% of cases requiring hospitalisation), adenoviruses 40 and 41 (7-17% of cases), astrovirus, calicivirus, coronavirus, and Norwalkvirus.
Cytomegalovirus and herpes simplex virus can cause acute gastroenteritis in the immunocompromised host.
This is less common in developed countries. Campylobacter jejuni is responsible for 5-10% of cases, whereas Salmonella species, Shigella species, and various pathogenic types of Escherichia coli account for a small percentage.
In the developing world enterotoxigenic, enteropathogenic and enteroinvasive E. coli are important due to the sheer number of cases, whereas Shigella causes debilitating illness and has increasing resistance against cheap and readily available antibiotics. Cholera, caused by Vibrio cholerae is another important cause of acute diarrhoeal illness and subsequent death in the developing world.
Outbreaks of Giardia lamblia can cause dehydrating diarrhoea in infants, and Cryptosporidium is known to cause 1-4& of cases of acute diarrhoea in hospitalised infants.
Globally, diarrhoea caused 4.6 million deaths in children in 1980 alone, most of these in the developing world. This number has now come down significantly to approximately 1.5 million deaths annually, largely due to global introduction of proper oral rehydration therapy (Victora et al 2000).
The incidence in the developed countries is as high as 1-2.5 cases per child per year and a major cause of hospitalisation in this age group.
The main symptoms include poor feeding in infants, vomiting and fever, usually rapidly followed by diarrhoea. Viral diarrhoea usually causes frequent watery stools, whereas blood stained diarrhoea may be indicative of bacterial colitis.
The child with gastroenteritis may be lethargic and have signs of dehydration (dry mucous membranes, tachycardia, reduced skin turgor, sunken fontanelles and sunken eye balls, poor perfusion and ultimately shock.
It is important to consider infectious gastroenteritis as a diagnosis of exclusion. A few loose stools and vomiting may be the result of systemic infection such as pneumonia, septicaemia, urinary tract infection and even meningitis. Surgical conditions like appendicitis, intussusception and, rarely, even Hirschsprung's disease may mislead the clinician.
The main treatment of diarrhoeal illness in both children and adults is rehydration, i.e. replenishment of water lost in the stools. Depending on the degree of dehydration, this can be done orally with commercial or home-made rehydration fluids, or through intravenous delivery.
There is no evidence that antidiarrhoeal agents are of any benefit in gastroenteritis. Loperamide is commonly used, but will only treat the symptoms, and may even prolong the duration of the disease.
Antibiotics are of little or no use, unless persistent symptomatic colonisation (as seen in Giardia lamblia infestations) or septicaemia is present.
Dehydration is the most concerning complication of the diarrhoea caused by gastroenteritis and needs prompt rectification by a clinician if severe.
Febrile convulsions are not uncommon in children, especially with rotavirus infections.
Sugar malabsorption is the most common complication, especially in infants. This may result in reappearance of diarrhoea once milk, and hence the sugar lactose, is reintroduced into the diet.Aetiology
Viral causes
Bacterial causes
Parasites
Epidemiology
Clinical features
Differential diagnosis
Treatment
Drug therapy
Complications