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. Sometimes it is referred to simply as 'gastro'.

Aetiology

Viral causes

The commonest viral causes of gastroenteritis in developed countries are rotavirus (40-50% of the cases which required 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.

Bacterial causes

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.

Parasites

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.

Epidemiology

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.

Clinical features

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.

Differential diagnosis

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.

Treatment

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.

Drug therapy

Loperamide is an opioid analogue commonly used for symptomatic treatment of diarrhoea. It slows down gut motility, but does not cross the mature blood-brain barrier to cause the central nervous effect of other opioids. In too high doses, loperamide may cause constipation and significant slowing down of passage of faeces, but an appropriate single dose will not slow down the duration of the disease (Wingate et al, 2001).

Loperamide is not recommended in children, especially in children younger than 2 years of age, as it may cause systemic toxicity due to an immature blood brain barrier, and oral rehydration therapy remains the main stay treatment for children.

Antibiotics are of little or no use, unless persistent symptomatic colonisation (as seen in Giardia lamblia infestations) or septicaemia is present.

Complications

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.

References

Victora, C. G., Bryce, J., Fontaine, O., & Monasch, R. 2000, 'Reducing deaths from diarrhoea through oral rehydration therapy', Bulletin of The World Health Organization, vol. 78, no. 10, pp. 1246-1255.

Wingate D. et al. 2001. 'Guidelines for adults on self-medication for the treatment of acute diarrhoea', Alimentary Pharmacology & Therapeutics, vol. 15, no. 6, pp. 773-782.

External links

• The World Health Organisation on diarrhoea (http://www.who.int/health_topics/diarrhoea/en/)
• eMedicine Health (http://www.emedicinehealth.com/articles/5962-1.asp)