Chapter 15 ACUTE DIARRHOEA

KEY POINTS

• Acute infectious diarrhoea is common worldwide and is responsible for significant patient hospitalisation and mortality.

• Acute diarrhoea is defined as an increase of stool frequency (greater than three stools per day or at least 200 g of stool per day) lasting less than 14 days.

• The principal recognised causes of diarrhoea include viruses, bacteria and protozoa.

• Assessment should focus on the severity of illness, need for rehydration and the identification of the aetiology of the illness on the basis of history and clinical findings.

• Management of acute diarrhoea should include fluid resuscitation, empirical antibiotics or specific antibiotic therapy if the causative organism is isolated.

DEFINITION

Diarrhoea is a leading cause of death worldwide. It is defined as an alteration in normal bowel habit characterised by an increase in volume, water content and frequency of bowel movements, and must have a weight of at least 200 g stool per day.

A more practical approach for the definition of diarrhoea is the presence of three or more loose watery stools per day or a distinct change in a person’s normal bowel routine. A working definition of diarrhoea is based upon the duration of symptoms:

• Acute—less than 14 days in duration

• Persistent—more than 14 days but less than 30 days in duration

• Chronic—more than 30 days in duration.

PATHOPHYSIOLOGY

The symptoms of acute diarrhoea vary according to the portion of the intestine that is involved in the disease process. Infectious diarrhoea is often associated with symptoms of nausea, vomiting and abdominal cramps.

The small intestine functions as a fluid and enzyme secretory organ and nutrient absorbing region. Therefore, a pathogen affecting this region will produce symptoms of watery diarrhoea, which is usually of large volume and is associated with abdominal cramping, bloating and weight loss.

The colon is involved in absorption of fluid and salt, as well as excretion of potassium. When this area is involved, the symptoms include frequent, regular small volume, often painful defecation. Fever and bloody mucoid stools are common.

AETIOLOGY

Infectious and non-infectious causes may be responsible for acute diarrhoea (Table 15.1).

TABLE 15.1 Agents that commonly cause acute diarrhoea

Bacteria • Campylobacter • Salmonella • Shigella • Escherichia coli O157:H7 • Clostridium difficile	Viruses • Caliciviruses (norovirus and Norwalk-like and related viruses) • Rotavirus • Adenovirus types 40 and 41 • Astrovirus
Protozoa • Cryptosporidium • Giardia • Entamoeba histolytica

Infectious causes include bacteria, viruses and protozoa.

Bacteria

• Campylobacter: most common bacterial cause usually from poultry, meat, dairy products and contaminated water.

• Salmonella: usually from poultry and livestock.

• Shigella: highly contagious spreads from person to person.

• Escherichia coli: O157:H7: usually from contaminated meat, can be associated with haemolytic uraemic syndrome.

• Clostridium difficile: major cause of nosocomial colitis occurring after antibiotic-induced alteration of bowel flora and subsequent proliferation of an endogenous strain. Can also be contagious.

Viruses

Viruses cause the vast majority of all cases of acute diarrhoea.

• Caliciviruses (norovirus/Norwalk): can be detected in vomitus and faeces as compared with bacterial causes of diarrhoea (which is usually shed in faeces alone). Contaminated food or water are the usual primary causes but person-to-person contact is a secondary cause.

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