Diarrhoeal diseases are a major public health problem in developing countries, leading to morbidity and mortality, particularly in the young, elderly and malnourished. It is estimated that acute diarrhoea accounts for between three and four million deaths annually worldwide.
In chronic diarrhoea, daily stool weights can vary from 200g to 1500g, but in acute diarrhoea, daily stool weights can vary from 1kg to 20kg, the higher amounts being seen in cholera.
Causes of diarrhoea
Diarrhoea is often caused by bacterial, parasitic or viral infections, although some patients experience diarrhoea after a course of antibiotics, particularly the penicillin and tetracycline groups, which alter the intestinal bacterial environment (gut flora).
Chronic diarrhoea can be a symptom of disorders including lactose intolerance, coeliac disease, irritable bowel syndrome, inflammatory bowel disease such as Crohn's disease, intestinal neoplasm, excess alcohol consumption and laxative use.
Where diarrhoea is caused by bacteria, it is usually classified as toxigenic or invasive. Toxigenic diarrhoea (such as cholera, enterotoxic E coli and Staphylococcus aureus) occurs where the bacteria secrete an enterotoxin that quickly irritates the gut mucous membrane, leading to symptoms.
Invasive bacteria (such as Shigella and Salmonella) invade the bowel wall, increasing its permeability. Viruses may also cause diarrhoea, particularly adenovirus and rotavirus.
Parasites commonly causing diarrhoea, particularly in those who travel to parts of the world where water may be contaminated, include Giardia lamblia and tapeworm.
Diagnosis and management
Symptoms of diarrhoeal disease include frequent watery stools, anorexia, nausea and vomiting, abdominal pain, fever, dehydration and drowsiness - from intoxication or dehydration.
Complications of acute diarrhoea arise mainly from dehydration and loss of electrolytes. This may be further exacerbated if the patient is also vomiting or sweating profusely.
In chronic diarrhoea, nutritional status may also be more generally compromised as nutrients are not absorbed effectively through the intestinal wall, leading to secondary complications such as iron-deficiency anaemia and osteoporosis.
Depending on the cause, diarrhoea can usually be treated at home, with patients being advised to drink plenty of fluids to correct dehydration and electrolyte imbalance. Sachets of oral rehydration mix can be effective for this purpose. Patients should also be advised to maintain good hygiene, especially in preparing food.
In more severe cases, management involves diagnosis and treatment of the underlying disorder, IV replacement of fluids and electrolytes, antidiarrhoeal drugs, and dietary supplements to correct nutritional deficiencies if the condition has been present for some time.
More serious symptoms include pus or blood in the stools, reduced or absent urination and fever, all of which should be investigated further.
In some cases of chronic and intractable diarrhoea a low-residue diet may be used -avoiding fibre - but in other patients, an increase in the fibre content of the diet is beneficial.
Successful treatment depends on elucidating the underlying cause, by means of a good medical history and physical examination, along with blood and stool sample tests.
Travellers' diarrhoea affects an estimated 30 to 80 per cent of travellers.
It is typically caused by the different viruses and bacteria at the destination, by food and drink that has been contaminated or contamination of drinking water.
Many cases can be avoided by practising good hygiene and using the basic 'cook it, boil it, peel it or leave it' advice if travelling to destinations where there is a known high risk.
Drinking treated or bottled water and avoiding ice made from untreated water can reduce risk. Using an antiseptic hand lotion or wipes can also be helpful, especially when in transit.
Most cases of travellers' diarrhoea resolve within a few days without medical treatment, but rehydration mixes made up with uncontaminated water, some solid foods, rest and possibly an antidiarrhoeal drug can be taken.
Further medical intervention is required where symptoms include blood in the stools, fever, gastric pain and dehydration, especially in infants, young children and the elderly.
Probiotics are preparations of microbes that are thought to have a beneficial effect on the health of the host, owing to their potential to affect the balance of colonic microflora.
Some studies have shown benefits for the protection from and the treatment of acute infectious diarrhoea.
A systematic review recently showed a significant reduction in the duration and severity of diarrhoea, although the most effective strain of probiotic and the effective dose is unclear.
- Dr Phillips is national PR officer at the British Dietetic Association