What is diarrhoea?

Diarrhoea is defined as the passage of abnormally loose or liquid stools. Diarrhoea is very common and usually not serious. Prolonged diarrhoea may lead to excess losses of fluid, salts, and nutrients and may cause dehydration, particularly in young children and the elderly.

When the intestines are functioning normally, food and fluids pass from the stomach into the small intestine and then into the colon. The small intestine contracts in waves called peristalsis and gently pushes the food along through the bowel. The small intestine and colon absorb the nutrients and water that the body needs from the food. The remaining matter is formed into stools and enters the rectum for elimination from the body.

There are several ways in which abnormal functioning of the gastrointestinal tract results in diarrhoea:

  • The lining of the bowel becomes irritated and too much fluid is secreted into the bowel e.g. gastroenteritis and some laxatives.
  • The normally slow, wavelike contractions can become hyperactive, moving food and fluids too quickly for the bowel to absorb fluid e.g. anxiety and IBS.
  • More liquid is drunk than the bowel can cope with e.g. drinking too much beer.


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