Diarrhoea is the passage of 3 or more loose or liquid stools per day, or more frequently than normal for the individual. It is usually a symptom of gastrointestinal infection, which can be caused by a variety of bacterial, viral and parasitic organisms. Infection is spread through contaminated food or drinking-water, or from person to person as a result of poor hygiene (Figure).
Diarrhoea is an increase in frequency, volume or fluidity of stools
It may be secretory diarrhea which results when excess water and electrolytes are actively transported into the lumen of the intestines. Osmotic diarrhoea results when water is retained in the intestinal lumen by osmotically active agents. The rate of transit through the gut determines the time available for intestinal absorption of water and very rapid transit can result in diarrhea. The maximum absorptive capacity of the colon is only 4 l/day, so if volumes of fluid greater than this enter the small intestine, diarrhea will result even though the colonic function is normal. The small intestine secretes about 1 l/day of fluids, but this can increase to as much as 20 l/day under certain conditions. Thus large volume diarrhoea indicates dysfunction of the small intestine.
Loss of excessive body water through diarrhoea could lead to dehydration and electrolyte loss, especially loss of potassium. Both need to be replaced in order to avert a life threatening situation.