[Physiopathology of diarrhea]

Diarrhoea is defined as the daily excretion of faecal water in increased amounts. Several mechanisms may result in diarrhoea. They are: (1) increase in fluid and ions load which may exceed the maximum capacity of intestinal reabsorption; this is the "volumogenic" diarrhoea observed in Zollinger-Ellison syndrome; (2) accelerated gastrointestinal transit, notably through the colon, as in the so-called "diarrhée motrice" due to increased colonic motility; (3) osmotic diarrhoea due to ingestion of nonabsorbable solutes, as in malabsorption syndromes; (4) secretory diarrhoea with disorder of NaCl transport in the intestine as its main abnormality; this diarrhoea may be of bacterial, endocrine or other origin; (5) diarrhoea consecutive to morphological abnormalities of the small bowel and/or colon; it is often due to several of the above mechanisms, to which must be added exudation of blood, mucosities and proteins in the intestine.