Alterations in intestinal fluid movement.

Fluid loss in diarrhoea is caused by alterations in the basic mechanisms of transport both in the small intestine and in the colon. The role of blood flow is discussed with reference to anatomy and blood flow distribution, fluid transport, luminal pressure and intestinal motility. The control of intestinal fluid transport and of absorption and secretion processes by intracellular and extracellular mediators is reviewed. Treatment of disorders of fluid transport consist of fluid replacement therapy or the use of antidiarrhoeal agents with high specificity and safety, such as loperamide. The effects of interactions between loperamide and bacterial toxins, theophylline and prostaglandins on the antisecretory activity of loperamide are detailed.