Bowel symptoms including diarrhoea can be produced when excess
bile acids (BA) are present in the colon. This condition, known as
bile acid or
bile salt malabsorption, has been under recognized, as the best diagnostic method, the (75)Se-homocholic
acid taurine (
SeHCAT) test, is not available in many countries and is not fully utilized in others. Reduced
SeHCAT retention establishes that this is a complication of many other
gastrointestinal diseases. Repeated studies show
SeHCAT tests are abnormal in about 30% of patients otherwise diagnosed as diarrhoea-predominant
irritable bowel syndrome or functional diarrhoea, with an estimated population prevalence of around 1%. Recent work suggests that the condition previously called idiopathic
bile acid malabsorption (BAM) is not in fact due to a defect in absorption, but results from an overproduction of BA because of defective feedback inhibition of hepatic
bile acid synthesis, a function of the ileal
hormone fibroblast growth factor 19 (FGF19). The approach to treatment currently depends on binding excess BA, to reduce their secretory actions, using
colestyramine,
colestipol and, most recently,
colesevelam.
Colesevelam has a number of potential advantages that merit further investigation in trials directed at patients with
bile acid diarrhoea.