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bile acid malabsorption
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- chronic diarrhoea due to bile acid malabsorption
- diarrhoea is defined as the abnormal passage of loose or liquid stools more than 3 times daily or a volume of stool greater than 200 g/day
- diarrhoea is considered to be chronic if it persists for more than 4
weeks
- bile acid malabsorption is one of several causes of chronic diarrhoea
- bile acids are synthesised in the liver from cholesterol before being
transferred in conjugated form to the bile ducts, where they accumulate
and are stored in the gall bladder
- after a meal, the gall bladder contracts and bile acids flow into the intestinal lumen
- most of the bile acids are then reabsorbed by the distal ileum into the portal circulation and returned to the liver. The bile acids are later secreted into the bile again as part of a recycling process called enterohepatic circulation
- although a small proportion of bile acids (3%) are excreted in the
faeces, about 97% of bile acids are recycled
- bile acids are synthesised in the liver from cholesterol before being
transferred in conjugated form to the bile ducts, where they accumulate
and are stored in the gall bladder
- if there is bile acid malabsorption
- excess bile in the colon stimulates electrolyte and water secretion,
which results in chronic watery diarrhoea. Bile acid malabsorption causes
diarrhoea by one or more of the following mechanisms:
- inducing secretion of sodium and water
- increasing colonic motility
- stimulating defecation
- inducing mucus secretion
- damaging the mucosa, thereby increasing mucosal permeability
- excess bile in the colon stimulates electrolyte and water secretion,
which results in chronic watery diarrhoea. Bile acid malabsorption causes
diarrhoea by one or more of the following mechanisms:
- bile acid malabsorption has been divided into 3 types depending on aetiology:
- type 1: following ileal resection, disease or bypass of the terminal
ileum
- type 2: primary idiopathic malabsorption - type 2 bile acid
malabsorption has no known cause
- in people with type 2 bile acid malabsorption, there is a history
of diarrhoea that can be either continuous or intermittent
- in people with type 2 bile acid malabsorption, there is a history
of diarrhoea that can be either continuous or intermittent
- type 3: associated with cholecystectomy, peptic ulcer surgery, chronic pancreatitis, coeliac disease or diabetes mellitus
- type 1: following ileal resection, disease or bypass of the terminal
ileum
Although not life threatening, bile acid malabsorption can have a considerable impact on lifestyle and quality of life because the associated increased frequency of bowel motions often limits the person's ability to travel or leave the house
Treatment
After a definitive diagnosis of bile acid malabsorption, people can be treated with bile acid sequestrants that bind with bile acids in the small bowel and prevent the secretory action of bile acids on the colon
- colestyramine and colestipol are anion exchange resins that have a high affinity for bile acids in the gastrointestinal tract, and form complexes with them
- a disadvantage of colestyramine and colestipol is an unpleasant taste, which can lead to poor tolerance of and adherence to treatment. Other side effects include constipation, nausea, borborygmi, flatulence, bloating and abdominal pain
- colesevelam is a newer bile acid sequestrant that forms a polymeric gel in the gastrointestinal tract
- binds to bile acids with higher affinity than colestyramine or colestipol
- colesevelam is available in tablet form, whereas colestyramine is only available in powder form, which some people find unpleasant
The response to bile acid sequestrants varies among people who have diarrhoea due to bile acid malabsorption
- for people with Crohn's disease and ileal resection, the response to bile acid sequestrants has been reported to be 60%. In people with Crohn's disease without ileal resection, the estimate of response to bile acid sequestrants was 40% and in people with a diagnosis of IBS-D (diarrhoea predominant irritable bowel syndrome) the estimate was 70%
Reference:
Last reviewed 11/2020
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