What is bile acid malabsorption, and how is it treated?

Bile acid malabsorption is failure to reabsorb bile acids in the terminal ileum (e.g. after ileal resection or Crohn's), so excess bile acids enter the colon and stimulate secretion, causing watery diarrhoea. It is treated with bile acid sequestrants such as cholestyramine.

Clinical relevance. Recognising bile acid malabsorption directs treatment to sequestrants and monitoring for B12 deficiency.

More Detail

Bile acid malabsorption

Bile acid malabsorption is a common and treatable cause of chronic secretory diarrhoea.

Mechanism

• Bile acids are normally reabsorbed in the terminal ileum.
• When this fails (ileal disease/resection - e.g. Crohn's - or idiopathic), excess bile acids reach the colon and stimulate water and electrolyte secretion.
• The result is a secretory, watery diarrhoea.

Treatment

• Bile acid sequestrants such as cholestyramine (or colesevelam) bind bile acids and relieve diarrhoea.
• Treat any underlying cause.

Note

• Loss of terminal ileal function also impairs vitamin B12 absorption - monitor for deficiency.