What Is Bile Acid Malabsorption?

Definition:

Bile acid malabsorption (BAM) is a condition in which bile acids are not properly processed within the digestive system, resulting in symptoms of chronic diarrhea.

To best understand BAM, it helps to understand how digestion is supposed to work. Your gallbladder is responsible for releasing bile acids into the small intestine for the digestion of fats. When BAM is present, these acids are not well absorbed and therefore excessive amounts are flushed into the large intestine.

The effect of bile acids on the large intestine is an increase fluid production, resulting in watery stools and a speeding up of intestinal motility, both of which result in symptoms of diarrhea.

BAM is characterized by type, depending on its cause:

  • Type 1: Secondary to ileal (small intestine) disease or resection.
  • Type 2: Idiopathic or primary - cause is unknown.
  • Type 3: Secondary to all other types of gastrointestinal disease.

Diagnosis of BAM

BAM is diagnosed definitively through the use of a procedure called the 75SeHCAT scan. This is a nuclear medicine test in which a patient is given a capsule to swallow orally and then undergoes a full body scan. A repeat scan is scheduled seven days later. The capsule contains SeHCAT, which is used to assess the ability of the small intestine to retain bile acids. A retention rate lower than 15% is considered to be indicative of the presence of BAM.

This procedure is not available in the United States.

When the 75SeHCAT scan is not available, physicians may diagnose the condition based on the results of a trial of BAM medication.

Treatment of BAM

BAM is treated with a class of medication known as bile acid sequestrants or binders. These medications appear to work on the symptoms of BAM by binding to the acids and thereby reducing their effects on the large intestine.

These are the current members of this class:

Sources:

Borghede, M., et.al. "Bile acid malabsorption investigated by selenium-75-homocholic acid taurine (75SeHCAT) scans: Causes and treatment responses to cholestyramine in 298 patients with chronic watery diarrhoea" European Journal of Internal Medicine 2011 22:e137–e140.

Pattni, S. & Walters, J. "Recent advances in the understanding of bile acid malabsorption" British Medical Bulletin 2009 92:79-93.

Wedlake, L., et.al. "Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome" Alimentary Pharmacology and Therapeutics 2009 30:707-717.

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