Bile diarrhea is primarily caused by a problem with how your intestines absorb bile acids. This is often due to bile acid malabsorption (BAM). When your intestines don't absorb bile acids properly, they build up and irritate the colon. This irritation causes the colon to release extra water into the stool, resulting in watery diarrhea. Sometimes, this is due to overproduction of bile acids, rather than malabsorption. In other cases, there's no identifiable cause (idiopathic bile acid diarrhea).
Understanding Bile Acid Malabsorption
- Enterohepatic Circulation Disruption: Normally, bile acids circulate between your liver, intestines, and back to the liver (enterohepatic circulation). In BAM, this cycle is disrupted, leading to an excess of bile acids in the large intestine. [Source: Mayo Clinic, "Identifying diarrhea caused by bile acid malabsorption"]
- Increased Water Secretion: The excess bile acids in the colon stimulate increased water and salt secretion, causing the characteristic watery diarrhea. [Source: Patient.info, "Bile Acid Diarrhoea & Malabsorption: Causes and Treatment"]
- Chronic and Watery: BAM commonly presents as chronic diarrhea characterized by watery stools. This diarrhea might occur suddenly, even in the middle of the night, leading to accidents in some cases. [Source: Verywell Health, "Bile Acid Diarrhea and Malabsorption: Signs and Treatments"]
- Underlying Causes: While often idiopathic (no known cause), BAM can be secondary to other conditions affecting the intestines or liver. A deficiency in fibroblast growth factor 19 (FGF-19), a hormone regulating bile acid production, can also contribute. [Source: Gut and Liver, "Bile Acid Diarrhea: Prevalence, Pathogenesis, and Therapy"]
Other Causes of Diarrhea with Bile Acid Involvement
While BAM is a common cause, other conditions can also involve excessive bile acids contributing to diarrhea:
- Gallbladder disease: Gallstones obstructing the common bile duct can cause similar symptoms. [Source: Johns Hopkins Medicine, "Gallbladder Disease"]
Summary
Bile diarrhea is often linked to bile acid malabsorption (BAM), where impaired absorption of bile acids leads to excess in the colon, causing watery diarrhea. While sometimes idiopathic, underlying conditions or hormonal imbalances can also contribute. In some cases, overproduction of bile acids, rather than malabsorption, is the root cause.
