Tauroselcholic [⁷⁵Se] Acid
Types of Bile Acid Diarrhoea
Diarrhoea caused by bile acids has historically been referred to as bile acid malabsorption; this description is, however, not entirely correct, as there different types of bile acid diarrhoea.1
- Type 1: Bile Acid Malabsorption.
In ileal disease, there is true malabsorption of bile acids. This was the original mechanism to be identified, and was initially referred to as choleric enteropathy.
- Type 2: Idiopathic bile acid diarrhoea.
Discovered in the 1970s and termed "idiopathic bile acid catharsis". Now known to be associated with defective feedback inhibition instead of malabsorption. This type is also known to be highly represented in patients with diarrhoea predominant irritable bowel syndrome (IBS-D).
- Type 3: Bile acid-induced diarrhoea
In association with other gastrointestinal pathology which may or may not contribute to its pathogenesis, most prominently postcholecystectomy and in combination with microscopic colitis.
Mechanism of BAD
Bile is stored in the gall bladder and released into the intestines when we eat. It passes through the intestines with food.2
- Normally, ~95% bile acid is absorbed in terminal ileum and recirculated.
- In patients with BAD, excess bile acids spill over into colon ➡ These bile salts pull water into the intestines ➡ diarrhoea.
Studies have shown that BAD may occur in between 33-45% of patients previously considered to have had diarrhoea predominant IBS (D-IBS) 3. The symptom most commonly described as 'chronic watery diarrhoea.5
However, if patients eat minimal fat, there will be little secreted luminal bile, and the extent of the diarrhoea can vary according to this. Patients with BAD also frequently describe bowel urgency and frequency, abdominal pain, cramps, excessive flatulence and unpredictable bowel habit and, less frequently, steatorrhoea as symptoms.6
1. Mottacki N et al. Alliment Pharmacol Ther 2016; 43 (8): 884-98.
2. Ridlon JM et al. Bile salt biotransformations by human intestinal bacteria. JLR 2006; 47: 241-59.
3. Fernández-Bañares et al. Am J Gastro 2007.
4. Wedlake L et al. Aliment Pharmacol Ther 2009; 30 (7): 707-17.
5. Pattni S. ,et al.. Aliment Pharmacol Ther 2013;38:967-76.
6. Kurien M, et al. Frontline Gastroenterology 2017;0:1-6. doi:10.1136/flgastro-2017-100808