Introduction:
Bile acid diarrhea (BAD) can be caused by gastrointestinal diseases, such as Crohn's disease (CD) or post-cholecystectomy, but it can also be due to unknown etiology (primary BAD). Bile acid malabsorption (BAM) in the small intestine causes BAD. About 95 percent of bile acids (BAs) are absorbed into the ileum (a large part of the small intestine) and brought back to the liver through enterohepatic circulation in healthy people. Suppose bile acid (BA) reabsorption is decreased, or bile acid concentrations in the small intestine exceed the ileum's resorptive capacity. In that case, elevated levels of bile acids move into the large intestine and, by stimulating colonic motility and secretions, cause diarrhea. The terms bile acid malabsorption and bile acid diarrhea are frequently used interchangeably.
Bile acid diarrhea (BAD) is known to cause a wide range of gastrointestinal symptoms, such as urgency, excessive flatulence, abdominal pain, and fecal incontinence. BAD is estimated to affect 1 percent of the population, with 10 to 30 percent of patients being misdiagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D).
What Is the Classification of Bile Acid Diarrhea (BAD)?
BAD is categorized into three main types:
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Type 1 results from ileal inflammation or resection, with Crohn's disease (CD) being the most common cause.
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Type 2 is idiopathic (unknown cause) or primary BAD.
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Type 3 is secondary to other gastrointestinal diseases (cholecystectomy, small bowel intestinal bacterial overgrowth, coeliac disease, chronic pancreatitis).
BAD is present in more than 90 percent of patients with post-cholecystectomy diarrhea and more than 90 percent with terminal ileal resection.
What Is the Pathophysiology of BAD?
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Type 1 BAD: The loss of the primary site for active and passive bile acid reabsorption due to ileal resection or disease causes increased BA delivery to the large intestine
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Type 2 BAD: The leading cause is an elevated production of BA due to malfunctioning negative feedback on BA synthesis. Excessive BA delivery to the ileum surpasses its reabsorption capacity, resulting in elevated levels of BAs in the colon and causing diarrhea. Type 2 BAD may also occur from rapid small bowel transport that bypasses active BA reabsorption, though this is less likely. In addition, fibroblast growth factor (FGF-19) is a regulator of BA synthesis in the liver, and its absence or reduction may result in increased BA synthesis and, as a result, BAD.
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Type 3 BAD: Bacterial overgrowth in the small bowel causes elevated or altered bacterial deconjugation of BAs and decreases the effectiveness of BA reabsorption. By increasing intestinal motility, other gastrointestinal diseases may decrease the duration for ileal reabsorption of BA and the time for bacterial conversion of primary to secondary BAs, lowering BA reabsorption efficiency.
How Is BAD Diagnosed?
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However, the diagnosis of BAD is frequently overlooked because of challenges in obtaining an appropriate diagnostic test, and patients are subsequently diagnosed with IBS.
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The four most analyzed choices for BAD:
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The radiolabelled 23-seleno-25- homotaurocholic acid (SeHCAT) test.
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Evaluation of fecal bile acids (FBA).
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Serum-C4 measurement.
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A trial of bile acid sequestrants is diagnosed.
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Other alternatives include:
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Measuring serum FGF19.
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14C-glycocholate breath and stool tests.
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Urine-2-proponol.
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The 75 selenium-homotaurocholic acid test is the gold standard diagnostic test (75 SeHCAT). Selenium-75 homocholic acid taurine is a synthetic analog of taurocholic acid taken as a capsule after fasting overnight.
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After three hours, an initial gamma measurement is made, which is compared to the gamma measurement after seven days. Finally, the obtained two measurements are divided to calculate the percentage of 75 SeHCAT retained.
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The SeHCAT molecule travels through the same enterohepatic circulation as natural BAs, allowing researchers to track its retention and loss.
What Are the Effects of BAD on the Quality of Life?
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BAD symptoms can be severely debilitating and have a negative impact on a patient's quality of life (QoL). Poor QoL has been linked to disability, the usage of healthcare resources, and clinical response to therapy.
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According to a recent study on BAD patient symptoms and outcomes, more than 80 percent of patients experienced depression, isolation, helplessness, and low self-esteem.
What Is the Treatment of BAD?
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The standard therapy for BAD includes bile acid sequestrants, the exchange of anions that bind to bile acids in the intestine with high affinity, creating an insoluble complex that is excreted in the feces, avoiding reabsorption into the enterohepatic circulation.
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Cholestyramine, Colestipol, and Colesevelam are the three drugs in use. However, Cholestyramine is frequently used as the first-line treatment.
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Patients may consider the treatment too effective, especially if they have previously received large doses for cholesterol reduction. While their stools may become more solid and less regular, they may experience constipation, bloating, abdominal cramps, or nausea. As a result, it is essential to titrate the dosage until it is well tolerated.
What Are the Risks of Bile Acid Sequestrants(BAS)?
Some of the side effects of bile acid sequestrants include:
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Flatulence.
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Constipation.
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Nausea and unpleasant taste.
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These may reduce patient compliance, contributing to the observed level of ineffectiveness and making it difficult to assess treatment efficacy fully.
Conclusion:
There are several assuring methods for diagnosing BAD; each requires further field evaluation before being considered as a replacement for SeHCAT. Because of the considerable under-diagnosis of patients, the availability of relatively simple and reasonably effective treatment for BAD and improved quality of life in these patients should be a primary concern. Effective and readily available methods of diagnosis should minimize missed diagnoses, increase the initiation of appropriate treatment, and improve patient quality of life of t
