General Health

What Is Bile Acid Malabsorption?

A GI condition, bile acid malabsorption causes chronic diarrhea. Here’s what you need to know, including symptoms, causes, and treatments.

by玛丽格雷斯·泰勒（Marygrace Taylor） Health Writer

December 14, 2022

Medical Reviewer

David Padua, M.D.

GettyImages/comzeal

December 14, 2022

Medical Reviewer

David Padua, M.D.

If you’ve beendealing with chronic gastrointestinal (GI) symptoms, you’re probably keen on getting a diagnosis. Though relatively rare, one possibility—if you have chronic diarrhea—is bile acid malabsorption, a GI disorder that can take a long time to diagnose. It happens when bile travels to parts of the lower GI tract where it doesn’t typically belong. About 1% of the Western population is estimated to be affected; however, the condition is likely underdiagnosed,research shows。

While not life-threatening the resulting chronic diarrhea and its associated discomfort and exhaustion can take a significant toll on your quality of life. Here’s a closer look at how the problem develops and who’s most likely to be affected, how to get diagnosed, and treatment options to help you feel better.

The Role of Bile in Digestion

Bile is a greenish-yellow fluid that made by the liver, and facilitates the breakdown of lipids, or fats during digestion. It consists mostly of cholesterol, along with some digestive acids and a smattering of waste products. When food containing fat makes its way into the small intestine during digestion, bile is released by the gallbladder to break the fats down into smaller, more absorbable components.

After this important job is complete, most of the released bile is reabsorbed by the ileum (the lower portion of the small intestine that connects to the colon) and stored in the liver, so it can be used again the next time fat needs to be digested. “It’s effectively a recycling process,” saysAshkan Farhadi，医学博士，位于加利福尼亚河谷的纪念橙海岸医疗中心的胃肠病学家。

It’s normal for a very small amount of bile to escape reabsorption, travel down to the colon, and eventually end up in stool. (In fact, bile is what gives stool it’s dark brown color.) But in someone with bile acid malabsorption, large amounts of bile spill into the colon instead of being reabsorbed by the small intestine. This stimulates the secretion of electrolytes and water, which causebowel movementsto become loose and fluid-like. Chronic watery diarrhea results.

Causes of Bile Acid Malabsorption

Often, BAM occurs when the ileum isn’t working the way it should or has sustained some kind of damage. “That can disturb the bile recycling system, so more bile can get into the colon,” Dr. Farhadi explains.

回肠问题可能出现多种原因，包括克罗恩病，腹腔疾病或小肠细菌过度生长（SIBO）等胃肠道疾病。它也可能是某些GI手术的副作用。“如果某人的小肠中有很大一部分，BAM可能会发生。”塞弗丁·哈基姆（Seifeldin Hakim），医学博士休斯顿纪念赫尔曼医学集团的胃肠病学家。胰腺功能不全（当您的胰液不足时digestive enzymes) can lead to BAM too, possibly by causing bile to bind to undigested dietary components that then get excreted in a person’s stool,researchers have theorized。

Often, though, doctors can’t pinpoint an underlying cause of damage to the ileum. It most often occurs in people withirritable bowel syndromewith diarrhea (IBS-D), and might be related toinflammationfrom the IBS,findings suggest。

胆汁酸吸收不良的类型

Experts have classifiedfour types of bile acid malabsorption. Which variety a person has depends on the suspected cause of their BAM.

Type 1: Secondary Bile Acid Malabsorption

The most common type, secondary BAM happens because of a known problem with the ileum. Typical culprits areCrohn’s disease或手术gallbladder或去除回肠的一部分。包括化学疗法或腹部或盆腔辐射在内的医疗治疗也可能导致继发性BAM。

类型2：主要BAM

Sometimes called idiopathic BAM, type 2 happens when the cause of a person’s bile acid malabsorption isn’t known. It often occurs in people who have functional diarrhea disorders such as IBS-D,studies show。

类型3：由其他条件引起的BAM

其他胃肠道问题，例如乳糜泻或小肠细菌过度生长（SIBO）可能会导致3型。胰腺功能不全，一个人没有足够的某些消化食物所需的酶。

Type 4: Bile Acid Malabsorption Caused By Metformin

In some cases, the diabetes drug metformin can cause excessive bile production, which can then lead to bile acid malabsorption.

胆汁酸吸收症状

Chronic, watery diarrhea is the hallmark symptom of BAM. It’s not uncommon to experience side effects of that diarrhea as well, Dr. Farhadi notes. These could include:

• 脱水

• 头晕

• 疲劳

• 头痛

• Weight loss

People with BAM often have other GI symptoms as well, including:

• Abdominal discomfort

• Bloating

• Cramping

• 紧迫性

Diagnosing Bile Acid Malabsorption

BAM can be tough to diagnose. “We don’t have great tests for it,” says Dr. Hakim. And because it’s not that common, it’s not typically the first condition GI doctors think of for most patients who are dealing with diarrhea (unless a patient has had GI surgery or Crohn’s, since those are two of the most typical causes of BAM).Studies reportthat it takes nearly half of patients five years to get diagnosed with BAM. Many are firsttold that they have IBS。这些是医生可以用来帮助诊断的一些工具。

Fecal Bile Acid Tests

这些观察在吃一顿很高的脂肪饭后48小时后，一个人的粪便中的胆汁酸数量。但是，准确率仅在66％至79％之间，在正确的时间收集凳子可能具有挑战性，research shows。

Blood Tests for Bile Acid Malabsorption

Your doctor may also do a blood test to look for an increase in blood markers, including C4 (an enzyme) or FGF-19 (a gut hormone), both of which can rise when a person has BAM. Unfortunately, neither test is considered highly accurate. C4 tests can detect BAM between 71% and 85% of the time; FGF-19 tests between 63% and 72% of the time,found one review。

A SeCHAT Test

该测试涉及吞咽含有合成胆汁酸的胶囊以及放射性示踪剂，然后在七天后进行全身扫描，以确定体内多少物质。

SECHAT测试被认为是诊断BAM的黄金标准，它们的精度率达到93％，调查结果显示。Unfortunately, they’re difficult to access, since the tests are only available in Canada and some parts of Europe, and not in the United States.

Diagnosis by Treatment

The lack of reliable testing options has led many gastroenterologists to look to a simpler, though slightly less-scientific option for determining if a patient has BAM. “It’s easier if we just try to treat the bile acid malabsorption with medication and monitor a patient’s response,” Dr. Hakim says. Dr. Farhadi takes a similar approach. “If we can manage the symptoms with medications, I call the diagnosis. Diagnosis by treatment is the more common approach for doctors in the US,” he says.

Bile Acid Malabsorption Treatment

In some cases, BAM can be treated by addressing the underlying causes. “If you can get Crohn’s or SIBO under control, for instance, the BAM will likely resolve,” says Dr. Hakim. “But someone who has BAM from surgery will have it for the rest of their life.” Other treatment options include medications and diet changes.

Medications for Bile Acid Malabsorption

Doctors typically rely on bile acid sequestrants or binders such as cholestyramine or colestipol to manage BAM. “These binders are sticky materials that bind to bile acids to reduce diarrhea,” explains Dr. Farhadi. Both meds, which come as a powder that can be mixed with liquid to drink, are highly effective at reducing diarrhea caused by BAM.

缺点？结合作用可能会导致便秘或腹胀。粘合剂还可以与您可能要服用的任何其他药物结合，并通过凳子将其送出，使它们无效。法哈迪博士说：“因此，您应该避免在服用胆汁酸粘合剂之前或之后服用其他任何药物。”

That same binding mechanism can also set the stage for potential nutrient deficiencies, especially of fat-soluble vitamins like A, D, E, and K. You and your doctor can keep an eye on your nutrient levels and determine if you need to take a supplement.

BAM的饮食变化

In addition to other treatments, your doctor may also recommend a simple but often effective strategy: sticking with a low-fat diet. Eating more fat stimulates the production of more bile, causing more bile to end up in the colon where it can trigger diarrhea. The reverse is also true: You’ll make less bile, and have less diarrhea, when you limit your fat intake. Whatever approach you and your doctor take, know that bile acid malabsorption is controllable. Keep working with your healthcare team until you find a solution that works for you.

Meet Our Writer

玛丽格雷斯·泰勒（Marygrace Taylor）

玛丽格雷斯·泰勒（Marygrace Taylor）is a health and wellness writer for Parade, SELF, Prevention, and other publications. She lives in Philadelphia with her husband and son. Visit her atmarygracetaylor.com。

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