Understanding Bile Acid Diarrhea

Bile acid diarrhea (BAD) is a condition in which bile acids are not properly processed within the digestive system, resulting in symptoms of chronic diarrhea. This condition can also be known as bile acid malabsorption (BAM). However, 2009 research suggests that the condition may not always be due to malabsorption.

Researchers in this area believe that BAD is not as rare a condition as was once thought. They also believe that BAD is an under-diagnosed condition—one that should be considered for anyone who is experiencing chronic diarrhea of unknown cause—in particular, people who have the symptoms of diarrhea-predominant irritable bowel syndrome (IBS-D) or functional diarrhea. The problem with this under-diagnosis is that it may prevent people from getting proper treatment.

To best understand BAM, it helps to learn how digestion is supposed to work. Bile acids are produced by your liver and stored in your gallbladder. When you eat foods containing fat, these acids are released into the small intestine so the fats can be broken down and absorbed into your body.

Bile acids are then reabsorbed at the level of the small intestine back into the liver for re-release as needed. Typically only a small amount of these acids make their way into the large intestine.

However, when BAD is present, excessive amounts of bile acids are flushed into the large intestine. This leads to increased fluid secretion, resulting in watery stools and a speeding up of intestinal motility—both of which end with symptoms of diarrhea.

The following health problems may contribute to the development of BAD:

• Ileal (small intestine) disease
• Ileal surgery (often as a treatment for Crohn's disease)
• Gallbladder removal (cholecystectomy)
• Small intestinal bacterial overgrowth (SIBO)
• Pancreatic insufficiency
• Radiation for cancer
• Microscopic colitis
• Short bowel syndrome

BAD manifests primarily as the experience of chronic bouts of diarrhea. Some or all of the following symptoms may also be present:

• Watery diarrhea
• Diarrhea with urgency
• Diarrhea in the middle of the night
• Soiling accidents
• Bloating

Doctors characterize bile acid malabsorption by type, depending on its cause:

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

Given the new look at the role of inhibition of the feedback loop for the synthesis of bile acids, the term idiopathic bile acid malabsorption (I-BAM) may go out of favor.

The optimal diagnostic test for the presence of BAD is called the 75-selenium homotaurocholic acid test (SeHCAT) test. 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 percent is considered to be indicative of the presence of BAM.

Unfortunately, the test is not available in the United States. It is believed that this lack of access to the 75SeHCAT test contributes to the under-diagnosis of BAD.

Some physicians turn to a trial of medication for BAD as an alternative to the 75SeHCAT test. If the medication results in an improvement in symptoms, BAD (or BAM) becomes the diagnosis.

One downside of this is that one of the primary medications used for BAD is not well-tolerated. It is often discontinued—particularly when people have not received a definitive diagnosis that might help with medication compliance.

Currently in the United States, a third method requires a ​48-hour stool collection, to analyze bile acids within the colon. It is considered the most direct way to identify patients with BAD.

In cases where BAD is the result of an identifiable disease, treatment will focus on addressing that disease itself. In cases where no underlying cause can be identified, BAD would be treated with a class of medication known as bile acid sequestrants or binders.

Such medications appear to work on the symptoms of BAD by binding to the acids and thereby reducing their effects on the large intestine. These are the current members of this class, the prescription of which for BAD would be considered off-label:

• Cholestyramine (Questran)
• Colesevelam (WelChol)
• Colestipol (Colestid)

These medications are typically effective in eliminating the symptoms of BAD. However, when the medications are prescribed at the dosage for the condition they have FDA approval (e.g. high cholesterol), constipation and other digestive symptoms may be experienced. If you have been prescribed one of these medications, it is important to work with your doctor to find a dosage that is right for you. 

It is important to note that these medications can affect the absorption of other medications you might be taking. Therefore, they should be taken four to six hours before or after any other needed medication.

Although continued research is needed, it would now appear that BAD is more common than was previously thought. If you have been diagnosed with IBS-D or otherwise dealing with symptoms of chronic diarrhea—and your doctor has not yet ruled out BAD—you might want to discuss the issue with them to see if this under-diagnosed health condition is at the root of your symptoms.