Understanding Diarrhea and Bile Acid Malabsorption: Causes, Symptoms, and Treatment

Diarrhea is a sensitive subject that most people prefer to avoid discussing. However, it remains one of the most frequently encountered medical conditions. Each year in the United States, approximately 3.5 million people seek medical attention due to diarrheal symptoms.
When left untreated, diarrhea can lead to significant health complications. This is primarily because it causes severe fluid loss in the body. Understanding different types of diarrhea, including conditions like bile acid malabsorption (BAM), also known as bile malabsorption, and their appropriate treatments is crucial for preventing such complications.

What causes diarrhea?

Diarrhea manifests as loose, typically watery bowel movements. This condition occurs when harmful substances or disease-causing organisms enter your digestive tract. Your body’s defense mechanism responds by attempting to eliminate these invaders through flushing. Instead of the normal digestive process where liquids combine with fiber and other substances to form solid stools, the result is watery waste that moves rapidly through the system, particularly the colon.

This continuous loss of fluids can lead to dehydration, particularly if you cannot maintain adequate fluid intake to compensate for the loss. Depleting essential electrolytes — including minerals like sodium and potassium — can result in muscle weakness and potentially dangerous heart rhythm disturbances. While frequent bathroom visits are common with diarrhea, the composition of the stool is more significant from a health perspective. Common accompanying symptoms include stomach cramping, nausea, and extreme tiredness.

The duration of symptoms often indicates the underlying cause:

Acute diarrhea persists anywhere from 2 days to 2 weeks, while persistent diarrhea continues for 2 to 4 weeks. Both varieties typically result from infections caused by bacteria, viruses, or parasites. Consuming contaminated food is a frequent source of infectious diarrhea.

Various medications can trigger diarrhea, including antibiotics, nonsteroidal anti-inflammatory medications, antacids, and certain drugs used to treat blood pressure, diabetes, and heart conditions.

Chronic diarrhea extends beyond four weeks and affects roughly 5% of the adult and adolescent population. It can lead to weight reduction and nutritional deficiencies. Chronic diarrhea might indicate serious medical conditions like ulcerative colitis or Crohn’s disease, both typically characterized by blood in stools. It can also signal less severe conditions, such as irritable bowel syndrome (IBS).

A frequently unrecognized cause of chronic diarrhea is bile acid malabsorption (BAM), also known as bile acid diarrhea (BAD). This condition surprisingly accounts for 25% to 50% of chronic diarrhea cases without bloody stools. Many people wonder, “What causes bile acid diarrhea?” and “What does bile acid diarrhea look like?” We’ll explore these questions in detail.

Understanding Bile Acid Malabsorption

Bile acids play a vital role in fat digestion. These substances are produced by the liver, stored in the gallbladder, and released into the small intestine during digestion. Most are typically reabsorbed in the final section of the small intestine, called the ileum, returned to the liver, and recycled through a process known as enterohepatic circulation. However, when this reabsorption process fails, bile acids enter the colon, resulting in urgent, watery diarrhea.

Bile acid malabsorption can also occur when your liver produces excessive bile acid, a condition known as excess bile acid synthesis. Symptoms of excess bile production can include frequent, watery stools and abdominal discomfort. On the other hand, symptoms of low bile production may include difficulty digesting fats and fat-soluble vitamins.

Additionally, conditions like Crohn’s disease, celiac disease, and cholecystectomy (gallbladder removal) can trigger BAM, although in some instances, the underlying cause remains unidentified, leading to what’s termed idiopathic bile acid diarrhea.

What does bile acid diarrhea look like?

Bile acid diarrhea symptoms often include:

1. Frequent, watery stools
2. Urgency to defecate
3. Abdominal pain or cramping
4. Bloating
5. Fatigue (bile acid malabsorption fatigue is common)

In some cases, people may experience “pooping bile” or notice bile in stool, which can appear as a yellowish or greenish liquid. It’s also worth noting that some individuals may experience what feels like “pooping stomach acid,” which can cause a burning sensation.
The characteristics of bile acid malabsorption stool typically include:

• Watery consistency
• Yellow or green color
• Strong, unpleasant odor
• Presence of undigested bile

It’s important to understand what causes acidic poop, as this can be related to bile acid malabsorption or other digestive issues.

Treating diarrhea

While most acute diarrhea cases resolve naturally, severe cases — characterized by 10 or more daily bowel movements or fluid loss exceeding intake capacity — can lead to dangerous dehydration. If left untreated, this condition can become life-threatening. The risk of dehydration is particularly concerning for children, elderly individuals, and those with compromised immune systems.
During a bout of diarrhea, follow these essential guidelines:

• Maintain fluid intake — While water helps replace lost fluids, it lacks crucial salts and electrolytes. Fruit juices can help maintain potassium levels, though some varieties like apple juice may worsen symptoms. Sports beverages such as Gatorade or Powerade provide both potassium and sodium. Broths and soups offer good sodium content. Avoid consuming caffeinated beverages and alcoholic drinks.

• Explore over-the-counter medications — Products like loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol) can help decrease watery bowel movements.

• Modify your diet — Gradually introduce bland, low-fiber foods such as crackers, toast, eggs, rice, and plain chicken. Avoid consuming dairy products, high-fiber foods, and items containing artificial flavorings or seasonings. In cases of bile acid diarrhea, a low-fat diet may be recommended.

Bile Acid Diarrhea Treatment

For those specifically dealing with bile acid malabsorption, treatment often involves the use of bile acid binders. These medications, also known as bile acid sequestrants, work by binding to bile acids in the intestine, preventing them from causing diarrhea. Common bile acid binders include:

1. Cholestyramine
2. Colestipol
3. Colesevelam
   It’s important to note that bile salts side effects can occur, including constipation, bloating, and gas. Your doctor will work with you to find the right dosage to manage your symptoms effectively.

When do you need to see a doctor for diarrhea?

Contact your healthcare provider if you experience any of these conditions:

• Diarrhea persisting for more than two days without improvement
• Excessive thirst, dry mouth or skin, reduced urination, dark urine, severe weakness, dizziness, or lightheadedness
• Intense abdominal pain or rectal pain
• Blood-tinged or black stools
• Fever exceeding 102 F
• Symptoms of bile acid malabsorption, such as urgency, watery diarrhea, and fecal incontinence
• Lack of bile symptoms, which may include pale-colored stools or difficulty digesting fats

Your doctor may prescribe antibiotics or anti-parasitic medication, though antibiotics won’t help viral diarrhea. If an antibiotic is causing your diarrhea, an alternative medication might be prescribed. Some cases may require intravenous fluid administration.
When diarrhea doesn’t respond to self-treatment or medications, an underlying medical condition may be responsible. Your healthcare team might recommend consultation with a specialist for additional evaluation.

Currently, simple blood or stool tests can diagnose bile acid malabsorption. These may include measuring fecal bile acids or blood tests for C4 levels, which indicate bile acid synthesis. In some countries, a SeHCAT test is used to diagnose BAM. Proper identification is crucial since this type of diarrhea can be effectively managed with medications that bind bile acids in the intestine, known as bile acid sequestrants.

Bile acid binders like cholestyramine or colesevelam are commonly used in bile acid malabsorption treatment. These medications work by binding to bile acids in the intestine, preventing them from causing diarrhea. Recent research has also focused on the role of FGF19, a hormone involved in regulating bile acid synthesis. FGF19 may offer new treatment possibilities for bile acid diarrhea in the future, as it helps regulate the production of primary bile acids in the liver and secondary bile acids in the colon.

It’s important to note that bile acid malabsorption can sometimes be mistaken for other conditions like irritable bowel syndrome or microscopic colitis. Therefore, if you’re experiencing chronic diarrhea, it’s crucial to consult with a healthcare professional for proper diagnosis and treatment. They can help determine if your symptoms are related to ileal disease, excess bile acid synthesis, or other digestive issues.

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Source:
Mayo Clinic (February 24, 2025). What to do about diarrhea. https://mcpress.mayoclinic.org/living-well/what-to-do-about-diarrhea/. Accessed May 30, 2025