Bile Acid Diarrhea (BAD) frequently causes a severe burning sensation. BAD occurs when an excessive amount of bile acids enters the large intestine. This excess irritates the sensitive lining of the colon and rectum, causing inflammation and discomfort often described as a severe burn. Treatment focuses on addressing the underlying cause of the bile acid excess while managing this distinct and painful symptom.
The Mechanism of Colonic Irritation
The burning sensation results directly from the chemical properties of bile acids acting upon the colonic mucosa. Bile acids function as detergents to emulsify fats in the small intestine, but they are highly corrosive when reaching the large intestine in high concentrations. These compounds disrupt the colon’s protective epithelial barrier, which is not designed to withstand such detergent activity. This disruption allows irritating substances to penetrate sensitive tissue layers.
The gut microbiota converts primary bile acids into more toxic secondary bile acids, such as deoxycholic acid. These secondary bile acids stimulate the colonic tissue to secrete water and electrolytes, causing characteristic watery diarrhea. Bile acids also trigger the release of inflammatory mediators, which contribute to the feeling of inflammation and intense burning.
Other Indicators of Bile Acid Diarrhea
Beyond the distinctive burning, Bile Acid Diarrhea presents with symptoms related to rapid, liquid bowel movements. The hallmark is chronic, watery diarrhea, often explosive in nature, accompanied by significant urgency. Increased bowel frequency is common, with individuals experiencing multiple movements daily, sometimes waking them from sleep. The stool may appear mushy, unformed, or sometimes pale, yellow, green, or orange due to unabsorbed bile. Other digestive symptoms include:
- Abdominal pain
- Cramping
- Bloating
- Excessive gas
Why Excess Bile Acids Reach the Colon
The digestive system normally recycles bile acids efficiently through the enterohepatic circulation. Bile acids are produced in the liver, stored in the gallbladder, and released into the small intestine for fat digestion. Approximately 95% of these bile acids are reabsorbed in the terminal ileum and returned to the liver for reuse.
BAD occurs when this recycling process is interrupted, allowing excess bile acids to spill into the colon. This interruption is categorized into three types. Type 1 results from ileal disease or damage, such as surgical removal of the terminal ileum or inflammation from Crohn’s disease.
Type 3 is secondary to other gastrointestinal disorders, including Celiac disease, chronic pancreatitis, or cholecystectomy. The most common form is Type 2, or primary BAD, which has no obvious underlying cause. This type is believed to stem from the liver overproducing bile acids due to a breakdown in the feedback loop that signals the liver to slow production.
Diagnosis and Symptom Management
Diagnosis of Bile Acid Diarrhea begins with a review of symptoms and medical history. The SeHCAT scan, which tracks a synthetic radiolabeled bile acid, is often considered the gold standard diagnostic test. Less invasive options include blood tests that measure markers of bile acid synthesis, such as 7-alpha-hydroxy-4-cholesten-3-one (C4).
The primary treatment uses Bile Acid Sequestrants (BAS), such as cholestyramine or colesevelam. These medications bind to excess bile acids in the intestine, forming an insoluble complex. This binding prevents the bile acids from irritating the colon lining, reducing watery diarrhea and the associated burning.
For painful local symptoms, relief involves careful hygiene and barrier protection. Patients should avoid harsh wiping, using gentle cleansing with water or unscented wipes, followed by a soft pat-dry. Applying a protective barrier cream containing zinc oxide or petroleum jelly after each bowel movement creates a physical shield between the sensitive perianal skin and the irritating stool, allowing the tissue time to heal.