Overview
Bile acid malabsorption (BAM) — also called bile acid diarrhoea — occurs when bile acids that should be reabsorbed in the terminal ileum instead spill into the colon, where they stimulate water and electrolyte secretion and accelerate colonic motility, causing chronic watery diarrhoea. BAM is estimated to be responsible for up to 30% of cases labelled as diarrhoea-predominant IBS (IBS-D) and is profoundly under-diagnosed. Primary (type 2) BAM involves idiopathic hepatic overproduction of bile acids. Secondary (type 1 and 3) BAM follows Crohn's disease of the ileum, ileal resection, cholecystectomy, or radiation.
Symptoms
Chronic watery or loose diarrhoea, often with urgency
Postprandial diarrhoea — onset within 1–2 hours after eating, especially after fatty meals
Yellow or greasy stools (steatorrhoea in severe cases)
Abdominal cramping and bloating
Faecal urgency and occasional incontinence, particularly in the morning
Common Causes
Crohn's disease affecting the terminal ileum — impairs active reabsorption of bile acids
Previous ileal resection or bypass surgery — removes the bile acid reabsorption site
Cholecystectomy (gallbladder removal) — disrupts the enterohepatic circulation and bile acid cycling
Radiation therapy to the lower abdomen or pelvis — damages the ileal mucosa
Idiopathic (primary) BAM — hepatic overproduction of bile acids without identifiable cause; the most common and most overlooked type
Self-Care Tips
Follow a low-fat diet (aim for less than 40g total fat per day) — fat triggers gallbladder contraction and bile acid release, worsening symptoms
Eat smaller, more frequent meals to reduce the bile acid bolus delivered to the ileum with each meal
Bile acid sequestrants prescribed by your doctor (cholestyramine, colesevelam, or colestipol) are highly effective and dramatically reduce diarrhoea
Take the sequestrant 30 minutes before meals for maximum effect
Avoid very fatty, fried, or spicy meals which are the most potent symptom triggers
Keep a food diary to identify your personal worst trigger foods, as fat content varies widely between meals
When to See a Doctor
If you have persistent diarrhoea and have a history of Crohn's disease, ileal surgery, or cholecystectomy, ask your gastroenterologist specifically about bile acid malabsorption. Diagnosis is confirmed by a SeHCAT scan (selenium-75 homocholic acid taurine retention test) or a fasting serum 7α-hydroxy-4-cholesten-3-one (C4) level — both are non-invasive.
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