Bile acid malabsorption (BAM)
By Dr. Bahir Hadi — Consultant Surgeon, PhD
Bile acid malabsorption (BAM): the overlooked cause of chronic diarrhoea
Bile acid malabsorption (BAM) is a common but heavily under-diagnosed cause of chronic diarrhoea. It is present in up to 30 % of patients otherwise labelled with diarrhoea-predominant irritable bowel syndrome (IBS-D) [1]. BAM occurs when bile acids from the gallbladder are not properly reabsorbed in the distal ileum and instead enter the colon, where they stimulate water and electrolyte secretion → watery diarrhoea.
Three types
| Type | Cause | Share |
|---|---|---|
| Type 1 | Ileal disease: Crohn's, ileal resection, radiation | ~30 % |
| Type 2 | Primary - defective FGF19 feedback | ~50 % |
| Type 3 | Secondary: cholecystectomy, SIBO, coeliac, chronic pancreatitis | ~20 % |
Symptoms
- Watery, yellow-green diarrhoea - often 5-10 times daily
- Urgent need to defecate and fear of incontinence
- Nocturnal diarrhoea - atypical for IBS, suspicious for BAM or IBD
- Cramps, bloating, flatulence
- Weight loss and fat-soluble vitamin deficiencies in severe disease
- Often worse after fatty meals
Key clinical pointer: Up to 50 % of patients after cholecystectomy develop chronic diarrhoea - a large proportion have BAM.
Diagnosis
- SeHCAT scan - gold standard. Measures retention of a radiolabelled bile acid analogue after 7 days. <15 % retention = BAM, <5 % = severe BAM [2].
- Serum C4 (7α-hydroxy-4-cholesten-3-one) - indirect marker of bile acid synthesis; raised in BAM.
- Faecal bile acids (48-hour collection) - alternative if SeHCAT unavailable.
- Empirical treatment trial with bile acid binders - both diagnostic and therapeutic in patients with high clinical suspicion.
Treatment
Bile acid binders (first-line):
- Cholestyramine 4-16 g daily - cheap, but unpleasant taste and drug interactions.
- Colesevelam 1,875-3,750 mg daily - better tolerated.
- Colestipol - alternative.
Take at least 4 hours apart from other medication (also binds vitamins, levothyroxine, warfarin).
Dietary advice:
- Reduce fat to <40 g/day in acute phase
- Avoid alcohol
- Supplement fat-soluble vitamins (A, D, E, K) in severe disease
Treat underlying cause (type 1 and 3) - IBD control, SIBO eradication, coeliac diet.
Why is it missed?
- SeHCAT is not universally available
- Symptoms mimic IBS-D
- Many patients are diagnosed only after 5+ years
- Empirical treatment trials are often skipped in primary care [3]
Treatment at Kirurgen.dk
We investigate chronic diarrhoea with colonoscopy, gastroscopy, coeliac screening and faecal calprotectin - and refer for SeHCAT when BAM is suspected. See also: Chronic diarrhoea, IBS, SIBO, Microscopic colitis.
References
- Wedlake L, A'Hern R, Russell D, et al. Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome. Aliment Pharmacol Ther 2009;30(7):707-17.
- Vijayvargiya P, Camilleri M, Shin A, Saenger A. Methods for diagnosis of bile acid malabsorption in clinical practice. Clin Gastroenterol Hepatol 2013;11(10):1232-9.
- BSG guidelines on the management of functional bowel disorders. Gut 2021;70:1214-40.
More on this topic at Kirurgen.dk
Category: Gastrointestinal