Can IBD Cause Bile Acid Diarrhea?
Yes, IBD can directly cause bile acid diarrhea (BAD), particularly in Crohn's disease patients with ileal involvement or those who have undergone ileal resection. 1, 2
Mechanisms in IBD
Crohn's Disease with Ileal Disease
- Ileal inflammation or resection disrupts the enterohepatic circulation of bile acids by damaging or removing the terminal ileum, where the apical sodium-dependent bile acid transporter (ASBT) normally reabsorbs conjugated bile acids 3
- Inflammatory cytokines directly suppress ASBT expression at the promoter level, reducing bile acid reabsorption even before structural damage occurs 3
- The inflamed ileum interrupts normal bile acid recirculation, allowing excess bile acids to reach the colon where they stimulate water and electrolyte secretion and accelerate colonic transit 2, 3
Ulcerative Colitis
- The role of BAD in UC is less clear, with lower reported prevalence compared to Crohn's disease 1
- UC patients may still develop BAD through mechanisms that remain incompletely understood 1
Clinical Prevalence
- BAD occurs commonly in CD patients with ileal disease or ileal resection, with a response rate of 73% to bile acid sequestrants reported in one cohort of 39 CD patients who had undergone ileal resection 1
- The severity of bile acid malabsorption shows modest correlation with the length of ileal resection in CD patients 1
- Among patients presenting with chronic diarrhea who have D-IBS type symptoms, 33.6% with positive SeHCAT testing also had terminal ileal Crohn's disease as a predictive factor 4
Diagnostic Approach in IBD Patients
When to Suspect BAD
- Consider BAD in any IBD patient with persistent watery diarrhea despite apparent control of inflammation 1
- Terminal ileal Crohn's disease, terminal ileal resection, and previous cholecystectomy are significant predictive factors for BAD 4
- Symptoms typically include chronic watery diarrhea that worsens after meals, with potential nocturnal diarrhea and fecal incontinence 5
Testing Options
- The AGA suggests testing for bile acid diarrhea in patients presenting with chronic diarrhea (conditional recommendation, low-quality evidence) 1
- SeHCAT scan is the gold standard (retention <15% suggests BAD, <10% is more definitive), though it is not available in North America 1, 5, 4
- In the United States, available tests include 48-hour fecal bile acid measurement and serum fibroblast growth factor 19 (FGF-19), though these require further clinical validation 1
- Given limited test availability, an empiric trial of bile acid sequestrants is reasonable when BAD is suspected, with clinical response suggesting excess bile acids as the cause 1
Treatment Considerations
First-Line Therapy
- Bile acid sequestrants (cholestyramine, colestipol, or colesevelam) are first-line treatment for BAD in IBD patients 1, 5, 2
- Cholestyramine demonstrates a 73% response rate in CD patients with ileal resection 1
- Dose-response relationship exists, with 96% response in patients with <5% SeHCAT retention 5
Important Caveats
- In severe bile acid malabsorption, cholestyramine may paradoxically worsen steatorrhea by further reducing available bile acids needed for fat absorption 1
- If mild BAD is present, bile acid sequestrants effectively control osmotic diarrhea 1
- Multiple pathophysiologic mechanisms may coexist in IBD patients (SIBO, pancreatic exocrine insufficiency, carbohydrate malabsorption), requiring comprehensive evaluation 1
Clinical Pitfalls to Avoid
- Do not assume all diarrhea in IBD is from active inflammation—BAD is a distinct, treatable entity that persists even with mucosal healing 1
- Screen for BAD before attributing persistent symptoms to functional overlay or IBS in IBD patients 1
- Remember that fecal elastase may be falsely low in the setting of diarrhea from any cause, potentially leading to misdiagnosis of pancreatic insufficiency when BAD is the actual culprit 1
- Consider that BAD and fat malabsorption can coexist, particularly in patients with extensive ileal disease or resection 5