High Prevalence of Idiopathic Bile Acid Diarrhea Among Patients With Diarrhea-predominant Irritable Bowel Syndrome Based on Rome III Criteria.

Background & Aims: Some studies have found that patients with idiopathic bile acid diarrhea (BAD) present with symptoms of diarrhea-predominant irritable bowel syndrome (D-IBS). However, these studies were either retrospective, did not define D-IBS according to current criteria, or included patients with chronic functional diarrhea. We performed a prospective study of the prevalence of idiopathic BAD in consecutive patients fulfilling the Rome III criteria for D-IBS. Methods: We analyzed data from 118 consecutive adult patients who fulfilled the Rome III criteria for D-IBS (mean age, 41.7 years; 72.9% female), seen at 2 gastroenterology clinics in the UK. We excluded patients with risk factors for BAD (previous history of cholecystectomy, terminal ileal Crohn's disease, terminal ileal resection or right hemicolectomy, pelvic or abdominal radiotherapy, celiac disease, or microscopic colitis). Participants completed questionnaires at baseline (on demographics, hospital anxiety, somatization, and depression, as well as the patient health questionnaire-12 and the short form-36 [SF-36]), and then received the (75)selenium homocholic acid taurine retention test. Retention of (75)selenium homocholic acid taurine 7 days after administration was used to identify patients with idiopathic BAD (mild BAD, 10%-14.9%; moderate BAD, 5.1%-9.9%; and severe BAD, ≤5%). Results: Twenty-eight were found to have BAD (23.7% of total), with similar percentages at each study site (25.3% and 20%; P=.54). Eight patients had mild BAD (28.6%), 8 had moderate BAD (28.6%), and 12 had severe BAD (42.8%). There was no statistical difference in age or sex, or depression, patient health questionnaire-12, or SF-36 scores, between individuals with vs without BAD. However, patients with BAD had a higher mean body mass index than those without BAD (31.6 vs. 26.4; P=.003). Physical activity (based on the SF-36) was significantly lower in subjects with moderate (43.8) or severe BAD (41.7), compared to patients with mild BAD (87.5) (P=.046). Conclusion: Almost 25% of patients presenting with D-IBS have idiopathic BAD; most cases are moderate to severe. Guidelines should advocate testing to exclude BAD before patients are diagnosed with D-IBS.