High prevalence of primary bile acid diarrhoea in patients with functional diarrhoea and irritable bowel syndrome-diarrhoea, based on Rome III and Rome IV criteria

Background: A high prevalence of primary bile acid diarrhoea (BAD) has been reported for Rome III defined irritable bowel syndrome (IBS)-diarrhoea and functional diarrhoea. We determined whether this still applies under the contemporaneous Rome IV criteria, given that the latter characterises IBS-diarrhoea as having more frequent abdominal pain compared with previous iterations, whilst no longer recognising abdominal discomfort. Methods: Patients referred for a 75SeHCAT test completed a baseline questionnaire comprising, i) demographic data, ii) risk factors for BAD (inflammatory bowel disease, bowel resection, cholecystectomy, microscopic colitis, celiac disease, abdominal-pelvic radiotherapy), iii) the Rome III and IV bowel disorder questionnaire, and iv) mood and somatisation scores. A diagnosis of BAD constituted a 75SeHCAT of ≤15%, with moderate to severe disease being defined as ≤10% and ≤5%, respectively. Findings: Of 300 patients with complete dataset, 184 had no risk factors for BAD and fulfilled criteria for either IBS-diarrhoea or functional diarrhoea. The prevalence of primary BAD was 38% (n = 70/184), with almost half having moderate (n = 16) to severe (n = 17) disease. Using the Rome III criteria, the prevalence of primary BAD was 36% in IBS-diarrhoea (n = 63/173) and 64% (n = 7/11) in functional diarrhoea; p = 0.11. Using the Rome IV criteria, the prevalence of primary BAD was 38% (n = 53/139) in IBS-diarrhoea and 38% (n = 17/45) in functional diarrhoea; p = 0.97. Patients with primary BAD experienced more frequent loose stools (p = 0.01) and had a higher body mass index (p