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 (75)SeHCAT 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 (75)SeHCAT 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<0.0001) compared to those without BAD, but otherwise no significant differences were seen in age, gender, mood, somatisation, or abdominal pain. The presence of primary BAD in patients classified as overweight or obese was approximately 40% and 60%, respectively. INTERPRETATION: Over a third of patients with Rome IV IBS-diarrhoea or functional diarrhoea have primary BAD, similar to Rome III. We therefore recommend that, in secondary care settings, generic testing for primary BAD should be considered in patients presenting with chronic diarrhoea of presumed functional origin regardless of concomitant abdominal pain. Centres that lack tests for primary BAD, and who empirically treat instead, may consider targeting patients who are overweight or obese.