Increased colonic bile acid exposure: a relevant factor for symptoms and treatment in IBS

Objective Bile acids may play a role in the pathogenesis of IBS. We investigated the potential effects of bile acids entering the colon and its role in the symptom pattern in IBS. Design We measured 75 Se-labelled homocholic acid-taurine ( 75 SeHCAT) retention, and serum levels of 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor (FGF) 19 in patients with IBS (n=141) and control subjects ( 75 SeHCAT n=29; C4 and FGF19 n=435). In patients with IBS stool frequency and form, as well as GI symptom severity were registered, and in a proportion of patients colonic transit time and rectal sensitivity were measured (n=66). An 8-week open-label treatment with colestipol was offered to patients with 75 SeHCAT <20%, and the effect of treatment was evaluated with IBS severity scoring system and adequate relief of IBS symptoms. Results Compared with controls, patients with IBS had lower 75 SeHCAT values (p=0.005), higher C4c levels (C4 corrected for cholesterol) (p<0.001), but similar FGF19 levels. Abnormal 75 SeHCAT retention (<10%) was seen in 18% of patients, whereas 23% had elevated C4c levels. Patients with IBS with 75 SeHCAT retention <10% had more frequent stools, accelerated colonic transit time, rectal hyposensitivity, a higher body mass index, higher C4c and lower FGF19 levels. Colestipol treatment improved IBS symptoms (IBS severity scoring system 220±109 vs 277±106; p<0.01), and 15/27 patients fulfilled criteria for treatment response (adequate relief ≥50% of weeks 5–8). Conclusions Increased colonic bile acid exposure influences bowel habit and colonic transit time in patients with IBS. A high response rate to open label treatment with colestipol supports this, but placebo-controlled studies are warranted.