['Patients with collagenous colitis have an impaired mucosal barrier. Moreover, collagenous colitis is associated with bile acid malabsorption. Bile acids can increase bacterial mucosal uptake in humans. Mucosal barrier function was investigated by exposing colonic biopsies to chenodeoxycholic acid (CDCA) or deoxycholic acid (DCA) in Ussing chamber experiments.', 'To find if low levels of bile acids increase bacterial uptake in colonic biopsies from collagenous colitis patients.', 'The study comprised 33 individuals; 25 with collagenous colitis (14 in clinical remission without treatment, 11 with active disease and 10 examined in clinical remission resulting from treatment with 6 mg budesonide); eight healthy individuals undergoing screening colonoscopy served as controls. Endoscopic biopsies from the sigmoid colon were mounted in modified Ussing chambers and assessed for short-circuit current (Isc), potential difference, trans-epithelial resistance and transmucosal passage of Escherichia coli K12 after adding 100 μmol/L CDCA or DCA.', 'When adding 100 μmol/L CDCA or DCA, bacterial uptake increased fourfold in biopsies of patients in remission; CDCA 6.5 units [2.5-9.8] and DCA 6.2 units [2.1-22] (median [IQR]), compared with uptake in biopsies without added bile acids 1.6 units [1.1-3] (P=0.004 and P=0.01 respectively). In active disease and in patients in remission due to budesonide treatment, bile acids did not affect bacterial uptake. Confocal microscopy revealed trans-epithelial passage of E. coli K12 within 30 min.'] Do low levels of bile acids increase bacterial uptake in colonic biopsies from patients with collagenous colitis in remission?