Baseline visit Ten subjects with IBS will be recruited from outpatient clinics. Disease severity will be determined at enrolment with a validated IBS symptom questionnaire. Routine blood tests including full blood count, biochemistry profile and C-reactive protein will be obtained. Rectal sensitivity to pressure and pain will be assessed with Barostat device. Barostat device has been used in many other studies as a measure of visceral hypersensitivity. Equipment for both tests is currently in use at our laboratory. A baseline colonoscopy will be performed and rectal biopsies will be taken. Ten controls undergoing screening colonoscopy for polyps or colorectal cancer and subsequently found to have a normal colonoscopy will be included to participate in the FGI-Bx study, in which their tissue samples would be used in this study.