To set up a cohort of at least 400 IBS patients in order to identify different patient subgroups according to phenotypical and genotypical patterns and

To set up a biobank for future translational studies on the pathophysiology of IBS, in order to identify genetic factors to unravel the pathogenesis of IBS and to provide novel therapeutic targets.

Aim of the present study is to set up a large cohort of IBS patients in order to identify different disease characteristics as well as aetiological and pathophysiological factors in (sub)groups of patients with this heterogeneous disorder. Various phenotypical and genotypical markers will be evaluated. For this purpose, blood and faecal samples as well as symptom questionnaires will be collected and visceral perception and intestinal permeability will be measured. In order to increase the sensitivity of the barostat procedure, a pilot study will be performed by measuring patients and healthy controls under meal stimulated and fasting conditions. We aim to set up a biobank for studies on the pathophysiology of IBS, in order to identify genetic factors that may help unravel the pathogenesis of IBS and provide novel therapeutic targets. Consent will be asked to collect data from questionnaires, to store serum samples, DNA, stool and, when endoscopy is performed for clinical reasons, also biopsy specimens.

Inclusion Criteria:

• IBS-patients

Exclusion Criteria:

• Severe co-morbidity hindering a rectal barostat procedure, according to the gastroenterologist's perception.
• Abdominal surgery, except for uncomplicated appendectomy, laparoscopic cholecystectomy or hysterectomy.
• Inability to stop medication that can influence gastrointestinal motility or perception (like loperamide, butylscopolamine, psylliumsead (metamucil), duspatal, metoclopramide, domperidon, erytromycin and serotonin reuptake inhibitors), for at least 3 days before tests.

At least 400 patients with (suspected) IBS referred to the GI-outpatient clinic of the Maastricht University Medical Center will be asked to participate in the study.