For this list, all potentially interesting covariates will be documented by adding coded patient-related data, in order to allow determination of associated risk factors by uni- and multivariate analysis. The following patient-related information will be requested from the HIS: number of participating hospital, date of admission and discharge, age, weight, sex, region of living, length of stay, diagnosis on admission, hospital outcome in terms of mortality, comorbidity details (based on ICD-9 coding), presence of gastro(duodenal) investigations during hospital stay (eg. gastroscopy), discipline of treating clinician and/or hospital ward.