[Etiology and pathogenesis of Crohn disease and ulcerative colitis].

The aetiology and pathogenesis of Crohn's disease and ulcerative colitis have not yet been clarified. None of the many investigations on the involvement of genetic, microbial, psychological, immunological and environmental factors have been able to identify a single aetiological agent. Nevertheless, all of these factors could play a role in a multifactorial model of the aetiology and pathogenesis of inflammatory bowel disease.