The hypothesis is that ulcerative colitis (UC) is caused by a barrier dysfunction of the colonic mucus layer. The background of the study is the finding, that the phosphatidylcholine (PC) content of the colonic mucus is strongly reduced in UC compared to healthy controls and patients with Crohn´s disease. The content was meuasured in non-inflamed areas of the colon in UC. Thus, we evaluate whether a substitution of colonic PC is an effective method.