The hypothesis is, that ulcerative colitis is caused by a barrier defect of the colonic mucus layer. The background of the study is the finding, that the phosophatidylcholine content of the colonic mucus is strongly reduced in ulcerative colitis (UC) compared to healthy controls and patients with Crohn´s disease. The content was measured in non-inflamed areas of the colon in UC. Thus, we evaluate whether a substitution of colonic PC is an effective method for steroid dependent UC. See: Gut. 2005 Jul;54(7):966-71. Stremmel et al.