Định nghĩa loét viêm đại tràng (UC) là một tình trạng viêm mãn tính không rõ nguyên nhân ảnh hưởng đến đại tràng cho một mức độ biến proximally từ trực tràng. Các hệ thống khác như da, mắt và khớp có thể bị ảnh hưởng. Khởi phát thường là dần dần trong một số tuần với các triệu chứng chủ yếu là tiêu chảy có máu. | 46 DIARRHOEAL ILLNESSES ULCERATIVE COLITIS I DEFINITION Ulcerative colitis UC is a chronic inflammatory condition of unknown aetiology that affects the colon for a variable extent proximally from the rectum. Other systems such as eyes skin and joints may be affected. The onset is usually gradual over a number of weeks with the major symptom being bloody diarrhoea. EPIDEMIOLOGY The peak age of presentation is in the 20-40 year range with a secondary peak in late middle age although the condition may present at any age. The incidence ranges from 3-15 100 000. It is probable that there is a genetic component to the development of ulcerative colitis. Certain groups such as Caucasians generally and Jewish populations specifically seem more prone to developing the condition. Siblings and family members of those affected also have higher risks of developing the condition with approxi mately a 1 lifetime risk whilst offspring Fig. 1 Inflamed rectal mucosa of uc. of ulcerative colitis sufferers have about a 10 risk of developing the condition. As yet no consistent genetic abnormality has been identified although many candidate genes have been studied. HLA associations have been made particularly with HLA-DR2 but this has not been reliably reproduced. The aetiology remains unknown but various hypotheses have been made including abnormal colonic flora abnormal colonic epithelium and an abnormal host immune response to the colonic flora. Environmental factors also play a part as it is clear that nonsmokers are more prone to developing uc than smokers and those who have been heavy smokers are at particular risk of developing uc especially within 2 years of stopping smoking. NATURAL HISTORY Presentation The symptoms are of increased stool frequency de-creased stool consistency blood in the stool tenesmus and mild abdominal pain. Up to a third of patients at presentation have their entire colon affected and it is usually this group that suffer the most severe symptoms and have .
