消化道病理二PPT.ppt

发病机制（Pathogenesis） 原因不清，可能与遗传相关 The cause of ulcerative colitis is unknown. In some families as many as six patients with this disease have been described, and concordance has been reported in monozygotic twins. However, available family studies do not suggest any distinct mode of genetic transmission. 自身免疫病机制 The possibility that an abnormal immune response may be involved has been studied extensively. There is abundant lymphoid tissue throughout the colon, and ulcerative colitis may occur with autoimmune-like conditions, such as uveitis, erythema nodosum, and vasculitis. Increased circulating antibodies against antigens in colonic epithelial cells and against cross-reacting antigens in enterobacteria may occur. Antineutrophil cytoplasmic antibodies are found in 80% of patients with ulcerative colitis. However, these abnormalities are neither unique for ulcerative colitis, nor are they a prerequisite for the development of the disease. * 病理变化（Pathology） Ulcerative colitis is a diffuse disease. It usually extends from the most distal part of the rectum（远端直肠） for a variable distance proximally (Fig. 13-26). Sparing of the rectum or involvement of the right side of the colon alone is rare and suggests the possibility of another disorder, such as Crohn disease. Inflammation in ulcerative colitis is generally limited to the colon and rectum. It rarely involves the small intestine, stomach, or esophagus. Ulcerative colitis is essentially a mucosal disease. Deeper layers are uncommonly involved, mainly in fulminant cases and usually in association with toxic megacolon. * 三大主要病变 Three major pathologic features characterize ulcerative colitis and help to differentiate it from other inflammatory conditions: Figure 13-26. Ulcerative colitis. Prominent erythema and ulceration of the colon begin in the ascending colon and are most severe in the rectosigmoid area. * The following morphologic sequence may develop rapidly or over a course of years. EARLY COLITIS: Earl