ObjectiveTo investigate the significance of endoscopic punctiform erosion around appendiceal orifice with diffused inflammation in left semicolon in the diagnosis of ulcerative colitis. MethodsTwenty-nine patients with endoscopic punctiform erosion around appendiceal orifice with diffused inflammation in left semicolon treated in West China Hospital from January 2007 to November 2012 were included in our study.Patients with either edema,ulcer,polyps around the appendiceal orifice,inflammation in the ascending colon or transverse colon,or segmental inflammation in left semicolon were excluded.The endoscopic characteristic changes and the final diagnosis were compared by means of the pathological biopsy. ResultsOf the total 29 patients with characteristic changes under the endoscope,26 patients were eventually diagnosed to have left-sided ulcerative colitis,one was identified to be with Cronh's disease,and the remaining two patients could not be classified. ConclusionOur findings suggest that the characteristic changes under the endoscope may help the diagnosis of ulcerative colitis.