AIM:To assess the efficacy of endocytoscopic narrowband imaging(EC-NBI)for evaluating the severity of inflammation in ulcerative colitis(UC).METHODS:This retrospective study was conducted at a single tertiary care referral center.We included UC patients who underwent colonoscopy with endocytoscopy from July 2010 to December 2013.ECNBI was performed,and the images were evaluated by assessing visibility,increased vascularization,and the increased calibers of capillaries and were classified as Obscure,Visible or Dilated.Obscure was indicative of inactive disease,while Visible and Dilated were indicative of acute inflammation.This study received Institutional Review Board approval.The primary outcome measures included the diagnostic ability of EC-NBI to distinguish between active and inactive UC on the basis of histological activity.The conventional endoscopic images were classified according to the Mayo endoscopic score.A score of 0 or 1 indicated inactive disease,whereas a score of 2 indicated active disease.RESULTS:Fifty-two patients were enrolled.There was a strong correlation between the EC-NBI findings and the histological assessment(r=0.871,P<0.01).The sensitivity,specificity,positive predictive value,negative predictive value,and accuracy of EC-NBI for diagnosing acute inflammation were 84.0%,100%,87.1%,100%,and 92.3%,respectively,while those for the Mayo endoscopic score were 100%,40.7%,100%,61.0%,and 69.2%,respectively.Compared with conventional endoscopy,EC-NBI was superior in diagnostic specificity,negative predictive value,and accuracy(P<0.001,P=0.001 and P=0.047,respectively).CONCLUSION:The EC-NBI finding of capillaries in the rectal mucosa was strongly correlated with histological inflammation and aided in the differential diagnosis between active and inactive UC. AIM: To assess the efficacy of endocytoscopic narrowband imaging (EC-NBI) for evaluating the severity of inflammation in ulcerative colitis (UC). METHODS: This retrospective study was conducted at a single tertiary care referral center. We included UC patients who underwent colonoscopy with endocytoscopy from July 2010 to December 2013. ECNBI was performed, and the images were evaluated by assessing visibility, increased vascularization, and the increased calibers of capillaries and were classified as Obscure, Visible or Dilated. Obscure was indicative of inactive disease, while Visible and Dilated were indicative of acute inflammation. This study received Institutional Review Board approval. The primary outcome measures included the diagnostic ability of EC-NBI to distinguish between active and inactive UC on the basis of histological activity. The conventional endoscopic images were classified according to the Mayo endoscopic score. A score of 0 or 1 indicates inactive disease, an a score of 2 ind The sensitivity, specificity, positive predictive value, negative predictive value (r = 0.871, P <0.01) , and accuracy of EC-NBI for diagnosing acute inflammation were 84.0%, 100%, 87.1%, 100%, and 92.3%, respectively, while those for the Mayo endoscopic score were 100%, 40.7%, 100%, 61.0% and 69.2%, respectively. Compared with conventional endoscopy, EC-NBI was superior in diagnostic specificity, negative predictive value, and accuracy (P <0.001, P = 0.001 and P = 0.047, respectively) .CONCLUSION: The EC-NBI finding of capillaries in the rectal mucosa was strongly correlated with histological inflammation and aided in the differential diagnosis between active and inactive UC.