AIM To evaluate the potential association between mild duodenal damage and microscopic colitis(MC).METHODS We retrospectively included 105 consecutive patients with type I Marsh-Oberhuber duodenal damage and negativity for immunoglobulin A anti-endomysium and anti-tissue transglutaminase.The following parameters were analyzed:Sex,age at execution of esophagogastroduodenoscopy,duodenal damage,and number of intraepithelial lymphocytes at biopsies,prevalenceof Helicobacter pylori infection,age at execution of colonoscopy,macroscopic and microscopic features of colonoscopy,family history of gastrointestinal and autoimmune diseases,smoking habits,biochemical parameters of inflammation and autoimmunity,use of proton pump inhibitors or nonsteroidal anti-inflammatory drugs,adverse reactions to drugs or foods,pathologies known to be associated with celiac disease or MC,living on a gluten-free diet or on a gluten-low diet for at least 1 mo.RESULTS Colonoscopy was performed in 59 patients,but only in 48 of them biopsies were taken in the entire colon.Considering the latter cohort,the diagnosis of MC was met in 25(52.1%) patients while in 18 patients other pathologic findings were reported:13(27%) cases of nonspecific inflammatory bowel disease,2(4.2%) cases of Crohn’s disease,2(4.2%) cases of eosinophilic gastroenteritis,and 1(2.1%) case of autoimmune enteritis.Five(10.4%) patients had a normal colonoscopic result.Matching the groups by age,and considering only patients who underwent colonoscopy(42.7 ± 15.5 years) vs those who did not undergo colonoscopy(36.9 ± 10.6 years),a statistical difference was found(P = 0.039).Focusing on symptoms,diarrhea was statistically more prevalent in MC group than in patients who did not undergo colonoscopy(P = 0.03).CONCLUSION Mild duodenal damage is associated with MC in more than half of the cases.This association supports the hypothesis of a link between these two entities. AIM To evaluate the potential association between mild duodenal damage and microscopic colitis (MC). METHODS We retrospectively included 105 consecutive patients with type I Marsh-Oberhuber duodenal damage and negativity for immunoglobulin A anti-endomysium and anti-tissue transglutaminase. The following parameters were analyzed: Sex, age at execution of esophagogastroduodenoscopy, duodenal damage, and number of intraepithelial lymphocytes at biopsies, prevalence of Helicobacter pylori infection, age at execution of colonoscopy, macroscopic and microscopic features of colonoscopy, family history of gastrointestinal and autoimmune diseases, smoking habits, biochemical parameters of inflammation and autoimmunity, use of proton pump inhibitors or nonsteroidal anti-inflammatory drugs, adverse reactions to drugs or foods, pathologies known to be associated with Celiac disease or MC, living on a gluten-free diet or on a gluten-low diet for at least 1 mo .RESULTS Colonoscopy was performed in 59 patients, but onl Of 48 biopsies were taken in the entire colon. Patients of the latter cohort, the diagnosis of MC was met in 25 (52.1%) patients while in 18 patients other pathologic findings were reported: 13 (27%) cases of nonspecific inflammatory 2 (4.2%) cases of eosinophilic gastroenteritis, and 1 (2.1%) cases of autoimmune enteritis. Five (10.4%) patients had a normal colonoscopic result. Matching the groups by age, and considering only patients who underwent colonoscopy (42.7 ± 15.5 years) vs those who did not undergo colonoscopy (36.9 ± 10.6 years), a statistical difference was found (P = 0.039) .Focusing on symptoms, diarrhea was statistically more prevalent in MC group than in patients who did not undergo colonoscopy (P = 0.03) .CONCLUSION Mild duodenal damage is associated with MC in more than half of the cases. This association supports the hypothesis of a link between these two entities.