AIM:To determine whether prior appendectomymodifies the phenotype and severity of Crohn’s disease.METHODS:Appendectomy status and smoking habitswere specified by direct interview in 2838 patientsconsecutively seen between 1995 and 2004.Occurrenceof complications and therapeutic needs were reviewedretrospectively.Additionally,annual disease activitywas assessed prospectively between 1995 and 2004 inpatients who had not had ileocecal resection and of amatched control group.RESULTS:Compared to 1770 non-appendectomizedpatients,appendectomized patients more than 5 yearsbefore Crohn’s disease diagnosis(n=716)were moreoften females,smokers,with ileal disease.Cox regressionshowed that prior appendectomy was positively relatedto the risk of intestinal stricture(adjusted hazard ratio,1.24;95% confidence interval,1.13 to 1.36;P=0.02)and inversely related to the risk of perianal fistulization(adjusted hazard ratio,0.75;95% confidence interval,0.68 to 0.83;P=0.002).No difference was observedbetween the two groups regarding the therapeuticneeds,except for an increased risk of surgery inappendectomized patients,attributable to the increasedprevalence of ileal disease.Between 1995 and 2004,Crohn’s disease was active during 50% of years inappendectomized patients(1318 out of 2637 patient-years)and 51% in non-appendectomized patients(1454out of 2841 patient-years;NS).CONCLUSION:Prior appendectomy is associated witha more proximal disease and has an increased risk ofstricture and a lesser risk of anal fistulization.However,the severity of the disease is unaffected. AIM: To determine whether prior appendectomymodifies the phenotype and severity of Crohn’s disease. METHODS: Appendectomy status and smoking habitswere specified by direct interview in 2838 patientsconsecutively seen between 1995 and 2004.Occurrenceof complications and therapeutic needs were were reviewedretrospectively .Additionally, annual disease activitywas assessed prospectively Between 1995 and 2004 inpatients who had had had ileocecal resection and of amatched control group .RESULTS: Compared to 1770 non-appendectomizedpatients, appendectomized patients more than 5 years prior to Crohn’s disease diagnosis (n = 716) were moreoften females, smokers, with ileal disease. Cox regressionshowed that prior appendectomy was positively related to the risk of intestinal stricture (adjusted hazard ratio, 1.24; 95% confidence interval, 1.13 to 1.36; P = 0.02) and inversely related to the risk of perianal fistulization % confidence interval, 0.68 to 0.83; P = 0.002) .No difference was observedbetween the two groups regarding the therapeuticneeds, except for an increased risk of surgery in appendectomized patients, attributable to the increasedprevalence of ileal disease.Between 1995 and 2004, Crohn’s disease was active during 50% of years in appendectomized patients (1318 out of 2637 patient-years) and 51% in non-appendectomized patients (1454 out of 2841 patient-years; NS). CONCLUSION: Prior appendectomy is associated witha more proximal disease and has an increased risk of stricture and a lesser risk of anal fistulization. Host, the severity of the disease is unaffected.