The Evolution of Crohnʼs Disease (CD) Behavior in a Population-Based Cohort

Abstract

Purpose: We sought to estimate in a population-based cohort of CD the cumulative probability of developing penetrating or stricturing disease and, among those without a complication at baseline, to assess factors associated with subsequent development of stricturing or penetrating disease. Methods: The medical records of all Olmsted County, Minnesota residents with a diagnosis of CD from 1970 to 2004 were abstracted for information on behavior and location of disease based on the Montreal classification [A1 (age ≤ 16 yr); A2 (age 17 − 40 yr); A3 (age > 40 yr); L1 (terminal ileum); L2 (colon); L3 (ileocolon); L4 (upper gastrointestinal tract); B1 (non-stricturing, non-penetrating); B2 (stricturing) and B3 (penetrating)]. We estimated the cumulative probability of developing B2 or B3 from time of diagnosis using the Kaplan Meier method. In the subset with B1 disease at diagnosis, Cox proportional hazards regression was used to assess the association of B2 or B3 behavior with putative risk factors (age, gender, baseline disease location, smoking history, perianal disease, family history, extra-intestinal manifestations and baseline medications). Results: In our cohort of 306 CD patients, clinical characteristics were: A1, 11.4%; A2, 56.2%, A3, 32.4%; L1, 45.1%; L2, 32.0%; L3, 18.6%; L4, 0.3%; L1 + L4, 2.3%; L2 + L4, 0.3%; L3 + L4 1.3%; B1, 81.4%; B2, 4.6% and B3, 14.0%. The cumulative risk of either B2 or B3 was 11.8% at day 0, 18.6% at 90 days, 22% at 1 year, 33.7% at 5 years, 38.7% at 10 years, 50.8% at 20 years, and 54.4% at 30 years after diagnosis. Among 249 patients with B1 disease at diagnosis, a change in behavior occurred in 66 patients. At 1, 5, 10, 20 and 30 years, the cumulative probabilities of patients with B1 developing either B2 or B3 were 4.1%, 18.5, 24.7, 39.5 and 43.9%; developing B2 were 2.5%, 8.0, 11.0, 17.6% and 17.6%; and developing B3 were 1.7%, 11.4, 15.4, 26.6 and 31.9%, respectively. Change in behavior (either B2 or B3) led to resective bowel surgery within 6 months of the event in 47 patients. Risk factor associated with change in behavior are shown in Table 1.Table: Analysis of Factors Associated with Change in Behavior.Conclusion: In this population-based cohort of CD, almost 19% of patients had already experienced a penetrating or stricturing complications within the first 90 days of diagnosis, and fully half of all patients had experienced a complication by year 20. Factors associated with progression to penetrating or stricturing events were the presence of ileal involvement and perianal disease (borderline significance).