Behaviour of Crohn's disease according to the Vienna classification: changing pattern over the course of the disease

Background-Crohn's disease is a heterogeneous disorder with both a genetic and environmental aetiology. Clinical classifications of the disease, such as the newly proposed Vienna classification, may help to define subgroups o f patients suitable for studying the influence of specific genetic or envir onmental factors. Aim-To assess the stability over the course of the disease of its location and behaviour, as determined according to the Vienna classification. Patients and methods-The notes of 297 Crohn's disease patients regularly fo llowed up at our institution were carefully reviewed retrospectively. The b ehaviour and location of the disease according to the Vienna classification were determined at diagnosis and after 1, 3, 5, 10, 15, 20, and 25 years o f follow up. The proportions of the different behaviours and locations of t he disease were calculated at these time points. A statistical analysis of the evolution of these characteristics over 10 years was performed on a sub group of 125 patients with at least 10 years of follow up. The influence of age at diagnosis on location and behaviour of the disease was assessed as well as the influence of location on the behaviour of the disease. Results-The location of the disease remained relatively stable over the cou rse of the disease. Although the proportion of patients who had a change in disease location became statistically significant after five years (p=0.01 ), over 10 years only 15.9% of patients had a change in location (p <0.001) . We observed a more rapid and prominent change in disease behaviour, which was already statistically significant after one year (p=0.04). Over 10 yea rs, 45.9% of patients had a change in disease behaviour (p <0.0001). The mo st prominent change was from non-stricturing non-penetrating disease to eit her stricturing (27.1%; p <0.0001) or penetrating (29.4%; p <0.0001) diseas e. Age at diagnosis had no influence on either location or behaviour of dis ease. Ileal Crohn's disease was more often stricturing, and colonic or ileo colonic Crohn's disease was more often penetrating: this was already the ca se at diagnosis and became more prominent after 10 years (p <0.05). Conclusions-Location of Crohn's disease, as defined by the Vienna classific ation, is a relatively stable phenotype which seems suitable for phenotype- genotype analyses. Behaviour of Crohn's disease according to the Vienna cla ssification varies dramatically over the course of the disease and cannot b e used in phenotype-genotype analyses. The potential influence of genes on the behaviour of Crohn's disease should be studied in subgroups of patients defined by their disease behaviour after a fixed duration of disease.