Evolution of clinical behaviour in Crohn's disease: predictive factors of penetrating complications.

BACKGROUND AND AIMS: Crohn's disease is a heterogeneous entity. The Vienna Classification defines three different clinical patterns: 'non-stricturing, non-penetrating', 'stricturing' and 'penetrating'. Aim of this study was to assess the change in clinical behaviour over time and to evaluate whether an evolution towards penetrating complications can be predicted. METHODS: A total of 139 patients with non-penetrating behaviour at the time of diagnosis were included. The mean follow-up was 4.84 years (range 1-23.2 years). The clinical behaviour, according to the Vienna Criteria, was assessed at the diagnosis and at the end of follow up. Statistical analysis was performed by means of the Kaplan-Meier method and standard logistic regression analysis. RESULTS: The cumulative probability of a change in clinical behaviour was 22, 38 and 63% at 3, 6 and 12 years, respectively, and the cumulative probability of developing penetrating complications was 22, 33 and 55% at 3, 6 and 12 years, respectively. Young age at diagnosis (<40 years) and a stricturing behaviour are independent risk factors of developing major penetrating complications (internal fistula, mass or abscess): OR=6.0, 95% CI 1.1-30.5; OR=4.0, 95% CI 1.5-10.9, respectively, but not perianal disease. CONCLUSIONS: The behavioural classification of Crohn's disease is a dynamic model in which each status should be considered as not fixed but evolutive. Perianal disease should be considered a distinct pattern of penetrating behaviour.