Perianal fistulizing lesions of Crohn's disease are associated with long-term behavior and its transition: a Chinese cohort study.

Background/aims: Crohn's disease (CD) has a progressive nature and commonly perianal involvement. The aim of this study is to assess the prevalence, surgical treatment, and outcome of perianal fistulizing CD with associated risk factors in a large Chinese cohort.

Methods: Hospitalized patients diagnosed with CD in our center were consecutively enrolled between January 2000 and December 2018. Transition of disease behavior was classified according to the presence or absence of penetrating behavior (B3 in the Montreal classification) at diagnosis and at a median follow-up of 102 months.

Results: A total of 504 patients were included, of whom 207 (41.1%) were classified as B3 and 348 (69.0%) as L2/3 at follow-up. Transition of behavior to B3 was observed in 86 patients (17.1%). The incidence of perianal fistulizing lesions was 10.9% at 10 years with a final prevalence of 27.0% (n = 136) at the end of follow-up. Multivariate Cox regression identified independent risks of perianal fistulizing lesions for persistent B3 (hazard ratio, 4.72; 95% confidence interval, 1.91-11.66) and behavior transition of progressed to B3 (hazard ratio, 9.90; 95% confidence interval, 4.60-21.33). Perianal surgical treatments were performed in 104 patients (20.6%). Thirty-six cases (7.1%) were refractory, and it is independently associated with behavior of persistent B3 (P= 0.011).

Conclusions: Perianal fistulizing lesions occurred frequently in Chinese CD patients. Its incidence and refractory outcome were closely associated with the penetrating CD behavior. An additional risk of perianal fistulizing lesions was indicated for CD patients with behavior of progressing to B3, suggesting further attention.