["The aim of this study was describe the frequency and characteristics of perianal surgical intervention (PSI) for Crohn's disease in a population-based cohort of patients with inflammatory bowel disease (IBD).", 'A total of 1421 patients with IBD were recruited, representing approximately 91 per cent of people with IBD in Canterbury, New Zealand. The clinical notes were screened to confirm the diagnosis and extract clinical data, including details of PSIs.', "Some 649 patients with Crohn's disease were included in the analysis, of whom 119 (18.3 per cent) had at least one PSI. Of these, 61 (51.3 per cent) required further procedures. Operations for perianal abscess and fistula accounted for 72.4 per cent of interventions. PSI rates did not differ between the sexes (P = 0.218). Age less than 17 years (adjusted odds ratio (OR) 1.89 (95 per cent confidence interval 1.08 to 3.28)) and ileal disease (OR 1.76 (1.06 to 2.92)) were identified as predictors of PSI. As disease duration increased, so did the proportion of patients with complicated intestinal disease among those who had undergone PSI. The median time to first PSI from diagnosis of Crohn's disease was 28 (interquartile range 7-82) months. Sex, age at diagnosis and disease location did not influence the time to first PSI."] Is ileal disease associated with surgery for perianal disease in a population-based Crohn 's disease cohort?