["Anal fistula in Crohn's disease is reportedly intractable, and little is known about factors influencing the outcome of surgery. The purpose of this study was to clarify the current status of surgery for anal fistula in Crohn's disease, and possible factors influencing surgical outcome were investigated.", "From August 1993 to September 1998, 39 of 239 Crohn's disease patients underwent long-term seton drainage. The patients were divided into two groups: patients who received simultaneous bowel and anus operation (simultaneous group; n = 11) and a control group ( n = 28).", 'Twenty-nine of the 39 (74%) patients received two seton drains or more, with a mean of 2.7. Twenty-one (54%) patients received two or more operations. The rate of seton drain removal was 52% at 12 months after operation and 86% at 24 months. The cumulative rate of seton drains remaining at 12 months after the first operation was 10% in the simultaneous group and 37.7% in the control group, with a significant difference ( P = 0.038). Multivariate analysis revealed that simultaneous operation was the only significant factor that influenced the surgical results ( P = 0.0489). Seven of the 21 (33%) patients recurred after total removal of seton drain(s). All the patients who had recurrence belonged to the control group. Continence did not deteriorate after seton drainage. Ten patients (26%) required enterostomy and no patient received proctectomy.'] Is simultaneous anus and bowel operation preferable for anal fistula in Crohn 's disease?