Factors related to frequency,type, and outcome of anal fistulas in Crohn's disease

PURPOSE: Relation of clinical factors to frequency, type, and, in particular, outcome of anal fistulas in Crohn's disease was studied. METHODS: One hundred twelve patients seen in this hospital between January 1972 and June 1993 who suffered from Crohn's disease were included in the study. Those 35 (31 percent) with anal fistulas were reexamined or interviewed and asked about their perianal symptoms and anal control. RESULTS: Rectal involvement of Crohn's disease was associated with an increased incidence of anal fistula (49vs.17 percent;P<0.01), especially high ones (82vs.17 percent;P<0.01). Ten of 18 patients with low fistulas underwent fistulotomy; all 10 fistulas healed, but slowly (mean healing time, 7.5 months), and 4 of them recurred. Of eight low fistulas managed by drainage alone, four healed. Finally, 11 of 18 patients with low fistulas had their fistulas healed. Fourteen of 17 patients with high fistulas were primarily treated by drainage and 3 by local surgery. Finally, only three patients had healed fistulas—two after simple drainage and one after local surgery, and seven patients had to undergo proctectomy. Only two patients with low fistulas required proctectomy. Eight patients (33 percent) of those 24 with fistulas in whom anal continence could be assessed, 5 with local surgery and 3 with drainage alone, reported minor defects in anal control. CONCLUSIONS: Fistulotomy is a justifiable option with satisfactory results for low symptomatic anal fistulas associated with Crohn's disease, although healing may be delayed and some fistulas will recur. Outcome of high fistulas is less satisfactory, and proctectomy is ultimately required in a number of patients; therefore, for high fistulas a conservative approach is primarily recommended.