Abstract: Objective To investigate the clinical outcomes of complex perianal fistulas treated with mucosal advancement flap (MF) combined with fistulectomy (FT).Methods A total of 408 patients with complex anal fistula who underwent surgery from January 2012 to January 2022 were selected.According to the surgical methods, they were divided into the observation group (214 cases treated with MF combined with FT) and the control group (194 cases treated with FT combined with seton therapy).Gender, age, location type of fistula, recurrence rate of anal fistula and postoperative anal sphincter function of the two groups were compared through case review and outpatient follow-up.Results At 12, 24, and 48 months after surgery, fistula recurrence rate were 8.2%, 18.2%, and 21.0% in observation group, respectively, compared to 25.5%, 41.9%, and 48.0% in control group (P＜0.05).The curative rate was 80.9% in the observation group and 49.0% in the control group at 24 months postoperatively (P＜0.05).Additionally, 8.2% of patients in the observation group experienced defecation dysfunction compared to 36.7% in the control group postoperatively (P＜0.05).There was no statistically significant difference in wound healing time between the two groups (P>0.05).There was no statistically significant difference in the fecal incontinence severity index(FISI) between the two groups before the operation (P>0.05).One month after surgery, FISI score of treatment group was significantly lower than that of control group (P<0.05).In particular, two months after surgery, FISI of the treatment group was significantly lower than that of the control group (P<0.05).Conclusion The combination of mucosal advancement flap with fistulectomy possesses higher curative rate and lower recurrence and defecation dysfunction rate compared to fistulectomy alone in treating complex anal fistulas.

Key words: fistula; mucosal advancement flap; fistulectomy