Abstract: Objective To evaluate the efficacy of transanal opening of intersphincteric space(TROPIS) for the treatment of complex anal fistula. Methods 41 patients with complex anal fistula were randomly divided into two groups by random envelope method:21 patients in the treatment group were treated with TROPIS;20 patients in the control group were treated with traditional low incision and high thread drawing surgery.The curative effect,postoperative pain score,wound healing time,treatment failure rate,anal sphincter function and postoperative complications were compared between the two groups.Results The visual analoguescale scores (VAS) of anal pain in the treatment group and the control group 8 hours,24 hours,3 days,7 days and the first defecation after operation were (1.81±1.12) vs.(5.00±1.49),(1.10±1.14) vs.(4.35±1.42),(0.86±1.01) vs.(4.35±1.27),(0.81±1.08) vs (4.25±1.41),(3.05±1.56) vs (6.70±1.17),respectively,with significant differences (P＜0.01).The VAS of anal pain in the treatment group and the control group 14 days after operation were (0.67±1.07) vs (0.80±1.11),respectively,with no significant difference (P＞0.05).1 case in the treatment group (4.76%) and 1 case in the control group (5.00%) had wound infection after surgery,there was no significant difference in the rate of wound infection between the two groups (P＞0.05).2 cases (9.52%) in the treatment group and 3 cases (15.00%) in the control group underwent postoperative catheterization,there was no significant difference in urinary retention between the two groups (P＞0.05).In the treatment group,16 cases were cured,3 cases were markedly effective,and the total effective rate was 90.48%,while in the control group,16 cases were cured,2 cases were markedly effective,and the total effective rate was 90.00%,there was no significant difference between the two groups (P＞0.05).The wound healing time of the treatment group and the control group were (37.31±3.42) days vs (48.13±4.08) days,respectively,with a statistically significant difference (P＜0.01).12 months after operation,2 patients in the treatment group and 1 patient in the control group lost the follow-up.12 months after operation,the ST Marks anal incontinence scores in the treatment group and the control group were (0.53±1.07) and (1.74±2.77),respectively,with a statistically significant difference (P＜0.05).There were 6 patients (31.58%) in the treatment group and 4 patients (21.05%) in the control group who failed in treatment,there was no significant difference in the rate of treatment failure between the two groups (P＞0.05).Conclusion The TROPIS is reliable in treating anal fistula,and has the advantages of less pain,quick recovery and less damage to anal function.

Key words: anal fistula, preserve the external sphincter, transanal opening of intersphincteric space