To evaluate the clinical efficacy of lateral mucosal advancement flap (LMAF) surgery versus ligation of inter-sphincteric fistula tract (LIFT) in the treatment of complex anal fistulas and provide evidence for clinical decision-making.

In this retrospective cohort, propensity score matching was used to balance baseline characteristics. Patients were divided into LMAF group (n=42) and LIFT group (n=48). Clinical cure rate, anal function (Wexner score), complications, and recurrence were analyzed, with subgroup analyses based on fistula number and Parks classification.

The clinical cure rate was 83.3% in the LMAF group and 72.9% in the LIFT group, with no statistically significant difference (χ²=1.413, P=0.235). Anal continence function, assessed using the Wexner incontinence score at 3 (t=0.748, P=0.458) and 6 months (t=1.906, P=0.059) postoperatively, showed no significant differences between the groups. At 12-month follow-up, the recurrence rate in the LMAF group (4.8%) was lower than that in the LIFT group (16.7%), though the difference did not reach statistical significance (χ²=3.245, P=0.072). The postoperative complication rate was significantly lower in the LMAF group (14.3%) compared to the LIFT group (33.3%) (χ²=4.295, P=0.034). Subgroup analysis by the number of fistula tracts demonstrated that there was no statistically significant difference in the incidence of complications and recurrence rate between the LMAF group and the LIFT group in patients with single fistulas. Both techniques showed comparable efficacy when stratified by Parks classification(P>0.05).

LMAF reduces complications with a trend toward lower recurrence, and comparable anal functional outcomes to LIFT, though long-term efficacy requires further validation.