ObjectiveTo investigate effect of preoperative three-dimensional anorectal endosonography (3D-AREUS) in anal fistula surgery.MethodsA total of 100 patients with anal fistula who were admitted to the Chaoyang Central Hospital from December 2017 to December 2018 were included prospectively, then were randomly divided into ultrasound group and control group with 50 cases in each group. The preoperative examination was performed by 3D-AREUS in the ultrasound group, and preoperative routine examination, finger examination or probe exploration were performed in the control group. The postoperative recurrence and anal functions were compared between the two groups.ResultsThere were no statistically significant differences in the gender, age, body mass index, anal surgery history, preoperative anal function, etc. between the two groups (P>0.05). The detection rate of branch fistulas in the ultrasound group was significantly higher than that in the control group (P=0.025). For the patients with complex anal fistula, compared with the control group, the location accuracy rate of internal opening was higher (P=0.014), the change value of preoperative and postoperative fecal incontinence score was lower (P=0.039), anorectal pressure status (resting pressure of anal canal, anal systolic pressure, and length of anal high pressure zone) were lower (P<0.05) in the ultrasound group; For the patients with simple anal fistula, which had no significant differences between the ultrasound group and control group (P>0.05). There were 4 cases of recurrence in each group.ConclusionsFor complex anal fistula, preoperative 3D-AREUS could clarify position of internal opening, presence of branching fistula, and the relationship between fistula and sphincter, so as to make accurate surgical plans, reduce secondary injuries, and retain postoperative anal function of patients.