Objective To investigate the accuracy of preoperative pelvic magnetic resonance imaging combined with intraoperative injection of hydrogen peroxide solution to locate the internal orifice and its surgical efficacy for anal fistula.

Methods A total of 86 patients with anal fistula admitted to Sir Run Run Hospital Affiliated to Nanjing Medical University were selected as study objects, and were randomly divided into observation group (43 cases) and control group(43 cases). All patients underwent pelvic 3.0T pelvic magnetic resonance imaging examination before operation. The fistula distribution was assessed. In the observation group, hydrogen peroxide solution was slowly injected through the external opening to locate the internal opening of anal fistula. The control group used traditional anal fistula probe combined with digital rectal examination to locate the internal opening of anal fistula. The accuracy of intraoperative positioning of the internal orifice of anal fistula in the two groups and the accuracy of the internal orifice positioning in complex anal fistula cases were compared. Visual Analog Scale (VAS) was used to evaluate the wound pain of patients 1 week after surgery, and the number of postoperative recurrent anal fistulas, postoperative wound healing time and the incidence of wound complications were compared between the two groups.

Results The positioning accuracy rate of the anal internal opening in the observation group was higher than that in the control group, and the difference was statistically significant (P < 0.05). The number of complex anal fistula in patients in the observation group was more than that in the control group(10 cases versus 4 cases, P < 0.05). One week after surgery, VAS score of observation group was (1.53±0.91), which was lower than (2.28±0.98) in the control group, and the difference was statistically significant(P < 0.05). The wound healing time in the observation group was shorter than that in the control group (25.37±3.86) d versus (29.05±2.62) d, P < 0.05.

Conclusion Preoperative pelvic magnetic resonance imaging combined with intraoperative injection of hydrogen peroxide solution is accurate in locating the internal orifice of anal fistula, can relieve the pain of patients′ wounds, and reduce the incidence of postoperative complications, therefore, it is beneficial to wound healing.