Comparative Study of Lateral Internal Sphinterotomy versus Anal Advancement Flap in the Treatment of Chronic Anal Fissure: A Randomized Controlled Trial

Abstract

Background: Chronic anal fissure (CAF) is a common benign anorectal disorder characterized by severe pain during defecation, rectal bleeding, and impaired quality of life. Although lateral internal sphincterotomy (LIS) remains the standard surgical treatment because of its high healing rates, concerns regarding postoperative fecal incontinence have encouraged the development of sphincter-preserving procedures such as anal advancement flap (AAF). This study aimed to compare the short-term clinical outcomes of LIS and AAF in the management of chronic anal fissure.

Methods: A randomized controlled trial was conducted in the Department of Surgery, Nishtar Medical University and Hospital, Multan, Pakistan. A total of 142 patients with chronic anal fissure were randomly allocated into two equal groups: Group A underwent lateral internal sphincterotomy (n = 71), while Group B underwent anal advancement flap surgery (n = 71). Patients were followed for eight weeks after surgery. Primary outcome measures included symptom resolution, complete fissure healing, and fecal incontinence assessed using the Wexner Fecal Incontinence Score. Secondary outcomes included postoperative wound infection and recurrence. Statistical analysis was performed using SPSS version 26, and a p-value ≤0.05 was considered statistically significant.

Results: The estimated mean age was 36.0 ± 12.2 years in the LIS group and 35.5 ± 11.8 years in the AAF group, with comparable baseline demographic characteristics between the groups. Symptom resolution was achieved in 51 (71.8%) patients undergoing LIS compared with 63 (88.7%) patients treated with AAF (p = 0.01). Complete fissure healing at eight weeks occurred in 56 (78.9%) patients in the LIS group and 67 (94.4%) patients in the AAF group (p = 0.006). Postoperative fecal incontinence was significantly lower following AAF than LIS (1.4% vs. 14.1%; p = 0.005). Although postoperative wound infection (5.6% vs. 12.7%) and recurrence (2.8% vs. 9.9%) were less frequent after AAF, these differences were not statistically significant.

Conclusion: Anal advancement flap demonstrated superior short-term clinical outcomes compared with lateral internal sphincterotomy, with significantly higher rates of symptom resolution and fissure healing and a markedly lower incidence of postoperative fecal incontinence. As a sphincter-preserving procedure, AAF represents a safe and effective surgical alternative for the treatment of chronic anal fissure, particularly in patients at increased risk of continence impairment.