Preliminary utilization of high-resolution direct MRI fistulography with hydrogen peroxide in diagnosing anorectal fistula: A retrospective study

Abstract

Abstract Background Fistula-in-ano is an abnormal tunnel formation linking the anal canal with the perineum and perianal skin. Multiple imaging methods are available to evaluate it, among which magnetic resonance imaging (MRI) is the most advanced noninvasive preoperative method. However, it is limited in its visualization ability. Therefore, this study aimed to investigate the feasibility of using a specific mixture of 3% hydrogen peroxide (HP) and gadolinium as a direct contrast agent for high-resolution HPMRI of perianal fistula. Additionally, it investigated the value of this new method for preoperative examination of complex or recurrent fistula via a preliminary study. Methods Preoperative physical examination, conventional ultrasonography, MRI plain scan, and high-resolution direct HPMRI fistulography data from nine patients with surgically confirmed complex or recurrent fistula-in-ano were retrospectively analyzed. We also assessed the detection rates of fistula tracks and their associated internal openings, including the connection between them and the internal and external anal sphincters. Furthermore, the detection of perianal abscess was analyzed relative to the intraoperative observations. Results Surgical confirmation revealed nine cases of anal fistula, including 17 internal openings, 18 fistula tracks, 21 external openings, and six perianal abscesses. ROC curve analysis revealed that the effectiveness of the physical examination, conventional ultrasound, and MRI plain scans for detecting internal openings was lower than that of high-resolution direct HPMRI fistulography (Z = 3.739, 2.642, 2.642, all p < 0.05). The efficacy of physical examination and conventional ultrasound in detecting fistula tracks was lower than that of high-resolution direct HPMRI fistulography (Z = 2.394, 2.503, all p < 0.05). The effectiveness of physical examination in detecting perianal abscess was inferior to that of high-resolution direct HPMRI fistulography (Z = 3.417, p < 0.05). No statistically significant difference was observed in the ability of MRI plain scan to detect fistula tracks or in the capacity of conventional ultrasound to detect perianal abscesses than that of high-resolution direct HPMRI fistulography. Conclusions This novel high-resolution direct HPMRI fistulography technique enhances the visualization of recurrent and complex fistula-in-ano, enabling visualization of branched fistulas, thereby improving surgical outcomes.