A comparison of trans-fistula contrast-enhanced endoanal ultrasound and MRI in the diagnosis of anal fistula.

Abstract

Many hospitals favor magnetic resonance imaging (MRI) as the preferred diagnostic method to detect anal fistula, trans-fistula contrast-enhanced ultrasound (CEUS) for the diagnosis of anal fistula have attracted the attention of investigators worldwide. This study aimed to investigate the efficacy of trans-fistula contrast-enhanced endoanal ultrasound (CEUS) and magnetic resonance imaging (MRI) in the diagnosis of anal fistula. Ninety-eight patients undergoing trans-fistula CEUS and MRI were retrospectively analyzed. The fistulous trend and positional relation between the fistula, levator ani muscle, and sphincter (Parks classification), as well as the numbers of fistulous branches, number and position of the fistula, and distance between internal opening and anal edge were recorded. These parameters were compared with the postoperative results. There were no significant statistical differences (P>0.05) in the accuracy rates of trans-fistula CEUS and MRI, respectively, in terms of Parks classification (90.82%, 92.86%), branches (89.19%, 81.08%), internal openings (92.68%, 89.43%), and internal openings ≥3 cm from the anal edge (85.71%, 92.86%). However, we observed a significant difference in terms of internal openings <3 cm from the anal edge (96.30%, 87.65%) (P=0.043). Although both methods exhibited a perfect accuracy rate in diagnosing anal fistula, trans-fistula CEUS displayed superior diagnostic value for internal openings <3 cm from the anal edge, and could provide reliable pre-operative evidence.