Evaluation of unenhanced three-dimensional endoanal ultrasound scan in preoperative assessment of perianal sepsis

Abstract

Background: Perianal sepsis which includes perianal fistula and abscess is a common clinical condition that requires thorough preoperative evaluation to decrease the recurrence rate and to plan relevant surgery according to the anatomy of the fistula. MRI and 3D EAUS are two important preoperative investigations that delineate the anatomy of simple and complex fistula tracts. Due to lower cost and easier use 3D EAUS is a safe and reliable first-line investigation in evaluating perianal abscess. Methods: This is a retrospective and prospective analysis of patients with perianal sepsis who underwent pre-operative unenhanced 3D-EAUS in the departments of Colorectal surgery, Gastrointestinal surgery, and General surgery in our hospital. A B-K medical 2052 transducer was used for the study and the surgical assessment was done by multiple surgeons from multiple departments. Results: A total of 255 patients were assessed. The accuracy for primary fistula tracts and internal opening was 83.53% and 88.62% respectively. The kappa coefficient of correlation was k=0.70 (substantial agreement) for the fistula tract and k=0.81 (near perfect agreement) for the internal opening. The sensitivity, and specificity of primary tracts and internal openings were calculated. Transphincteric fistulas were 57% in our study. Conclusions: Unenhanced 3D EAUS is a reliable first-line investigation in preoperative evaluation of perianal fistula and abscess. Transphincteric fistula is the most common type of fistula. There is a high chance of correlation for the primary tract if a non-colorectal specialist performs the fistula surgery after 3D-EAUS without blinding.