Role of Ultrasonography in the Evaluation of Perianal Fistula and Sinus: A Prospective Observational Study

Background: Perianal fistula is a common anorectal condition resulting from chronic infection of the anal glands and is often associated with recurrent discharge, pain, and abscess formation. Accurate preoperative identification of the fistulous tract, internal opening, and associated extensions is essential for effective surgical management and prevention of recurrence. Imaging modalities play a significant role in delineating fistula anatomy. Ultrasonography (USG), including transperineal and endoanal approaches, has emerged as a useful, non-invasive, and cost-effective imaging technique for evaluating perianal fistulas. Objective: To evaluate the role of ultrasonography in detecting primary tracts, internal openings, secondary tracts, and associated abscesses in patients with perianal fistula and sinus, and to compare ultrasonographic findings with surgical findings. Methods: This prospective observational study included 140 patients clinically suspected to have perianal fistula or sinus. Ultrasonographic examination of the perianal region was performed using high-resolution probes. Parameters evaluated included visualization of the primary tract, identification of internal openings, detection of secondary tracts, abscess formation, and horseshoe extensions. Ultrasonographic findings were subsequently compared with intraoperative surgical findings to determine diagnostic accuracy. Results: The mean age of patients was 39.2 ± 11.5 years, with a male predominance (male:female ratio 4:1). Perianal discharge was the most common symptom (85%), followed by pain (74.3%). Ultrasonography visualized the primary tract in 88.6% of patients, internal opening in 69.3%, secondary tracts in 72.1%, abscesses in 66.4%, and horseshoe extension in 27.1% of cases. Comparison with surgical findings showed high diagnostic performance, with sensitivity of 92.5% for primary tract detection and overall diagnostic accuracy ranging from 81.4% to 89.3%. Conclusion: Ultrasonography is a reliable, non-invasive imaging modality for evaluating perianal fistula and sinus. It provides accurate anatomical delineation of fistulous tracts and associated complications, thereby aiding in surgical planning and improving treatment outcomes.