THE DIAGNOSTIC ACCURACY OF ENDOANAL ULTRASONOGRAPHY IN FISTULA-IN-ANO: AGREEMENT WITH INTRAOPERATIVE FINDINGS IN A TERTIARY CARE HOSPITAL, LAHORE

Abstract

Background: Fistula-in-ano is a common anorectal disorder with significant morbidity and recurrence risk. Accurate preoperative mapping of the fistula tract and internal opening is essential for successful surgical management. Magnetic Resonance Imaging (MRI) is considered the gold standard but is often limited by cost and availability in low-resource settings. Endoanal ultrasonography (EAUS) offers a practical, cost-effective alternative. This study aimed to evaluate the diagnostic accuracy and agreement of EAUS with intraoperative findings in patients with fistula-in-ano.

Methods: A cross-sectional study was conducted on 96 patients diagnosed with fistula-in-ano at Sheikh Zayed Hospital, Lahore, over six months. All patients underwent preoperative EAUS followed by surgical exploration, which served as the reference standard. Fistula parameters—including tract course, internal opening localization, and presence of secondary tracts or abscesses—were documented. Diagnostic performance indices (sensitivity, specificity, PPV, NPV, and accuracy) were calculated, and agreement between EAUS and intraoperative findings was assessed using Cohen’s kappa statistic.

Results: The mean patient age was 38.4 ± 11.6 years; 72.9% were male. The most frequent fistula types were intersphincteric (41.6%) and transsphincteric (36.4%). EAUS correctly identified the tract course in 86.4% and localized the internal opening in 88.5% of cases. Sensitivity, specificity, and accuracy for internal opening detection were 88.9%, 82.3%, and 85.4%, respectively, with substantial agreement (κ = 0.74) between EAUS and intraoperative findings. Overall diagnostic accuracy was 85.4%. Postoperative complications occurred in 15.6% of patients, with 3.1% recurrence within six months.

Conclusion: EAUS demonstrated high diagnostic accuracy and strong agreement with intraoperative findings in assessing fistula-in-ano. Given its accessibility, affordability, and reliability, EAUS serves as an effective first-line imaging modality for preoperative evaluation, particularly in resource-limited settings where MRI is unavailable. Larger multicenter studies with long-term follow-up are warranted to validate these findings.