Diagnostic Accuracy of Mr Fistulogram in the Evaluation of Perianal Fistulas: Correlation with Surgical Findings

Background: Perianal fistulas are complex anorectal disorders characterized by abnormal tracts between the anal canal and perianal skin, often with secondary extensions and hidden openings. Accurate preoperative mapping is crucial for successful surgical treatment and to prevent recurrence. While MRI fistulography is emerging as the gold standard imaging modality, its diagnostic accuracy must be validated against intraoperative findings. Aim: To evaluate the diagnostic accuracy of MR fistulogram in detecting the anatomical details of perianal fistulas, and to correlate its findings with surgical observations. Methods: This prospective observational study was conducted on 70 patients with clinically diagnosed perianal fistulas at Rabindranath Tagore Medical College, Udaipur, between January 2024 and July 2025. All patients underwent preoperative MR fistulography followed by definitive surgical management. MRI findings were assessed for external and internal openings, secondary tracts, abscesses, and classified according to Parks and St. James’s systems. Surgical findings served as the reference standard. Diagnostic parameters such as sensitivity, specificity, and kappa agreement were calculated. Results: The majority of patients were males (82.8%) with a mean age of 35.6 years. Intersphincteric fistulas were most common (75.7%). MR fistulogram showed high sensitivity and specificity for detecting internal openings (85.2% and 100%, respectively) and external openings (85.7% and 100%, respectively). MRI identified more abscesses (22.8%) than surgical exploration (12.8%), with moderate agreement (κ = 0.47). Almost perfect agreement was observed for St. James grading (κ = 0.94) and internal openings (κ = 0.82), while external openings showed substantial agreement (κ = 0.72). Conclusion: MR fistulography is a highly accurate, non-invasive modality for evaluating perianal fistulas. It demonstrates strong concordance with surgical findings for key anatomical features, especially internal and external openings and fistula grading. MRI should be routinely incorporated into the preoperative workup of both simple and complex perianal fistulas to improve surgical outcomes and reduce recurrence rates.