Diagnostic Accuracy of Magnetic Resonance Imaging for Perianal Fistula Tract Using Operative Findings as the Gold StandardDiagnostic Accuracy of Magnetic Resonance Imaging for Perianal Fistula Tract Using Operative Findings as the Gold Standard

Abstract

Background: Perianal fistula is a chronic inflammatory condition that causes pain, discharge, and recurrent sepsis. Accurate preoperative delineation of fistula anatomy is essential for appropriate surgical management. Magnetic resonance imaging (MRI) provides high-resolution assessment of the perianal region; however, its diagnostic accuracy requires evaluation against operative findings. Aim: To determine the diagnostic accuracy of MRI for identifying perianal fistula tracts using intraoperative findings as the reference standard. Materials and Methods: A cross sectional diagnostic accuracy study was conducted in the Department of Diagnostic Radiology, Lahore General Hospital, Lahore, over six months June 2024 to December 2024 after ethical approval. Non probability consecutive sampling was used to enroll 150 patients aged 18 to 70 years with clinical suspicion of perianal fistula. MRI was performed on a 3.0 Tesla scanner using non enhanced T1 weighted and T2 weighted sequences. Images were interpreted by a consultant radiologist and correlated with intraoperative findings. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were calculated with 95% confidence intervals using a 2×2 table. Results: The mean age was 38.4 ± 11.2 years, and mean weight was 72.6 ± 9.8 kg. There were 98 males (65.3%) and 52 females (34.7%). MRI identified fistula in 128 patients (85.3%), while operative findings confirmed fistula in 132 patients (88.0%). True positives were 116, false positives 12, false negatives 16, and true negatives 6. Sensitivity was 87.9% (95% CI: 81.2%–92.8%), specificity 33.3% (95% CI: 13.3%–59.0%), positive predictive value 90.6% (95% CI: 84.3%–95.0%), negative predictive value 27.3% (95% CI: 10.7%–50.2%), and diagnostic accuracy 81.3% (95% CI: 74.1%–87.3%). Conclusion: MRI demonstrated high sensitivity and positive predictive value for perianal fistula detection, supporting its role in preoperative evaluation, while limited specificity indicated the need for operative correlation.