Magnetic Resonance Imaging Versus Sinogram in Evaluation of Perianal Sinus

Introduction: Perianal fistula is a commonly encountered disease, complete evaluation of which is essential to prevent recurrent surgery. Aim: The purpose of this study was to determine the role of magnetic resonance imaging (MRI) and sinogram in evaluation of perianal sinus and comparison between two investigations in pre-operative assessment of perianal fistulas. Materials and Methods: A prospective study was carried on 34 patients studied between the period of May 2015 and August 2016. Patients who had undergone X-ray sinogram followed by MRI non-contrast study were included in the present study. MRI sequences assessed including T2 weighted (T2W) sagittal, axial and coronal, short T1 inversion recovery (STIR) coronal and axial, T1W axial, and coronal sequences. Results: On MRI evaluation, out of 34 patients, 9 patients (26.5%) had only perianal sinus with no communication with the anal canal while 25 patients (73.5%) were diagnosed as perianal fistula. Out of these 34 patients, 5 were female and 29 were male patients. Of the 25 patients with fistula, 24 patients had fistulous communication with anal canal, and 1 patient had extrasphincteric fistula (Type 5 St. James University and Hospital and Type 4 Parks classification) tracking down from a pelvic abscess. Of these 25 fistula cases, 14 (56%) were simple and 11 (44%) cases were associated with branching course. On conventional sinogram out of 34 subjects, 20 cases were diagnosed as sinus and 14 were diagnosed as fistula and out of 20 cases of sinus tracts 11 cases were turned out to be fistula by MRI. Hence, out of 25 fistulas, only 56% (14 patients) of fistulas were picked up correctly. 44% (11 patients) of fistulas were falsely interpreted as sinus tracts. Conclusion: In our study, MRI proved to be a better investigation in the evaluation of perianal fistula in comparison to X-ray sinogram. T2W and STIR sequence have major role in determining detail anatomy of sinus track. Accurate pre-operative assessment of perianal fistula may help in reducing the recurrence and thereby reducing the number of repeated surgery.