Role of magnetic resonance imaging in detection and characterization of perianal fistula

Background: Perianal fistula is a common but fairly complicated condition, which needs in-depth evaluation of the fistula track for proper treatment and complete cure. Clinical examination does play its significant role; however, the ramifications of track, blind ending tracks, and secondary collections are some blind points for the clinicians which are very well-demonstrated by magnetic resonance imaging (MRI). Surgical planning for complete cure of perianal fistula is highly dependent on the grade and associated complications of fistula. Aims and Objectives: The objective of our study is to – (i) evaluate the role of MRI in detection as well as characterization of perianal fistula; (ii) classify and grade the perianal fistula according to the “St. James University Hospital grading scheme” and the “Park’s classification;” and (iii) evaluable the perianal fistula as per the following: Internal opening of the track; high versus low lying perianal fistulae; transsphincteric/extra sphincteric/supralevator extension of the fistula; secondary tracts/ramifications/impending fistulae; and ischioanal abscess/ischiorectal abscesses/horseshoe collection. Materials and Methods: An observational type of study was conducted over a duration of 24 months. Patients with suspected perianal fistulae with one or many external openings were prospectively selected for MRI evaluation of their fistula tracks. MRI findings were then evaluated according to “St. James’s University Hospital MR Imaging Classification of Perianal Fistulae.” Results: Out of 30 clinically diagnosed patients, all patients demonstrated presence of perianal fistula. Out of total 30 patients, majority had external opening at 7 O’clock position (33.3%) followed by 5 O’clock position (26.6%). Out of total 30 patients, majority had internal opening at 6 O’clock position (43.3%) followed by 3 O’clock position (13.3%). Conclusion: MRI imaging of perianal fistula is a simple and non-invasive method and is extremely useful for the surgical planning. It has a definite place in imaging of complex perianal disease as it provides high resolution images of perianal region anatomy, allowing characterization, classification, and grading of the fistula. This thus guides in the surgical decision making and helps in successful treatment of disease.