Magnetic Resonance Imaging Evaluation of Perianal Fistulas

Abstract

Purpose

The purpose of this study was to discuss the usefulness of magnetic resonance imaging in evaluating perianal fistulas, their ramifications, extent, associated abscesses and relations with the anal sphincter complex and its role in preoperative classification.

Material & methods

A retrospective study was carried out using picture archiving and communication system. Data of 58 patients presented with a clinical suspicious of perianal fistula from April 2012 to March 2013 was collected. In all patients pre contrast T2 propeller with and without fat suppression, diffusion weighted and pre and post contrast liver acceleration volume acquisition sequences were obtained. Pulse sequences were as follows: T2 propeller (TR: 7766 ms, TE: 122 ms), Diffusion weighted (TR: 7000 ms, TE: 67 ms), LAVA (TR: 7 ms, TE: 3.242 ms).

Results

MRI revealed a total number of 38 fistulae in 35 (60%) patients while 13 (22%) patients had only perianal sinuses. Out of these 35 patients, 4 were females and 31 were male subjects. Out of total 38 fistulae seen in these 35 patients, 11 (29%) were transsphincteric, 24 (63%) were intersphincteric and 2 (5%) were suprasphincteric. Only 1 (3%) case was extrasphincteric fistula. Twenty-six fistulae (68%) were simple, whereas 12 (32%) showed associated abscess formation, inflammation and branching course.

Conclusion

Our results support that MRI is the method of choice for evaluating perianal fistulae as they display the anatomy of the sphincter muscles orthogonally with a background of good contrast resolution. Moreover, with MRI we can accurately classify perianal fistulas preoperatively along with the detection of associated infection and help in planning a successful surgery.