MRI Before Fistula Surgery: Will It Change the Operation?—a Prospective Study

The last word in anal fistula surgery has not been written. The literature is unclear on which patient should undergo a pre-operative magnetic resonance imaging [MRI]. Most guidelines are clear that complex and recurrent fistulae, or those with a background of inflammatory bowel disease, should undergo an MRI evaluation, but otherwise the guidelines are hazy and ill defined. In this study, over a 3-month period, all patients who clinically presented with anal fistula underwent MRI of the ano-rectal region. The clinical findings on digital rectal examination [DRE] were compared to the final radiological diagnosis, and the peri-operative findings. The fidelity of the MRI diagnosis was the endpoint of the analysis, as was the impact on the operative strategy. A change in operative course was brought about by the MRI, in a percentage of 16.1% which is quite significant. None of the patients had an endo-anal ultrasound as it is not part of our protocol. It is concluded that the addition of the MRI changed the surgical approach in a significant proportion of patients with fistula in ano and consequently it is now part of our regular workup of every anal fistula patient, to do an MRI preoperatively. By adding MRI, our recurrence rates came down significantly which is quite evident in the follow-up.