E-ISSN 1305-3612
1 Department of General Surgery, Hacettepe University School of Medicine, Ankara, Turkey  
2 Department of Radiology, Hacettepe University School of Medicine, Ankara, Turkey  
Diagn Interv Radiol ; : -

Abstract

PURPOSE: An anal fistula is an abnormal tract or cavity between the anal canal and the perianal skin. The surgical treatment of anal fistulas requires identification the course of the primary and secondary tracts and their relation with the sphincteric musculature in order to manage them properly and drain any abscess. Physical examination alone is not as accurate as imaging modalities in detecting these features of the fistula and recurrences are usually due to missed or inadequately managed of infective components. MRI is the preferred imaging modality in anal fistulas but which patient group should have a preoperative MRI is a matter of debate. The aim of this study was to determine the effect of MRI on surgical management of the anal fistulas.


METHODS
: Medical records of patients who had surgery for primary anal fistula and MRI preoperatively in our University Hospitals from 1st of January 2008 to 15th April 2018 were collected anonymously and retrospectively. Any discrepancies between operative findings and MRI reports were noted. Two study groups were formed as per the contribution of the preoperative MRI, the “significant” and “non-significant” contribution groups. The significant contribution group identified patients with (i) secondary (blind) tracts, (ii) horseshoe fistulas, or (iii) abscesses undiagnosed at physical examination and EUA, (iv) if the location of the internal orifice was different from that identified by physical examination or (v) if the grade of the fistula was assessed to be more advanced after preoperative MRI.


RESULTS
: Total number of operations was 136. Mean age of patients was 43 ± 13. 106 patients were male. 47 cases suffered from recurrent fistula. MRI contribution to clinical evaluation was found to be significant in %33.8 of the cases. MRI provided significant information more for complex fistulas than simple fistulas The significant preoperative MRI contribution was also more frequent if the external opening was more than 2 cm away from anal or when a horseshoe fistula was present.


CONCLUSION
: Our study is valuable in linking physical examination findings with preoperative MRI. The distance of the external opening from the anus was not studied in the literature and our findings support the use of MRI for fistulas with external opening located more than 2 cm from the anus. These fistulas also tend to be complex and have higher grade. In recurrent cases MRI contributes not only by establishing the fistula anatomy but also identifying possible sphincter damage.

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