Magnetic resonance imaging and peroxide-enhanced anal endosonography in assessment of fistula in anus: comparison with surgery
Background: Although there are numerous modalities to evaluate perianal fistula, there is still a need to determine the most sensitive, specific, and accurate modality. This study was conducted to determine the performance characteristics of magnetic resonance imaging (MRI) and contrast-enhanced three-dimensional endoanal ultrasonography (C-3DEAUS) considering surgery as the gold standard.
Methods: A total of 36 patients who were diagnosed of having anal fistula with 10-MHz hydrogen peroxide-enhanced three-dimensional EAUS underwent MRI followed by surgery. Both of tests were done the day before surgery. Fistula classification was determined with each modality according to Parks’ criteria as inter-sphincteric, trans-sphincteric, extra-sphincteric, or supra-sphincteric and was compared with the surgical findings in all patients. If the accuracy of each modality was at least 85 % compared with the surgery, it was considered as clinically useful.
Results: Agreement for the classification of the primary fistula tract was 94.3 % for C-3DEAUS and surgery, 97.1 % for MRI and surgery. Considering a clock face, C-3DEAUS and surgery agreed in location of internal opening in 88.6 % of cases while MRI and surgery agreed in 97.1 %. In detection a collection, agreement between C-3DEAUS and surgery was 82.9 %, and 97.1 % between MRI and surgery.
Conclusions: Both methods had almost perfect agreement with surgical findings in the classification of the primary fistula tract but MRI had more agreement in distinguishing other aspects of a fistula and it can be used as the most reliable method for preoperative evaluation of perianal fistulas.
Assoc. Prof. M. Ghafoori, Assoc. Prof. B. Mahjoubi, Assist. Prof. H. Youseffam, M. Mollabashi, H. Nikbakht, European Surgery 1/2016