Diagnostic accuracy of body coil MRI in describing the characteristics of perianal fistulas

Objective The purpose of this study was to determine the accuracy of synergic body coil MRI using SPIR technique without contrast, in the determination of fistula characteristics in patients with clinically positive signs. Method and subjects This was a case-series prospective study including 29 consecutive patients with clinically suspected fistulas-in-ano. The standard synergic body coil was used and all patients had T2-weighted SPIR sequences. One radiologist, without prior knowledge of the clinical examination, analysed images and noted the presence of the fistula, its classification and the presence and number of any collections or extensions. The surgeon noted the MRI findings and looked for lesions suggested on MRI. The results of the MRI and surgical assessments were then compared. Results of surgical exploration while the surgeon was aware of MRI results were considered as the gold standard of surgical anatomy. Results Twenty-three (79.31%) of 29 fistula tracks were seen on MRI which correctly determined the type of all fistulas. In the six cases where the fistula was not seen on MRI, five were low trans-sphincteric and one was rectovaginal. MRI identified 8 of 10 collections. Conclusion The synergic body coil MRI with SPIR sequencing without endoanal coils had a high accuracy in the diagnosis of high fistulas collections, complex fistulas and extensions.