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Article Type

Original Study

Abstract

Objective The aim of this study was to clarify the role of MRI in the diagnosis and classification of perianal fistula and to evaluate the additional clinical value of preoperative MRI and its benefit to the surgeon. Background An anorectal abscess originates from an infection arising in the cryptoglandular epithelium lining of the anal canal that can penetrate through the internal sphincter. Extension of the infection can involve the intersphincteric space, ischiorectal space, or even the supralevator space. Patient and methods This prospective study included 20 (15 men and five women; age range: 19–59 years; mean age: 36.85 years) patients selected from 34 patients referred to the Radiodiagnosis Department with clinically suspected perianal fistula. The study was conducted between March 2013 and November 2015 after preoperative clinical examination. Pulse sequences used were STIR, T2WI, T1WI, and T1WI after contrast with fat suppression sequences in axial, coronal, and, sometimes, sagittal planes. Results MRI revealed six (30%) patients with grade 1 simple linear intersphincteric fistula, five (25%) with grade 2 intersphincteric fistula with abscess or secondary track, three (15%) with grade 3 trans-sphincteric fistula, four (20%) with grade 4 trans-sphincteric fistula with abscess or secondary track, and two (10%) with grade 5 supralevator and translevator disease. One of the two supralevator fistulae showed horseshoe extension. MRI findings were concordant with the surgical findings in 18 (90%) patients (P = 0.003). Fallacies of MRI were observed in two (10%) patients, which proved to be sinus at surgery. Conclusion Our results support that MRI is the imaging technique of choice for preoperative evaluation of perianal fistulae, providing a highly accurate, rapid, and noninvasive means of performing presurgical assessment as it displays the anatomy of the sphincter muscles orthogonally with a background of good contrast resolution.

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