Abstract
Background: Perianal fistula (PAF) is an abnormal tract communicating an external cutaneous opening in the
perianal region to the anal canal. PAF is one of the common anorectal disorders in surgical practice with high
prevalence. The current study aimed to determine the ability of preoperative MRI for preoperative evaluation of
perianal fistula.
Results: This is a retrospective evaluation of 65 patients with perianal fistula. MRI fistula imaging-related data were
revised, and fistula severity was scored using criteria of both local extension of fistulas and active inflammation for a
total maximum score of 22. Preoperative MRI could predict the severity of perianal disease with sensitivity,
specificity, and accuracy rates of 75%, 92%, and 84.6%, respectively. Surgical findings concerning PAF severity
correlated significantly with MRI findings. Diffusion-weighted magnetic resonance imaging (DW-MRI) provided high
sensitivity and accuracy with 100% specificity for fistula visualization and highest sensitivity, specificity, and accuracy
for detection of cavities > 3mm in diameter. DW-MRI provided the highest specificity rate on ROC curve analysis
among the three MRI pulse sequences (DW-MRI, short tau inversion recovery (STIR), and T1 post-contrast).
Conclusion: MRI is valuable and accurate for preoperative investigation for PAF evaluation and abscess localization.
MRI allowed accurate detection of internal fistula opening and its relation to sphincters. DW-MRI is a valuable
sequence with highest diagnostic yield, and its addition to STIR WI improves sensitivity and specificity for
determination of fistula activity and extension. |
