Background: Contrast enhanced T1- weighted (CE-T1W) magnetic resonance imaging (MRI) is the preferred imaging modality for assessing perianal fistulae (PAF), it provides accurate detection and characterization of PAF. The study aims to assess the use of diffusion weighted MRI (DWMRI) alone as an alternative approach to CE-T1W-MRI and the identify optimal b-values in the obtained DWMRI for assessing anatomy and pathophysiology of PAF. Methods: 37 perianal fistula (PAF) patients who are in preoperative procedures with an average age of 40 ± 11.5 years, were recruited in this study. All patients were imaged on a 3.0 Tesla MRI scanner using CE-T1W sequence and DWMRI for b values of 50, 400, 800 and 1600 s/mm². The ratio of the mean region of interest (ROI) that is measured from 50% of the maximum for the lesion to a reference background in images of both approaches. Coefficient of variation was also applied in the assessment of the two approaches. The analyses were carried out using the Mann-Whitney U test. Results: ROI measurements were 203 ± 48 and 68 ± 24 in the ROI of the lesion, and 116 ± 20 and 31 ± 6 for the reference background ROI for CE-T1WMRI and DWMRI, respectively; the values were represented as mean ± STD. The lower b value (<100 s/mm²) of DWI reveals higher image resolution of the anatomical structures compared to higher b values; however, higher b values were better than lower b values in image contrast. The percentage of coefficient of variation was not statistically significantly different between CE-T1WMRI and DWMRI (p-value = 0.079). Conclusions: The findings show that DWMRI has statistically similar efficacy with respect to CE-T1WMRI in the diagnosis of PAF. Thus, this may suggest that DWMRI ought to be regularly included in typical MRI procedures for diagnosing PAF.

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