Abstract
Background Magnetic resonance imaging (MRI) is the imaging modality of choice for evaluating
perianal fistulae, due to its ability to show the relationship of perianal fistulae
with anal sphincters, fistula extensions, secondary ramifications and associated complications.
Aim To evaluate the role of diffusion-weighted MRI in the evaluation of perianal fistulae.
Settings and Design A hospital-based cross-sectional study.
Materials and Methods The study group composed of 47 patients of perianal fistula. MRI with diffusion-weighted
imaging (DWI) was performed with Philips 0.5 T Ingenia scanner. DWI with different
b-values (b = 50, b = 400, and b = 800 smm2) were obtained. The MRI findings were correlated with local clinical examination
and or surgical findings.
Statistical Analysis Used Chi-square test, independent samples t-test, and receiver operating characteristic curve analysis.
Result Fifty-nine perianal fistulas in 47 patients were included in the study sample. The
visibility of perianal fistula on DWI was less than T2-weighted (T2W) and combined
DWI-T2W images. Distinctly visualized (visibility score 2) perianal fistulas were
observed in 47 fistulas (79.6%) on DWI, 54 (91.5%) on T2W, and 58 (98.3%) on DWI-T2W
images. The mean of apparent diffusion coefficient (ADC) values of active fistula
was 0.972 ± 0.127 [SD] 10−3 mm2/s and inactive was 1.232 ± 0.185 [SD] 10−3 mm2/s with a significant difference (p-value < 0.0005). A cut-off mean ADC value of 1.105 × 10−3 mm2/s was used to differentiate active from the inactive fistula with a sensitivity of
87.5% and specificity of 73.3%.
Conclusion Combined DWI-T2W evaluation had a better performance in the detection of fistula
than DWI or T2W alone. DWI with mean ADC calculation had a good performance in differentiating
active from the inactive fistulas.
Keywords
intersphincteric - magnetic resonance imaging - perianal fistulae - transsphincteric
