Comparison of multi-phase contrast-enhanced T1-weighted volumetric interpolated breath-hold examination and fat-suppressed T2-weighted combined with diffusion-weighted magnetic resonance imaging in anal fistula evaluation.

Anal fistula is a common anorectal disorder that significantly diminishes the quality of life for affected patients. Accurate preoperative evaluation of the fistula's traits is essential for customizing surgical strategies, improving patient outcomes, and reducing the likelihood of the disease returning. This study aimed to evaluate the diagnostic accuracy of multi-phase contrast-enhanced fat-suppressed T1-weighted imaging using three-dimensional gradient echo sequence volumetric interpolated breath-hold examination (CE-FS-T1-3D-VIBE) and fat-suppressed T2-weighted imaging combined with diffusion-weighted imaging (FS-T2WI-DWI) sequence in delineating the characteristics of anal fistulas. A case-control study of 168 patients with anal fistula was conducted through the picture archiving and communication systems (PACS; diagnostic imaging workstation). Imaging evaluations were performed using both multi-phase CE-FS-T1-3D-VIBE and FS-T2WI-DWI imaging on a Siemens 3.0T magnetic resonance imaging system (Skyra 3.0T superconducting type). The efficacy of each imaging modality in depicting the clarity, number, and positioning of the internal openings, as well as the identification of primary and secondary fistulas and abscesses, was independently evaluated in a blinded manner by two senior diagnostic radiologists, each with over a decade of experience. Statistical analyses were performed using χ2 test. Comparative analysis of the FS-T2WI-DWI and multi-phase CE-FS-T1-3D-VIBE sequences for diagnosing internal and primary fistula tract clarity demonstrated a significant superiority of the multi-phase CE-FS-T1-3D-VIBE sequence in delineating internal clarity (P=0.013) and primary fistula tract clarity (P<0.001). The multi-phase CE-FS-T1-3D-VIBE sequence demonstrated superior accuracy over the FS-T2WI-DWI sequence in depicting localization of internal openings [86.31% vs. 77.38%, 95% confidence interval (CI): 0.307-0.959, P=0.034], as well as delineation of the secondary tracts (88.69% vs. 80.95%, 95% CI: 0.293-1.001, P=0.048). Despite the increased accuracy of the multi-phase CE-FS-T1-3D-VIBE sequence, no difference was observed between the two imaging techniques regarding the accuracy in determining the number of internal openings, the quantity of primary fistulas, and the classification of anal fistulas. This study elucidates that the multi-phase CE-FS-T1-3D-VIBE imaging sequence potentially represents a more effective noninvasive alternative for the precise evaluation of the positioning and clarity of the internal opening, as well as the delineation of primary and secondary fistula tracts in anal fistula patients, compared to the FS-T2WI-DWI sequence. This enhanced diagnostic capability underscores the utility of multi-phase CE-FS-T1-3D-VIBE in improving the clinical management of anal fistulas.