Comparative analysis of MR imaging findings of perianal fistulas in patients with and without Crohn disease

Objective To investigate the differences in magnetic resonance imaging characteristics between perianal-fistulas of Crohn disease (P-FCD) and perianal-fistulas of non-Crohn disease (P-FNCD). Methods A retrospective analysis was made of 109 patients with perianal fistula who were confirmed by clinical examinations and surgery and had complete preoperative pelvic MRI data from sir run run shaw hospital affiliated to Zhejiang University from June 2015 to March 2017. Patients were divided into P-FCD and P-FNCD groups according to whether the patient was clinically diagnosed with Crohn disease(CD).There were 59 cases in group P-FCD and 50 cases in group P-FNCD. All patients underwent pelvic MRI plain scan and enhanced scan. the classifications of perianal fistula (St. James University Hospital classification and improved Parks classification) were evaluated. The number of branches, the number of abscesses, the number of internal opening, the height of the internal opening were measured and recorded. The incidence of proctitis and anal inflammation were recorded. Van Assche score was evaluated. Measured data between patients in the P-FCD and P-FNCD groups were compared using independent sample t test (normal distribution) or non-parametric test (skewed distribution).The quantitative data were compared using cross-sectional Pearson χ2 test. Results There were significant differences in the number of branches, the number of abscesses, the number of internal opening, the height of the internal opening, the positive rate of proctitis, the positive rate of anal canalitis, and the Van Assche score between the P-FCD group and the P-FNCD group (all P 0.05).There was significant difference in the classification of St. James University Hospital between the P-FCD group and the P-FNCD group (P<0.05). Conclusions P-FCD is mainly composed of high complex anal fistula, which is significantly different from P-FNCD. We used St. James University Hospital classification and Van Assche score to diagnose perianal fistula in combination with clinical examinations, which was helpful for the diagnosis of P-FCD. Key words: Crohn disease; Perianal fistulas; Magnetic resonance image