[Value of magnetic resonance diffusion-weighted imaging for evaluating the inflammatory activity of perianal Crohn's fistula].

OBJECTIVE: To explore the value of magnetic resonance diffusion-weighted imaging (MR-DWI) for evaluating inflammatory activity of perianal Crohn's fistula.
 Methods: A total of 55 patients, who were diagnosed as perianal Crohn's fistula by surgery and/or endoscopy, were assessed retrospectively. All patients, underwent pelvic magnetic resonance imaging (MRI) before and 32 weeks after the treatment, were divided into 2 groups according to their response to treatment: an effective group (34 cases) and an ineffective group (21 cases). The MRI images of patients in the 2 groups were analyzed. The changes of apparent diffusion coefficient (ADC) values before and after treatment in the 2 groups were measured and compared by a paired t-test. An MRI-based score of perianal Crohn's disease severity was calculated as a reference standard, and the correlation between the ADC value and the MRI-based score was analyzed by using a Pearson correlation coefficient method.
 Results: In the effective group, the ADC values after therapy were significantly greater than those before therapy (P 0.05). There was a strong negative correlation between the ADC values (after and before therapy) and the MRI-based scores in all the patients [in the effective group alone (r=-0.672, P<0.01) or in the effective group + the ineffective group (r=-0.638, P<0.01)].
 Conclusion: Changes in the ADC values of perianal fistula are related to the fistula activity. MR-DWI and ADC value can accurately evaluate the inflammatory activity of perianal Crohn's fistula.