P575 A new tool for the surveillance of Crohn's perianal fistulae

Abstract

Background: Magnetic Resonance Imaging (MRI) is the tool used to assess response to medical therapy for the treatment of perianal Crohn’s fistulae. Quantifying fistula volumes would be more beneficial than relying on subjective MRI reports. We aim to use computer software and MRI segmentation to design 3D models of fistula tracks and measure baseline and post-biologics treatment fistula volumes. Methods: Ten baseline and post-biologics MRI images of Crohn’s perianal fistulae were randomly selected. Three-Dimensional fistula models were independently created by a surgeon and radiologist • Manual fistula volumes were calculated for each patient and the results compared • Data were obtained on Perianal Disease Activity Index (PDAI) scores, clinical and radiological healing for these patients. Data were analysed using Spearman’s correlation to determine whether a change in fistula volume over a one-year period correlated with a change in PDAI score over the same time period. Fistula volumes and PDAI score were also correlated with degrees of clinical healing. Results: Baseline volumes for the surgeon showed a median of 9766mm3 (IQR 4636, 30980). Post-biologics volumes had a median of 4200mm3 (IQR 2720, 20070). A change in baseline and post-treatment volumes was also observed by the radiologist; the median volume was 9207mm3 (IQR 5132, 21710) for the baseline MRIs and 2872mm3 (IQR 1827, 18830) for the post-treatment ones.