P314 MRI fistulography

Abstract Background Perianal Crohn’s fistulas are often complex and recurrence is common. It is important to reduce recurrence rates as each surgical intervention, and each septic episode leads to further tissue destruction and anatomical distortion. This makes subsequent procedures more challenging and thus recognition and treatment of each extension is paramount. We describe the innovative technique of MRI fistulography to better understand appreciate complex fistula and the extensions. Methods Standard axial T2-weighted Spectral Attenuated Inversion Recovery (SPAIR) MRI sequences were acquired. Digital imaging and communications in medicine (DICOM) images of the MRI sequences were retrieved from the picture archiving and communication system (PACS) system. DICOM images were imported on validated open-source segmentation software. A specialist consultant gastrointestinal radiologist performed segmentation of the fistula tract, the internal and the external sphincter. Each mesh was imported into MeshLab V1.3.3.1 as a Stereolithography (STL) file for surface smoothing to be applied. An animation was created by in collaboration with Touch Surgery™. Results An animated 3D reconstruction of a trans-sphincteric fistula tract with a cephalad extension in the intersphincteric space is demonstrated by a series of screenshots in Figure 1. The animation is orientated as the patient would be in the lithotomy position. The various anatomical components are displayed in different colours (Red: Fistula Tract; Green: External Anal Sphincter (EAS) and Levator Plate; Blue: Internal Anal Sphincter (IAS) and Rectum). The animation is annotated to describe where the tract pierces the sphincter. MRI Fistulography depicted using screenshots for a trans-sphincteric fistula with a cephalad extension in the intersphincteric space Conclusions 3D modelling in the form of MRI fistulography would provide a “road-map” for the complex and more challenging fistulas regardless of their size and angulation. In addition to guiding surgery, it may in some cases prove useful for MDT discussions of complex cases and for “surgical rehearsal.”