Perianal fistuala in Crohn disease | Figure 1

CincyKidsRad
Cincinnati Children's Radiology

Perianal fistula in Crohn disease

Axial T2 weighted MRI (images 1-3) in an adolescent with Crohn's disease shows a perianal fistula (arrowhead) arising from the 6 o'clock position. Edema tracks to the right and left gluteal crease with a more focal collection (arrow) on the left buttock. Crohn disease is an inflammatory bowel disease associated by transmural inflammation. Perianal fistulas can be difficult to identify on enterography. Dedicated small field-of-view imaging of the pelvis should be performed. Perianal fistulas appear as fine linear tracts best seen on T2 weighted images. It can be associated with subcutaneous abscesses. An abscess is better diagnosed with postcontrast images showing a small area that does not enhance. The edema and perianal inflammation (arrow) is highlighted on the coronal T2 weighted image (image 4). Sacroiliitis (dashed arrow), a potential extraintestinal manifestation of Crohn's disease is also present.