Figure 2: MRI of the pelvis and sacroiliac joints. Coronal T1-weighted (a) as well as (b) fat-saturated (FS) post IV contrast images of the pelvis and sacroiliac joints; showing a 5 cm in diameter multiloculated collection showing dense marginal enhancement deep to left iliopsoas muscle communicating with underlying left sacroiliac joint cavity (see arrow) with evidence of left sacroiliitis in the form of irregular articular surface with subarticular thickening as well as enhancement.