Fig. 1

Computed tomography imaging with contrast, (A) sagittal and (B) axial views. Arrow: a gas-containing, faintly rim-enhancing fluid collection (17 ± 8 Hounsfield unit) at the deep aspect of the right iliacus muscle overlying the right sacroiliac (SI) joint measuring 3.4 × 1.2 × 3.9 cm