659487.fig.004a
(a)
659487.fig.004b
(b)
Figure 4: A 37-year-old male with 1–3 years duration of inflammatory low back pain. (a) The initial CT shows unilateral sacroiliitis with subtle but definite erosions on the iliac side of the right sacroiliac joint. (b) After 5.5 years, there is progression to bilateral moderately advanced sacroiliitis.