Sacroiliitis

Sacroiliitis

HLA-B27 negative serology.

CR – Subtle sclerosis of iliac side of left sacroiliac joint.

MR – Oblique axial FS T1 and FS proton-weighted and oblique coronal FS T2 and postgadolinium FS T1 images of the sacroiliac joints show hypointensity (sclerosis) of the left sacroiliac joint and T2 and postgadolinium T1 hyperintensity and articular irregularity of the right sacroiliac joint.

Symptoms of sacroiliitis are indistinguishable from most other etiologies of low back pain. Differential considerations of sacroiliitis include ankylosing spondylitis, psoriatic arthritis, Reiter syndrome; unilateral disease may be seen with gout, rheumatoid arthriits, enteropathic arthropathy and pyogenic arthritis.

MR is the preferred diagnostic imaging test for sacroiliitis. On MR, the most characteristic feature of sacroiliitis is loss of the intermediate T1 signal and increase in T2 signal of the caartilage related to inflammation. Irregularity of the cortices with high signal extending to the marrow, erosions along the anteroinferior synovial compartment (most pronounced on the iliac side of the joint), and high signal in the joint (inflammatory fluid and pannus) are also seen.

Radiography is often employed early in the workup of low back pain although findings are usually subtle and nonspecific. Scintigraphy and computed tomography should be used sparingly because of radiation exposure.

Murphey MD, et al. Sacroiliitis: MR imaging findings. Radiology (1991); 180:239-244.