[Sacroiliitis or pseudosacroiliitis?]

When the presence of seronegative spondyloarthropathy is unrecognized there can be a delay in achieving an accurate diagnosis, as the typical inflammatory low back pain is similar to that found in degenerative diseases of the lumbosacral spine and the sacroiliac joints. Thus, seronegative spondyloarthropathy is often misinterpreted as a degenerative disease. The initial radiography of the sacroiliac joints is often normal which results in a delay in diagnosis of sacroiliitis of approximately 3-7 years.

This illustrates the significance of an adequate imaging method for the early detection of sacroliliitis.

Contrast medium administration for magnetic resonance imaging (MRI) enables a differentiation between synovitis, capsulitis, enthesitis and effusion.

Sensitivity and specificity for detection of active inflammation by MRI is about 83-85%. Early active inflammation can be detected by MRI 3-7 years before structural changes are obvious by x-ray examination.

Pseudosacroiliitis can be differentiated from inflammatory sacroiliitis by the patient history, laboratory data, osteoproliferative and osteodestructive changes and the typical distribution pattern of bone marrow edema.