Scanning of the Sacroiliac Joint and Entheses by Color Doppler Ultrasonography in Patients with Ankylosing Spondylitis

Objective. To assess Doppler ultrasonography by comparing its detection of sacroiliitis with detection of enthesitis in patients with ankylosing spondylitis (AS). Methods. One hundred sixty-one patients with AS (according to modified New York criteria or Spondyloarthritis International Society classification criteria for axial spondyloarthritis) underwent ultrasonography (US) of the sacroiliac joint (SIJ) and major entheses of the lower limbs. Vascularization of the SIJ and morphologic changes and vascularization of entheses were observed. The resistive index of the SIJ was measured. Doppler ultrasonography examination was repeated in 20 patients by another ultrasonographer. Results. In the AS active group [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) >= 4] 90.7% of SIJ showed vascularization; this was significantly more than in the inactive group (38.5%). The resistive index of the active group in the SIJ area was significantly lower than that of the inactive group. Doppler US scanning of the SIJ was more sensitive (92.0%) than that of the entheses (52.2%). Agreement of Doppler US scanning of the SIJ and BASDAI was good, while agreement of the entheses and BASDAI was poor. Conclusion. Lower resistive index value and vascularization in the SIJ had good agreement with AS activity. Doppler US is more sensitive in detecting sacroiliitis than in detecting enthesitis. (First Release May 152011; J Rheumatol 2011;38:1651-5; doi :10.3899/jrheum.101366)