Evaluation of complex appearance in vascularity of sacroiliac joint in ankylosing spondylitis by color Doppler ultrasonography.

To investigate the complex appearance of vascularity of sacroiliac joint (SIJ) in ankylosing spondylitis. Sixty-eight patients and 35 controls were included in the study. Blood flow was examined at the SIJ by using color Doppler ultrasonography (CDUS). The location of color flow signs and flow pattern were observed. Arteries do not present reversed phase in diastolic phase on pulse Doppler sonography, and if they were found inside and around the SIJ, the resistive index (RI) was measured. In active AS patients, the region of SIJ presented increased vascularization greater than those in inactive AS (P = 0.001) and the controls (P = 0.001). There are three different spectral Doppler tracings: arterial flow (RI < 1), arterial flow representing reversed phase in diastolic phase on spectral Doppler sonography and venous flow. Besides arterial flow signs, most of color flow signs presented venous flow in active AS. Significant increases in a number of venous flow signs in active AS cases (P < 0.001) were observed. In most cases, two or more different flow patterns presented in a region very close to the location of SIJ. In addition, a different vascularization was observed. Abnormal vascularization at the sacroiliac joints can be detected by CDUS. The vascularization in SIJ presented complex appearance, which increases the difficulties of CDUS examination. Venous blood flow in the assessment of active AS merits further study.