Contrast-enhanced MRI can demonstrate active inflammatory changes of the sacroiliac joints and spine in axSpA, although multiple studies show that noncontrast and contrast-enhanced MRI have overall similar diagnostic utility for axSpA [9,107-111,125-129]. Contrast-enhanced MRI has been reported to increase the diagnostic confidence and reliability of MRI interpretation in 2 studies [9,107]. US Sacroiliac Joints US is not suggested as a routine diagnostic modality for the evaluation of sacroiliitis in patients with suspected axSpA because of its lack of established diagnostic utility [22]. Importantly, US provides evaluation limited to the superficial posterior margins of the sacroiliac joints, and therefore many structural details are not demonstrated. Many of the available studies examine the utility of Doppler evaluation. It has been shown that patients with active sacroiliitis because of axSpA have lower Doppler US resistive indices than healthy controls or patients with osteoarthritis at the sacroiliac joints [130-132]. Using MRI as the reference standard in a study of 51 patients with AS, a pulsatile monophasic waveform was shown to have a sensitivity of 82% and specificity of 92% for active disease, although 18.5% of active AS patients, 70.8% of inactive AS patients, and 63.3% of normal patients had no Doppler flow identified, and the sensitivity for detection of AS patients overall was only 43% [133]. One study reported higher sensitivity of contrast-enhanced US compared with conventional US [134,135]. A recent systematic review of US of the sacroiliac joints in spondyloarthritis reported a median sensitivity of 90% and specificity of 89% in seven of those studies, although with variation in the method of evaluation and reference standard. The authors concluded that there is not enough evidence to support the use of US for the diagnosis of axSpA [136].
Inflammatory Back Pain Known or Suspected Axial Spondyloarthropathy PCAs. Contrast-enhanced MRI can demonstrate active inflammatory changes of the sacroiliac joints and spine in axSpA, although multiple studies show that noncontrast and contrast-enhanced MRI have overall similar diagnostic utility for axSpA [9,107-111,125-129]. Contrast-enhanced MRI has been reported to increase the diagnostic confidence and reliability of MRI interpretation in 2 studies [9,107]. US Sacroiliac Joints US is not suggested as a routine diagnostic modality for the evaluation of sacroiliitis in patients with suspected axSpA because of its lack of established diagnostic utility [22]. Importantly, US provides evaluation limited to the superficial posterior margins of the sacroiliac joints, and therefore many structural details are not demonstrated. Many of the available studies examine the utility of Doppler evaluation. It has been shown that patients with active sacroiliitis because of axSpA have lower Doppler US resistive indices than healthy controls or patients with osteoarthritis at the sacroiliac joints [130-132]. Using MRI as the reference standard in a study of 51 patients with AS, a pulsatile monophasic waveform was shown to have a sensitivity of 82% and specificity of 92% for active disease, although 18.5% of active AS patients, 70.8% of inactive AS patients, and 63.3% of normal patients had no Doppler flow identified, and the sensitivity for detection of AS patients overall was only 43% [133]. One study reported higher sensitivity of contrast-enhanced US compared with conventional US [134,135]. A recent systematic review of US of the sacroiliac joints in spondyloarthritis reported a median sensitivity of 90% and specificity of 89% in seven of those studies, although with variation in the method of evaluation and reference standard. The authors concluded that there is not enough evidence to support the use of US for the diagnosis of axSpA [136].