Computed tomography in axial spondyloarthritis

Purpose of review Computed tomography (CT) is increasingly being used in ankylosing spondylitis (AS) for imaging the spine and sacroiliac joint (SIJ). We review new insights to diagnosis and evaluation revealed by the use of CT. Recent findings Studies using low-dose CT in AS to detect syndesmophytes can image the entire spine, but semiquantitative scoring of the scans by human readers decreases the reliability and validity of this method. The thoracic spine is the segment most involved with syndesmophytes. Syndesmophytes are not randomly distributed around the vertebral rim but have preferred locations, which vary with the vertebral level and may be related to biomechanics. Examination of SIJ on abdominal CT scans has found structural changes of sacroiliitis in up to 35% of patients with inflammatory bowel disease. The significance of monosodium urate crystal deposition in the pelvis of axial spondyloarthritis patients without coexisting gout is uncertain. Summary Low-dose CT is a promising tool in AS. Studies of biomarkers or medications and their relations with syndesmophyte progression should take the thoracic spine into account. Abdominal CT scans are useful for detecting changes related to sacroiliitis.