Are We Overcalling Sacroillitis on MRI? Differential diagnosis that every rheumatologist should know - Part II.

In the second part of this review article we will describe the imaging features of non- spondyloarthritis (SpA) pathologies that may mimic sacroiliitis on Magnetic Resonance Imaging (MRI), and that readers should be aware (part 2). Based on the established literature, there is currently an "overcall" of sacroiliitis on MRIs. In this setting, differential diagnoses and their imaging features come into play. In fact, non-SpA related sacroiliac joints (SIJs) pathologies are more commonly found than true sacroiliitis on MRI of the SIJs, even in patients with inflammatory type back pain. An imaging literature review, highlighting "easy-to-use" learning points regarding MRI interpretations in patients with suspected sacroiliitis and/or nonspecific lumbar back pain is presented. This two-part article aims to be a snapshot of the most common inflammatory versus non-inflammatory entities found on SIJs imaging studies in routine practice, while trying to keep this review article simple, educational and above all, practical.