ARRS 2022 Abstracts

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E1802. Sacroiliitis: Imaging Diagnosis and Mimics
Authors
  1. Raheem Habib; Baylor Scott & White Medical Center - Temple
  2. Christopher O'Sullivan; Baylor Scott & White Medical Center - Temple
  3. Connie So; Baylor Scott & White Medical Center - Temple
  4. Ricardo Garza-Gongora; Baylor Scott & White Medical Center - Temple
  5. Krista Birkemeier; Baylor Scott & White Medical Center - Temple
  6. Harold Sonnier; Baylor Scott & White Medical Center - Temple
Background
Low back pain is a common presenting complaint resulting in numerous imaging studies. A common source of this pain arises from the sacroiliac joint, which bears the integral role of transferring weight between the axial and lower appendicular skeletons. The ability to recognize and differentiate various sacroiliac joint pathologies is crucial for patient care. This exhibit reviews the imaging characteristics of infectious sacroiliitis, inflammatory sacroiliitis, and their potential mimics as these entities may pose a diagnostic challenge in differentiating from one another.

Educational Goals / Teaching Points
This educational exhibit will begin by illustrating the complex anatomy of the sacroiliac joint and its surrounding soft tissue structures. Next, the utility of radiographs, CT, and MRI will be discussed in the work-up of sacroiliitis. Subsequently, characteristics of infectious sacroiliitis and inflammatory sacroiliitis will be compared on imaging. Potential mimics of sacroiliitis will also be differentiated.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Anatomy of the sacroiliac joint will be reviewed to discuss 1) synovial and ligamentous portions of the sacroiliac joint; 2) bone landmarks; and 3) surrounding soft tissues and ligaments. Knowledge of joint anatomy can aid with identification of pathology as certain diseases affect different parts of the joint and bone. Pathology of the sacroiliac joint may be a result of an infectious sacroiliitis, inflammatory sacroiliitis, or other mimics. Infectious sacroiliitis may present with diagnostic characteristics on imaging that are important to recognize given the clinical implications. Inflammatory sacroiliitis, which encompasses rheumatoid arthritis and seronegative spondyloarthropathies, manifests with acute and chronic features on imaging. Potential mimics of sacroiliitis include osteoarthritis, diffuse idiopathic skeletal hyperostosis, stress fractures, and metabolic bone disease. The various pathologies of the sacroiliac joint will be depicted through radiographs, CT, and MRI in this image-rich exhibit.

Conclusion
Given the prevalence of low back pain, the sacroiliac joint is commonly imaged. The ability to distinguish between the various pathologies of infectious sacroiliitis, inflammatory sacroiliitis, and potential mimics is vital for patient care. A solid foundation of knowledge in anatomy and imaging characteristics helps ensure patients are correctly diagnosed and treated. This educational exhibit aims to enrich this foundation and provides a guide when faced with diagnostic challenges.