Background/Purpose: A combined service evaluation by the rheumatology and radiology department was undertaken to understand the frequency and reporting standards of Computer Tomography-defined Sacroiliitis (CTSI) in patients with Inflammatory Bowel Disease (IBD) imaged for non-musculoskeletal indications.

Methods: CT scans of the abdomen and pelvis were identified retrospectively from the radiology imaging system (RIS) between January 2010 and December 2017. The results were then filtered to ages between 18 to 55 year olds, which is commonly considered to be the population with the highest diagnostic yield for axial spondyloarthritis (axSpA). Only scans of patients with confirmed IBD (Crohn’s disease (CD) or Ulcerative Colitis (UC)) were evaluated. For patients who have undergone multiple scans, the most recent CT scan was used as the index scan. CT scan evaluation was undertaken by 3 radiology trainees (trained and under supervision of a senior musculoskeletal radiologist) in order to identify incidental CTSI, highly suggestive of axSpA ^(1,2).

Results: A total of 301 unique scans of confirmed IBD patients (mean age 36; male 49.2%) were evaluated. The frequency of CTSI using the maximum sensitive criterion of an validated CT screening tool ⁽¹⁾ was 19.9% (60/301). In 53 UC and 248 CD patients, the percentage of CTSI were 17.0% UC (9/53) and 20.6% CD (51/248) respectively. Of the 60 positive scans, 15/60 were reported as sacroiliitis but no reference was made for further rheumatological assessment; of these 15, seven had no previous diagnosis of axSpA. Of the remaining 45 CTSI; 26 were unidentified despite a bone evaluation having apparently been undertaken, 17 did not mention a bone evaluation, 2 were unidentified despite the SI joints having been reviewed.

Conclusion: An estimated 20% of selected IBD patients’ scans have sacroiliitis indicative of possible underlying axSpA diagnosis but these were not reported in 75% of cases. There is a need to raise the awareness of this association and perhaps the utilisation of a validated CT tool may advance reporting excellence. Further assessment of this select group may help differentiate between asymptomatic sacroiliitis and a potential hidden burden of axSpA among IBD patients undergoing CT scanning for non-musculoskeletal indications.

References:

1. Chan J, Sari I, Salonen D, Inman RD, Haroon N. Development of a Screening Tool for the Identification of Sacroiliitis in Computed Tomography Scans of the Abdomen. J Rheumatol 2016;43:1687–1694.
2. Chan J, Sari I, Salonen D, Silverberg MS, Haroon N, Inman RD. Prevalence of Sacroiliitis in Inflammatory Bowel Disease Using a Standardized CT Scoring System. Arthritis Care Res (Hoboken) 2017.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-service-evaluation-of-reporting-standards-of-computer-tomography-defined-sacroiliitis-suggestive-of-axial-spondyloarthritis-in-inflammatory-bowel-disease-patients-imaged-for-non-musculoskeletal-indi/