Post-Bariatric Surgery Inflammatory Arthritis: Clinical Patterns and MRI Characteristics

Introduction: Postoperative inflammatory arthritis, including new-onset spondyloarthritis (SpA), has been increasingly recognized after bariatric surgery, potentially driven by surgery-induced alterations in the gut microbiome. Understanding these postoperative inflammatory patterns is crucial, and this study examines the emergence and characteristics of SpA following bariatric procedures. Material Method: This retrospective study included 14 patients who developed new-onset musculoskeletal symptoms following bariatric surgery between 2010 and 2025. Demographic data, pre- and postoperative BMI, and the interval between surgery and symptom onset were extracted from hospital records. Laboratory assessments included ESR, CRP, ANA, RF, anti-CCP, and HLA-B27. Clinical features such as inflammatory back pain, enthesitis, dactylitis, psoriasis, uveitis, peripheral arthritis, and gastrointestinal symptoms were recorded. Sacroiliac radiographs and MRI scans were reviewed for sacroiliitis, bone marrow edema, structural lesions, and peripheral inflammatory findings. Patients were classified as axial or peripheral SpA according to ASAS criteria, and seronegative patients with imaging-negative arthritis were categorized as undifferentiated arthritis. Results Among 512 bariatric surgery patients, 14 (2.7%) developed new-onset inflammatory arthritis. The mean age was 48.1 ± 12.3 years, and the mean latency from surgery to symptom onset was 56.7 ± 31.6 months. Enthesitis (35.7%), dactylitis (42.9%), and inflammatory low back pain (78.6%) were common. Six patients (42.9%) had axial SpA with MRI-confirmed sacroiliitis, and seven (50%) had peripheral SpA-four with MRI-confirmed peripheral inflammation, one with HLA-B27–associated arthritis, and two with reactive arthritis following infection. One patient (7.1%) had undifferentiated arthritis despite negative serologic, microbiologic, and imaging evaluations. Conclusion New-onset inflammatory arthritis occurred in 2.7% of bariatric surgery patients, most commonly presenting as axial or peripheral SpA. MRI-confirmed sacroiliitis and peripheral inflammatory findings were frequent, and over one-third had enthesitis or dactylitis. Despite substantial postoperative weight loss, a subset developed clinically significant inflammatory disease requiring advanced therapies. These findings suggest bariatric surgery-related immune or microbiome shifts may trigger SpA in predisposed individuals.