Clinical presentation, magnetic resonance imaging characteristics, and short-term outcome of deep surgical site infection following thoracolumbar decompressive spinal surgery for intervertebral disc herniation in dogs

Objective To characterize the clinical presentation, magnetic resonance imaging (MRI) features, and short-term outcomes of deep surgical site infection (SSI) following thoracolumbar (TL) decompressive spinal surgery for intervertebral disc herniation (IVDH) in dogs. Method Retrospective, single-center observational study of dogs that underwent postoperative MRI and were diagnosed with culture-confirmed deep SSI after TL decompressive spinal surgery between 2017 and 2021. Medical records and MRI studies (pre- and postoperative) were reviewed. Results Nineteen dogs were diagnosed with deep SSI among 1723 thoracolumbar decompressive surgeries (incidence: 1.1%). The median time to SSI diagnosis was 7 days (range, 2–38 days). Clinical signs included spinal hyperesthesia (100%) and neurological deterioration (36.8%). MRI revealed bilateral epaxial muscle hyperintensity (66.7%), fascial plane tracking (100%), and multifocal signal voids (89.5%) as possible differentiating features. Staphylococcus spp. were the most common isolates (52.6%). All dogs survived to discharge, with 73.7% being ambulatory; short-term follow-up, available in 14/19 cases, showed resolution of clinical signs. Conclusion and clinical significance Deep SSI after TL spinal decompression typically presents within 2 weeks with spinal hyperesthesia. Several MRI patterns may be associated with SSI. Despite rare complications, the majority of cases had favorable short-term outcomes.