The prevalence of sacroiliac joint CT and MRI findings is high in large breed dogs.

Sacroiliac joint (SIJ) disease has been described as one of the possible causes of lumbosacral (LS) region pain in dogs. However, published information is currently lacking for the computed tomographic (CT) and magnetic resonance imaging (MRI) characteristics of canine SIJ disease. The objectives of this retrospective, observational study were to describe and quantify CT and MRI SIJ findings in a sample of large breed dogs and test associations between the numbers of SIJ findings and other variables. Data archives for a veterinary teaching hospital were searched for large breed dogs (≥ 22.7 kg) that had CT or MRI scans of the LS and pelvic regions in 2015-2019. Dogs with a history of acute trauma or scans with incomplete SIJs were excluded. A veterinary student recorded medical record findings. A veterinary radiologist and graduate student recorded CT and MRI findings based on previously published criteria in dogs and humans. Fifty-three dogs were sampled (20 CT, 33 MRI). Categories of findings with the highest prevalence were subchondral erosion (100% CT, 100% MRI) and subchondral sclerosis (95% CT, 97% MRI). The total numbers of SIJ findings per dog were not associated with dog age, sex, weight, or concurrent findings in the LS or pelvic regions. The total number of MRI SIJ findings per dog differed between German Shepherds and Labrador Retrievers (P = 0.0237) as well as between Labrador Retrievers and other breeds (P = 0.0414). These results indicated that CT and MRI findings reported in humans with SIJ disease are common in large breed dogs.