Study compares CT, ultrasound, and histology in equine SI region

A comparative imaging study in Animals is adding nuance to how veterinarians assess the equine sacroiliac and lumbosacral region. Researchers from the University of Zurich evaluated multidetector helical CT, transrectal ultrasonography, and histology in adult Warmblood horse cadavers, asking a practical question for clinicians: how often do structural abnormalities appear in horses without recognized clinical signs? Their findings suggest the answer is, quite often. (pubmed.ncbi.nlm.nih.gov)

That question matters because sacroiliac and lower back pain are well-recognized contributors to poor performance, stiffness, and hindlimb gait abnormalities in sport horses, yet the region is difficult to assess. Prior reviews and educational materials describe transrectal ultrasonography as a routine tool for evaluating the ventral caudal lumbar, lumbosacral, and sacroiliac area, while also noting the importance of careful anatomical knowledge and clinical correlation. Advanced imaging, including CT, has expanded what clinicians can visualize, but access, cost, and interpretation remain limiting factors in equine practice. (ivis.org)

In the new study, the authors reported on 15 adult Warmblood cadavers, representing 25 sacroiliac joints, from horses euthanized or slaughtered for reasons unrelated to the project between September 2021 and May 2023. The horses were 5 to 18 years old, with a mean age of 12.3 years, and had reportedly shown no clinical signs of sacroiliac disease before death. According to the publication record, the study’s objective was to describe, grade, and correlate CT, transrectal ultrasonographic, and histologic findings in this population. (pubmed.ncbi.nlm.nih.gov)

The central finding was that imaging and histopathologic changes were common despite the lack of known clinical signs. The paper’s abstracted summary indicates the authors saw value in CT for detailed assessment of the region and concluded that imaging findings should be interpreted alongside histopathology and clinical presentation, rather than in isolation. That fits with related post-mortem work showing that anatomical variation and acquired bony changes in the lumbosacroiliac region can be detected on both CT and ultrasound, even outside a straightforward clinical disease picture. (mdpi.com)

I did not find a separate institutional press release or a formal outside expert commentary tied specifically to this paper. Still, the broader equine imaging literature points in the same direction: ultrasound is useful and practical for the ventral lower back and sacroiliac region, while CT can reveal additional structural detail that may sharpen an anatomic diagnosis. Reviews also caution that imaging alone rarely settles whether a lesion is clinically important, especially in complex back-pain cases. That’s an inference drawn from the surrounding literature, not a direct quote from an outside commentator. (ivis.org)

Why it matters: For veterinary professionals, especially equine practitioners and imaging specialists, this study reinforces a familiar but important message: abnormal images don’t automatically equal clinically meaningful disease. In referral settings, where CT may be available, the data support its role as a complementary modality for characterizing the sacroiliac and lumbosacral region. In field and ambulatory practice, the findings also support continued use of transrectal ultrasonography, while underscoring the need to interpret those findings in the context of performance history, palpation, gait assessment, neurologic examination, and other diagnostics. (pmc.ncbi.nlm.nih.gov)

The study may also help temper expectations in conversations with pet parents of performance horses. If structural changes are common in horses without recognized signs, then a positive imaging finding may be only one piece of the puzzle, not the answer by itself. That has implications for case workups, treatment selection, and how veterinarians explain uncertainty around prognosis and return-to-work decisions. (pmc.ncbi.nlm.nih.gov)

What to watch: The next meaningful development will be prospective work in live horses that links CT and ultrasound findings with pain localization, clinical outcomes, and response to treatment, helping clinicians distinguish incidental change from actionable pathology. (pmc.ncbi.nlm.nih.gov)