What Diagnostic Imaging Reveals About a Horse
Diagnostic imaging results are clearer than ever, but how they will affect a horse’s performance career isn’t always as evident
Veterinarians have been using diagnostic imaging to assess horses for decades. Being able to visualize healthy structures—as well as fractures, soft tissue tears, and more—using radiographs and ultrasound has long allowed practitioners to diagnose lameness and gauge performance potential. While the images weren’t always the clearest or easiest to evaluate in the early days, vets did their best with the information they had.
Today it’s a different story. Traditional imaging options have improved, allowing veterinarians to see injuries or other anomalies they never knew existed years ago, and advanced modalities are providing more detailed looks at horses’ anatomical structures than ever.
“Of course, with more advanced imaging, the vet has the potential to see more incidental findings,” says Kirstin Bubeck, DrMedVet, Dipl. ACVS, ACVSMR, a clinical assistant professor of large animal surgery and sports medicine at Tufts University Cummings School of Veterinary Medicine, in North Grafton, Massachusetts.
We know not every imaging abnormality causes lameness or reduces performance potential. So which ones are bad news, and which ones don’t matter?
Spoiler alert: All imaging findings matter. The question is which findings are clinically significant in a particular horse and which ones are likely to have little impact on a performance career. The answer is anything but simple.
Improving Technology, More Information, More Challenges
Advancements in imaging technology mean veterinarians no longer must bring X ray films back to the clinic to evaluate. They’re not bound by static endoscopy to evaluate airway issues that arise during exercise. And they’re not limited to fuzzy and difficult-to-interpret ultrasound images. Portable digital radiograph machines now let veterinarians see inside a horse almost instantly and enhance or adjust images to make defects easier to identify and assess. Ultrasound images reveal more detail, and endoscopes can show what’s going on in a horse’s throat as he gallops around a track. Veterinarians even have access to more advanced imaging technology that has opened new diagnostic doors.
“Advanced imaging modalities, such as MRI, CT scans, nuclear scintigraphy, and PET scan, have the advantage of providing complementary information to that provided by radiography and ultrasonography,” says Alison Morton, DVM, MSpVM, Dipl. ACVS, ACVSMR, a clinical associate professor, chief of large animal surgery, and large animal hospital medical director at the University of Florida College of Veterinary Medicine, in Gainesville.
Each advanced modality provides different information (which you can learn more about at TheHorse.com/1104231), she says, which can help give veterinarians a more complete picture of an issue and help them determine whether an abnormality is clinically significant.
“Some abnormalities are obvious standalone lesions that may not require additional imaging, but for lesions that are less obvious, less common, or when there are multiple abnormalities that may or may not be contributing to an issue, use of complementary imaging is recommended,” she adds. “Advanced imaging should help to sort out significance of findings (or lack of findings) on baseline images and help us to learn how to better interpret radiographic and ultrasonographic findings.”
The ability to visualize more abnormalities in better detail does, indeed, improve diagnostic capabilities. But in some cases it can also present challenges.
“Determining the potential impact of imaging findings on performance is challenging for several reasons,” says Morton. “Firstly, we do not have enough evidence-based information to make definitive decisions regarding many of the changes we may find on various images. Secondly, for many of the conditions we do have information regarding, we find that imaging findings may not correlate with clinical findings—a horse may have changes on a radiograph or other type of image, but that horse is not exhibiting lameness or any problems with performance (for instance, anomalies might be caught during a screening exam on a sound horse such as a prepurchase). Thirdly, evaluation of images is only a snapshot of one aspect of the horse at a given moment. That snapshot lacks perspective on that horse’s history and exam, which are equally or may be more important than that isolated piece of information.”
Myra Barrett, DVM, Dipl. ACVR, ACVR-EDI, an associate professor of veterinary diagnostic imaging at Colorado State University’s College of Veterinary Medicine & Biomedical Sciences and a partner at Inside Information Radiology, both in Fort Collins, agrees. Certain abnormalities can impact horses working in various disciplines differently, she says. Then there’s individuality: “There’s just so much variability in horses,” she says. “They don’t all respond the same way” to injuries, diseases, and imaging abnormalities, and the same abnormality in two horses can have significantly different clinical implications from a risk standpoint.
“If you have a 14-year-old Warmblood who’s in full work, at the level at which you want them to work, and they’re pretty sound, then a lot of radiographic or other imaging findings you might find on a screening study may be less concerning,” Barrett says.
The same findings in a 3-year-old prospect who’s not yet in training, however, could significantly and negatively impact that horse’s future athletic potential. “Then it’s really like trying to read a crystal ball,” she says. “You’re making your best guess on how they’ll be affected based on a bunch of other horses who’ve come before.”
Imaging Doesn’t Help in a Vacuum
“When I give talks on radiographic significance, I have an analogy,” Barrett says, which she bases both on her experience and what other researchers have found and documented. “First I have my red box, and in the red box are bad things. Rarely are these findings incidental. Rarely do they not cause a problem.”
Then she has her “incidental box.” These findings might not be normal on radiographs but, in her experience, don’t often cause significant clinical issues, she says.
“And then, unfortunately, the rest—which are most of the findings—fall into a gray zone box,” she says. They could go either way.
“Imaging is really important, but it’s only a piece of the puzzle, and it doesn’t really help you in a vacuum,” she says. “You have to have more information to determine what’s significant and what’s not.”
Our sources agree it’s crucial to consider as many additional factors as possible—such as the horse’s history, purpose (Is he a resale prospect or a forever horse?), current soundness, and clinical exam findings—when considering what impact lesions could have.
For instance, if a horse is lame, chances are he’s already been through clinical exams to identify the area to be imaged. Still, multiple flaws and even artifacts (misrepresentations of tissue structures produced by imaging techniques) can appear on images.
“Different nerve or joint blocks can help differentiate between a more important or less important lesion,” Bubeck says. “Or there can be chronic changes which may be less important in a horse which has performed at the desired level successfully, while acute changes present at the same time will be more important.”
Consider radiographic findings from a prepurchase on a sound horse, for example: “Say the purpose of a horse is to belong to a junior rider while she’s in high school and (be sold) when she goes to college,” Barrett says. “It has something abnormal on the radiograph, but I don’t think it’s going to be that significant clinically. That could still be a problem for resale because some people just won’t buy horses that have radiographic blemishes.
“Then there’s the case where an owner says, ‘This is the horse I want forever. I don’t care about resale.’ If, say, the horse has hock arthritis, you can say, ‘Okay. Well, this is something we might have to manage a little bit, but it’s probably not going to be a big deal. You’re not going to be trying to sell this horse, so don’t worry too much about it.’ ”
Bubeck agrees: “While there are some joints which do not tolerate (arthritic) change well, there are certain findings in many other joints which are known to be normal variations and not cause problems. Not every horse that has signs of mild osteoarthritis, for example, will show problems. We have to still mention this to the potential buyer since it potentially can get worse, and they will have to assess their willingness to take risks.”
Even with the best history and clinical exam possible, it can still be challenging to determine which findings are likely to impact a horse’s career. In these cases Morton encourages veterinarians to consult with colleagues who specialize in and have copious experience evaluating images and exam findings. These individuals can recommend the diagnostic imaging modalities that could provide the best results and can interpret the images following examination.
Imaging Findings, the Horse, and the Owner
Regardless of whether a horse is sound or lame, it can be concerning for an owner to see potential bone or other tissue problems on a screen, especially issues they haven’t encountered before. It can then be confusing to hear that the blemishes might not affect the horse’s future. In these cases it’s all about communication between veterinarian and owner.
“As a huge imaging fan,” says Morton, “I think information is knowledge, but it does not dictate our future. I remind my owners that we need to look at the whole horse and that not many of us are perfect: ‘Most horses have some abnormalities, and this is an abnormality that I consider low-risk.’ I tell them baseline imaging provides us information that we can monitor throughout a horse’s career and, coupled with routine and diligent examinations, may provide insight on developing problems and allow changes in training programs to prevent performance problems.”
Routine imaging and exams can even help in resale situations, she says. For example, “if a potential purchaser has a prepurchase exam performed, you have the historical images for comparison, along with the horse’s performance history.”
If the horse has had a particular flaw on his images since Day 1, and it’s had no impact on his performance, it could convince a purchaser and their veterinarian the finding is a blemish unlikely to impact performance, at least at the current level. Conversely, without past images, that blemish could negatively impact the sale price or transaction.
Barrett agrees it’s all about explaining to an owner that just because something doesn’t look right doesn’t mean it’s going to cause a problem. Sometimes veterinarians just need to explain their findings in an understandable and relatable way.
“Let’s say you have a crack in the plaster over the drywall in your house,” Barrett says “That’s not necessarily a structural problem. It doesn’t make your house less safe. It doesn’t necessarily cause leaks. It doesn’t do anything other than not look very pretty.”
All imaging findings matter. The key is determining whether a finding will have a negative impact on a horse’s athletic career. This remains a challenge and depends on the horse’s history and use.
“Abnormalities are abnormalities, they just may or may not be important,” Morton says. “That is the tough thing to sort out, especially on a single day or one snapshot in time. It would be nice to be able to predict the potential outcome of an abnormality that is not causing a current problem from a single point in time, but we would truly need a crystal ball to provide those answers.”
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