This is something I hear all the time….. and no my answer is not going to be get out a sports therapist! Usually the way this occurs is the client calls the therapist because the horse isn’t right and the therapist can’t pin point the issue so recommends the vet and the vet gets stumped because the horse doesn’t change with flexion tests or nerve blocks. Often it might be a performance issue or a subtle lameness. So what next?
Commonly a vet would move to radiography or ultrasonography which is great if you know where you’re heading in terms of region, but as an owner I find there is a lot of confusion around what the differences between these two are (in terms of what they diagnose not the bleeding obvious) and also what other options are out there and what they mean. for example did you know that we had a full body MRI in WA? Nope, neither did I but I had someone with a pelvic issue tell me they were booking the horse in for an MRI…. this is the kind of confusion that we get met with.
Really the best thing is for your vet to refer you to a diagnostic centre, but if your vet is associated with a centre themselves that has a piece of equipment, are they going to send their money elsewhere and refer you to a different centre for a more appropriate scan? I guess it depends on the vet…
What I’m hoping this little blog will do will just give you a brief outline of what each of the diagnostics means to arm you with a bit of knowledge to understand what your vet is saying a bit better! But you also need to bear in mind when reading this that if you have a horse in this situation then you need a vet on board for the whole process. Because they are indicators not miracles. Lets say your horse goes in for a scan and it highlights issues in the cervical neck. You will then possibly need further diagnostics to determine what the actual issue is but also a management plan moving forward. It takes a village to raise a child.
So what do all these big words mean!!
Radiography (X-Ray) – This is probably the most commonly used diagnostic tool and the most familiar to everyone. Radiographs generate pictures of bones by passing a radioactive beam through the patient to project an image on an imaging plate. X-rays are very commonly used in diagnosing hoof issues as they can see inside the hoof capsule. Generally, radiographs are ideal for diagnosing bone problems, while ultrasound is better for discovering tendon and ligament injuries. “But you can also sometimes see some remodeling on the bone itself where the ligament attaches.” X-rays are not helpful in areas such as the lower back or pelvis where the width the beam needs to travel is too far.
Ultrasound – Although we often think of this for use in reproductive medicine, ultrasound is also very effective at diagnosing soft tissue issues. Diagnostic ultrasound uses high frequency sound to create a map of soft tissue in the body. Ultrasound waves travel through and “echo” back to the transducer from different tissue densities. The transducer collects the waves that bounce back and a computer then uses those sound waves to create a picture giving detailed real-time images of a wide range of anatomical structures. Bone, which is dense, is identified on screen as a bright white line, whereas a tendon appears as shades of grey and fluid is black. Although ultrasound cannot be used to examine the deeper structures in bone as bone matter is too dense it can be used to investigate problems of bones in areas where obtaining good quality x-rays is problematic, such as the pelvis and spine. We can also use it to assess bone margins and to look at the attachment of soft tissues to bone or changes on the surface of the bone. This test is an operator-dependent diagnostic test. In humans we have specialised ultrasonographers trained to read ultrasounds, but in Australia this is done by our vets. Some of which find it easier then others. An ultrasound is completely non invasive and often doesn’t even require sedation.
Scintigraphy – (Nuclear medicine, nuclear scanning, bone scanning) is an established modality in medical imaging that provides very sensitive diagnostic information that cannot be obtained by other techniques such as x-rays, computed tomography, magnetic resonance and ultrasound. Scintigraphy provides us with a screening tool to locate areas of increased metabolic activity in bone which may indicate a site of injury. Nuclear imaging requires the administration of a short-lived radionuclide tracers which emit gamma rays. A nuclear scanner is used to detect the gamma rays creating detail of both the structure and physiological function of the underlying anatomy being studied.
The horse is injected with a radioisotope which is absorbed in increased amounts in regions of the body undergoing remodelling processes. Remodelling can indicate a source of pathology. Using a special gamma camera, any areas of increased uptake can be identified. Once an area is identified, further diagnostic techniques are used to ascertain the significance of the findings.
Scintigraphy or bone scanning is particularly useful for imaging areas that are difficult to x-ray such as the pelvis, back and upper limbs as well as isolating problems that might not be readily apparent on x-rays, such as stress fractures. It can also be used to detect early bony changes before they become visible on radiographs and can be a useful tool in poor performance work ups or multi-limb lamenesses, where there may be several sites of pain.
Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are nuclear medicine imaging techniques which provide metabolic and functional information unlike CT and MRI. The difference between the two is the radioactive isotope used. In WA we are lucky enough to have the only 3D Pelvic SPECT form of nuclear medicine at TelemedVET with limb scintigraphy available elsewhere. General anaesthesia is not required and it is a non invasive procedure. A PET scan is another form of nuclear medicine
MRI – MRI is an imaging test that uses a magnetic field and pulses of radiofrequency energy to make an image of structures in the patient, usually distal limbs. MRI is suitable for specific investigation of musculoskeletal injury, including bone oedema, ligamentous and tendon injury. In WA we have the ability to MRI structures of the leg. This is a standing procedure that doesn’t involve anaesthesia.
Image source: https://hallmarq.net/us/products-services/standing-equine-mri/
CT Scan (Computed Tomography) – CT produces information, using X-rays projected from different angles around the patient, which is then processed to produce cross-sectional images. This produces an entire 3D image of the horses head. In horses, CT imaging is particularly useful for investigating diseases of the head, including dental abnormalities, sinus and nasal passage problems, traumatic injuries of the skull, headshaking and neurological diseases. There are several advantages of CT compared to conventional two-dimensional x-rays. In a CT scan adjacent structures are not superimposed on top of each other as they are in an x-ray making them much easier to isolate. Some clinics may also CT a distal limb but this requires general anaesthesia. In WA we are lucky enough to have a CT scan at Murdoch equine.
Image source: https://www.bwequinevets.co.uk/17/Expert-Horse-CT-Computed-Tomography-Scan/
I will leave you with these short succinct words from Dr Kent Allen from Virginia Equine Imaging “Absent a diagnosis, medicine is poison, surgery is trauma, and regenerative medicine is witchcraft,”
Sources:
- https://www.kilmoreequine.com.au/
- https://www.imv-imaging.com/international/veterinary-learning/equine-learning
- https://www.bwequinevets.co.uk/
- https://www.telemedvet.net/
- https://thehorse.com/138866/in-depth-understanding-radiographs-x-rays/
- https://vaequine.com/
