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Diagnostics

About diagnosis

There is no doubt that it helps to know exactly what you are treating. It tells you where treatment should be directed and to some degree provides a prognostic indicator as to the likelihood of achieving a successful result and recovery back to normal function. 

There is however, in Roger's opinion and experience, a significant difference between diagnosing the root cause of a problem and simply identifying the presenting symptoms. In many cases what is commonly referred to as a diagnosis, is simply the observed predominant symptom in its Latin translation! Anything that ends in -itis means inflammation, so arthritis is joint inflammation, pneumonia is inflammation of the lungs, hepatitis is inflammation of the liver etc. It sounds more fancy/serious when the Latin name is used, but it doesn't tell you what has caused the inflammation.

When Roger was training to be a vet he was taught to take a clinical history and do a physical examination in order to create a starting differential diagnosis list.  If the treatment for everything on the list was the same, there was nothing to stop that treatment going ahead without any further narrowing down of the diagnosis to anything more specific.  If however there were multiple treatment options that required a more specific diagnosis on order to choose the most appropriate treatment, then and only then, should further tests be undertaken as necessary, and the minimum number of tests performed in order to arrive at the correct treatment option. Tests might include blood tests for medical conditions, or for lameness it might be nerve blocks or some sort of imaging technique. Given that many diseases and lamenesses don't necessarily present as classically described in textbooks, doing every test under the sun prior to constructing a differential diagnosis has great capacity to cause confusion. This can result in a much longer list of possible differential diagnoses than is likely possible, and in some cases a diagnosis that isn't credible. Common things occur commonly .... 

When it comes to imaging you don't need a sledgehammer to crack a nut, and the minimum number of images should be taken using the least harmful type of imaging modality possible. All electromagnetic imaging techniques have the potential to do harm to varing degrees. Just because an X-ray or scintigraphy is used for medical purposes doesn't make it safe. The electromagnetic radiation dose is cumulative, so the number of exposures matters. Roger is extremely concerned that the number of X-rays taken of limbs for a 5 star vetting can reach ridiculously high numbers with seemingly no consideration of what such cumulative exposure is doing to the adjacent bone marrow and the blood that circulates past whilst the images are taken. 

Having a diagnosis doesn't actually progress recovery in itself, and won't necessarily tell you why an injury or illness has occurred either. If a specific accident has been observed, or an injury is obviously only something that could most likely have been caused by an accident, then it's not difficult to deduce what the cause is. If blood biochemistry is outside normal ranges it won't necessarily indicate what has gone wrong be it past/current infection, toxic, poor nutrition, environmental factor etc. 

With many horses that Roger is asked to treat, the symptoms are often more chronic and with a more insidious onset that has gradually worsened over a period of time. Very often, with the help of Professor Hindsight, the starting time can be appropximated and sometimes associated with an incident that wasn't thought to be significant at the time. Horses evolved to compensate very well so that they weren't singled out to be preyed upon by predators. In Roger's opinion many lamenesses will have started months before symptoms appeared. What we witness is the failure of the compensation mechanisms. This is why it is important to assess each individual in its entirety rather than just focus on an obvious site of injury. It could be the original problem, or it could be the compensation mechanism itself that has failed. 

The other issue that seems to be getting more common, especially in the equine world, is that a very high % of the total available budget seems to be spent on diagnostics, leaving little to nothing in the kitty for the then suggested treatment. Having used up the insurance allowance and the private funds insurance was supposed to safeguard, too many horses are abandoned with only a diagnosis, or partial diagnosis, which may not even have identified the root cause. Owners! You need to remember that the insurance policy is yours. It is finite and it is your responsibility to ensure that enough money is available to treat your horse after diagnosis. You must decide in discussion with your vet how much of your budget is for diagnosis and stick to it, or your vet will keep on going in order to find a diagnosis, and you risk not having sufficient funds available to treat your horse. If you're going to end up leaving your horse in the field for Dr Green to sort out with a bit of help from Time the Great Healer, you might as well choose that option first and save yourself a lot of time, money and stress. Of course, not everything will respond to field time either, so best to be much more careful about what procedures you give the go-ahead to in advance, and know what the scan, nerve block or whatever is going to achieve in terms of treatment options as well as costs. If conventional methods fail, you are more likely to still be able to fund an out-of-the-box approach.


Thermal Imaging

Having taken a thorough history and performed a thorough physical examination, Roger will often look for differences from the normal using a thermal imaging camera. Below are some examples of pictures that Roger has taken where thermal imaging saved a considerable amount of time and cost by quickly identifying areas that are not as they should be.

Be aware that thermal imaging sees and measures variations in surface temperature.  The skin surface can appear hotter because of external as well as internal factors. I have heard of some people using thermal imaging cameras who will try to diagnose very specific internal structure injuries from thermal images. I don't believe that this is possible to the degree of accuracy they would like owners to believe (and pay considerable amounts for). It is easy to misinterpret artifactual anomolies in surface temperature as being clinically significant when they aren't.

Thermal imaging is just one of the tools in Roger's toolbox that he uses in combination with other skills and equipment to help identify a problem. Combining thermal imagine with other techniques to see if both agree helps ensure only real differences are reliably identified. Even when genuine hotspots are identified it still doesn't tell you exasctly what has caused it. For example, if you see a hot spot on a hoof sole you cannot tell just from the image alone if its a bruise or an early abscess developing. Obviously, Roger wouldn't use thermal imaging if it didn't help reliably identify a problem area, but given the limitations as to what exactly it alone can diagnosed within an area identified, it is important to correlate all findings with other checks and information to corroborate a diagnosis.

Inflamed gaskin

The left gaskin is clearly much hotter (whiter) than the other muscular areas above. There is a tendency to blame lameness on a joint rather than on a muscle that has an action on the joint. Thermal imagine very quickly identified the problem area, but as I've been saying it doesn't necessarily tell us WHY that muscle is inflamed. Was it a kick/bang/fall? Has the muscle itself got a strain or tear? Has a thorn got in and set up a reaction? Identifying the area through differences in temperature is good but is often only half the story, if that.

In this case, there was no obvious skin lesion and it responded well to a couple of sessions of Scenar treatment without any further investigation necessary.

Inflamed Dog's Toe

It isn't always easy to use thermal imaging with a shaggy coat but this image clearly shows a hot area of inflammation mostly centred over the inside toe of the front left paw. The left paw looks generally hotter than the equivalent part of the right paw with most heat towards the medial side.

The dog wasn't lame enough to consider that an X-ray would be likely to see anything of note. MRI wasn't going to alter the treatment approach going forward, so wasn't considered necessary either.

Once again, Scenar confirmed the finding and successfully treated it alongside a supplement to help.

Hot or cold?

Comparing both hind feet of this horse looking from in front between the front legs, on first impression you would be forgiven for thinking the right hind foot was abnormally hot and inflamed.

However, looking at all 4 feet together tells us a different story. It is the left hind foot that is significantly cooler than the rest. It could of course be 3 hot and inflamed feet, but the history, presentation and lameness gait didn't suggest this. A cold leg/foot signals reduced circulation - but why?!