Diagnostics

When a sick pet comes to see me there are a few things I can diagnose and treat based only on physical exam and the history I receive from the owner. Most illnesses, especially serious ones that appear rapidly require diagnostic testing to appropriately diagnose and treat. Even more frustrating for many pet owners are the illnesses that require more than one round of testing to reach an answer and an appropriate treatment plan. As veterinarians we sometimes become discouraged by this and fall into not pushing for the best diagnostics because we know how frustrating it can be for owners. This doesn’t do our patients any favors and in some cases it can lead us into treating the wrong diseases or it could extend the treatment of a disease costing our clients more in the long run than if we had just pushed for the more appropriate course of action in the first place.

For illustrative purposes we will pretend a dog is brought in to see us because the owner has noticed recently that the dog has lost some hair. The owner will stand quietly for a few minutes while I go over the dog and look at the skin showing through the sparse hair. As soon as I look up from the patient clients will often ask, “So what is it?” I understand the desire to know what the problem is but if it is just hair loss with no other clinical signs there are over 200 possible illnesses that can cause hair loss. Many of these are rare but the list is extensive.

If the dog is also itching at itself we can narrow our list of possible illnesses down to just under 100. So we’ve already ruled out over 100 illnesses before we do any diagnostic testing at all. Not too bad. If we add in just two more clinical signs we can narrow it down even further. Let’s say that the dog also has crusts and scabs in the areas of hair loss and that those areas have increased pigmentation. We can now narrow our list down to just over 25 illnesses. Now we’re talking! So we’ve gone from over 200 to around 25 and so far all the client has to pay for is the exam. This is going great.

It’s sort of going great. Now we have 25 different illnesses that we have to rule out before we begin treatment. This is where the job becomes challenging. I need to come up with the best diagnostic value for the client’s money. In this case we would start with scraping the skin to look for external parasites. We would also place tape on the areas of hair loss to look for fungi and bacteria. Total cost right now for the client is still pretty low. If those come back negative that means we don’t have a diagnosis or treatment plan yet but it also means we can narrow our list down even further. Now we have to think again about where we want to go next diagnostically.

My next step for this patient would be complete blood work including electrolytes and a urinalysis. Now we are spending money. We just likely doubled our bill and this still may come back as a big list of rule outs. In our line of work, however, rule outs are occasionally more important than diagnoses. If this dog has disseminated Mast Cell Tumor for example we are going to have some very difficult decisions ahead of us. It’s still entirely possible that this dog only has allergies.

Let’s say that the blood work came back with mild to moderate elevations in a few liver enzymes and a mild anemia. Well this narrows it down considerably but while it seems like it makes things easier our next step is going to be more specific. Many of our next steps will be costly and will only be ruling in or out a single disease. Here we choose to play the numbers and rely heavily on the owner’s history being very accurate. We recommend a skin biopsy. We have now increased the total cost to the client to over $600 and we still might end up with only allergies as a diagnosis.

The other road to go would be to just treat the dog for allergies and see what happens. This is leaves an uncomfortable amount of uncertainty and in some cases can end disastrously but every case is different. There have been plenty of cases where I have chosen to treat dogs for just allergies based on the history and physical exam and there have been a few cases where I have gone all the way to biopsy and then treated for allergies. There have also been cases where I considered treating for allergies, looked a little deeper and discovered diseases that might have been exacerbated by treating the dog as an allergic dermatitis. No two cases present exactly the same and some of the allergic dogs present exactly like dogs with some other more specific and serious illnesses. Unfortunately we aren’t able to attach our patients to a computer and have it spit out a diagnosis.

Please remember that we are often as frustrated as you are as we go down these diagnostic paths and sometimes maybe we take a wrong turn or two. I can say with complete certainty that I have never recommended a diagnostic test that I did not believe was necessary. That doesn’t mean I wouldn’t do a few things differently on a lot of cases if I got the opportunity. Hindsight is like that but as long as hindsight helps guide future decisions, it’s all part of the game.

Thanks for reading!

 

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