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VetInfo Digest July 2005

Table of Contents:

Instant Diagnoses

Dogs

Cats

Why are Vets Reluctant to do Diagnostic Testing Sometimes?

Should all Vets Run all Tests?

This Month's Note:

I tore the meniscal cartilage in my left knee this month and so I have spent a lot of time being the patient rather than the doctor. This is a good thing, occasionally, for a doctor to go through. It gives me a lot more empathy for my patients with cruciate ligament injuries and other knee (stifle) injuries. It also makes me appreciate kind care over brusque care and how much the staff at a clinic impacts the overall experience.

Over the years I have had the opportunity to become more empathetic with my patients over a number of health issues. Each time I am surprised by how little I really knew about how an injury or disease really feels or the activities that are inhibited by it.

While I' personally glad that most of the time I' not a patient I have to admit that I often come out a better doctor for the experience. When your vet is out of work for a few days with an illness count your blessings and remember that in the long run it might be a good thing!

Just Tell Me What's Wrong!

Some of our clients become very frustrated when they talk to my receptionist on the phone and give symptoms they are seeing in their pets without getting a diagnosis over the phone from my receptionist. There are a couple of reasons why this occurs. The first one is that it is illegal for my receptionist to give a client a diagnosis over the phone, even if she recognizes the symptoms as part of a particular disease process immediately. The second reason is that there are very few symptoms that point to one and only one diagnosis. Most of the time there are several possibilities and it would be a mistake to presume that a diagnosis could be made over the phone. Finally, my receptionist really feels that the best course of action is for me to make the diagnosis and for her to set up the appointments. This seems so logical that she is frequently amazed that it doesn' occur to the client on the other end of the phone.

Of course there are lots of times when we can make a pretty good guess what is wrong with a dog or cat based on a very good history and the symptoms that are occurring. There are even a few disorders for which the client complaints are so repetitive in nature that my receptionist can make an accurate diagnosis, most of the time. So this month I thought I' give a list of the things that we hear over and over again that really do point to specific diagnoses. It is a relatively short list because there aren' too many disorders that we get a strong feeling about just from telephone conversations. It is important to remember that even though we often do make the right call from just a few words on the telephone it is still not legal or ethical to make the diagnosis over the phone. It is necessary to see a pet in order to ensure that the caller doesn' have the occasional pet who really does have something else.

Dogs

When a pet owner calls us and says that their overweight middle aged female (less commonly male) dog is holding one rear leg off the ground most of the time, or just barely using it, but that there doesn' seem to be any sign of pain or discomfort when the leg is touched or manipulated we generally find that these dogs have anterior cruciate ligament (ACL) ruptures. In dogs ACL injuries tend to be degenerative rather than traumatic, although both can occur. This means that most of the time there is no distinct event that can be pinpointed as the cause of the rupture. The ligament just gives way due to slow deterioration over time.

" dog has a bone caught in his throat." This almost always means the dog has tracheobronchitis, commonly referred to as kennel cough. Once in a while a dog actually does have something lodged across the roof of its mouth, usually right between the big premolars on either side or lodged in the soft palate but 99 times out of a 100 when clients think their dog has something caught in his throat they actually have tracheobronchitis.

If your dog is suddenly lame on a front foot (usually) and won' put the foot down and really prefers that you not touch its foot it probably has a torn toenail. When toenails crack near the nail bed or get partially but not completely torn off from the nail bed most dogs will try hard not to put the foot down at all. Removal of the damaged portion of the nail usually resolves this problem almost instantly.

When clients call and tell us that their dog's tail hangs limp and doesn' move but they can walk normally, we suspect one of two conditions. If the dog is a Labrador retriever on a hunting dog we suspect a condition referred to as " tail" This is loss of sensation in the tail due to swelling in the muscle compartments and usually goes away on its own. If the dog is a small dog or a big dog with a history of trauma we suspect " jerk" which occurs when the tail stops but the dog keeps going, resulting in dislocation between vertebrae in the tail. This condition may or may not respond to treatments and sometimes the tail must be amputated. This condition is very common in cats, as well.

Hairloss in a "Christmas Tree" pattern starting at the base of the tail and extending in a triangle with a point around the last rib is almost always due to flea allergy. It is not uncommon for these dogs to have no visible flea problem. They are often so bothered by fleas that they are experts at catching them and removing them from their body. The tell-tale hairloss and itchiness may be the only symptoms.

Clients frequently call us and tell us their dog has had, or is having, a stroke. This almost always means that the dog is having a condition referred to as peripheral vestibular syndrome, in which there is a loss of balance or coordination. It is not unusual for affected dogs to be unable to walk or drink water as they are simply too uncoordinated to accomplish these tasks. Fortunately, peripheral vestibular syndrome is almost always self-limiting and most dogs recover within a few days to a few weeks.

When your dog' ear looks like it has swollen up like a balloon it almost certainly has a hematoma, which is caused by blood leaking into the space between the skin on each side of the ear. This happens in cats, too, but it is less common in cats.

Dogs who drag their rear ends across the carpet or ground almost always have impacted anal sacs. Once in a while this is a symptom of allergies or tapeworm infestation but usually it is due to anal sac impaction. Some dogs will successfully express their anal sacs through this behavior but if it goes on for more than one day, even intermittently, it is best to have the anal sacs checked by your vet, unless you are familiar with anal sac impaction and able to express the sacs at home.

When dogs have a small swelling with drainage from it just below one eye it is almost always due to a tooth root abscess, unless there is a known traumatic event such as a dog fight.

Cats

When people call us and say that their middle aged or older overweight cat has suddenly started drinking a lot of water, has a greasy feel to its hair and is getting even more lethargic than usual we think about diabetes mellitus. In our practice we see diabetes slightly more frequently in male cats.

Clients frequently call us about older cats who have great appetites, seem active but continue to lose weight. This set of symptoms is highly suggestive of hyperthyroidism, or too much thyroid hormone in the circulation. Most cats with hyperthyroidism are over 9 years of age but it can occur as young as five years of age in some cases.

" My 10 year old cat is suddenly blind." The most common cause of sudden blindness in older cats, by far, is hypertension (high blood pressure). Hypertension occurs as a primary condition in some older cats but it is more commonly associated with either kidney failure or hyperthyroidism. Peaks in the blood pressure can cause retinal hemorrhage and retinal detachment, leading to a very sudden onset of blindness. If the blood pressure is controlled promptly and successfully, within 48 to 72 hours, there is a very good chance that sight can be preserved.

"My cat has hairballs" most commonly means that a cat has inflammatory bowel disease. This may respond to some treatments traditionally thought of as hairball remedies --- but the underlying reason that hair isn' being passed through the digestive tract as it normally would be is usually inflammatory bowel disease.

"My cat has suddenly gone crazy, she' crying and rolling and won' leave me alone." OK, for this one a hint - this is usually a 7 to 9 month old female cat. If you have never seen a cat in heat it is hard to explain just how frantic some of them can be.

When a client calls and says their cat tries to bite them when they touch its tail the most common cause of this is an abscess at the base of the tail. Once in a while this can be due to tail injuries or an unusual condition referred to as feline hyperesthesia syndrome. The difference is between abscess pain and hyperesthesia syndrome is that the cat is immediately painful with an abscess but often tolerates a short bit of touching or petting with hyperesthesia syndrome and then suddenly bites the hand that is stroking it.

Both dogs and cats get tapeworms but we get most of our calls about cats "with little worms crawling around their rear end" There are only two worm types that people really see, roundworms and tapeworms. Roundworms are often passed whole or thrown up and they are about 2 to 5 inches long, white and distinctly "worm like" What people see when tapeworms are present is a muscular egg case that contains tapeworm eggs but can move around a little on its own through muscular contractions, which also push the eggs out of the case, spreading them around the environment. These egg cases or tapeworm segments are about ½ to ¾ of an inch in length and appear rectangular. They are white to off-white when first passed but dry up to look like yellow rice granules that are often found stuck to the hair around the rectum. This is perhaps our easiest " the phone" diagnosis --- but we still have to have a doctor/patient/client relationship to treat the affected pet!

When Your Vet is Unwilling to Run Specific Tests

People write me fairly often with questions about why their veterinarian will not run a particular test or diagnostic procedure when they have asked their vet to run the test. This happens with all sorts of test procedures so it is not just one particular test that bothers a lot of veterinarians. I am not sure that I am the best person to explain this reluctance overall, but I can explain why I am reluctant to run some test procedures and a little of the philosophy that might lead to disagreements between vets and pet owners over test procedures.

One of the simplest questions I get asked is why a veterinarian won't test a puppy for heartworm disease or a kitten for feline immunodeficiency virus. Neither of these tests is reliable prior to 6 months of age.

Heartworm tests can only detect adult female heartworms. It takes almost six months for a heartworm to become an adult, so testing prior to this age is simply a waste of time. In addition to this, if the puppy was born in a time when heartworms aren' transmitted in the area it lives in, which is often up to six months of the year, it may be necessary to further postpone testing in order to ensure that the puppy is old enough to actually have heartworms.

Feline immunodeficiency virus can only be detected by antibody testing. If a mother cat passes on antibodies to the virus to a kitten, the test result will be a false positive. If the kitten is tested prior to the time that antibodies have had time to form against the virus the test will be a false negative. Since this process takes several months it is generally agreed among infectious disease specialists that it isn' a good idea to test for FIV prior to 6 months of age as the results are unreliable.

Some tests just aren't very good, even though they exist. A prime example of this is any test that is billed as a test for feline infectious peritonitis (FIP). This virus is indistinquishable in testing from the much more common feline coronavirus. A positive test result simply indicates exposure to feline coronavirus and does not prove or disprove the presence of FIP. Some vets feel that they can interpret the results based on the clinical signs the cat has or by certain titer levels but the bottom line is that these tests can not definitely rule in or rule out FIP, making many veterinarians very reluctant to run the tests at all.

There are very good tests for specific diseases that are still somewhat confusing to interpret. This can make veterinarians reluctant to run these tests in some circumstances. A good example of this type of problem is testing for feline leukemia virus (FeLV) using an ELISA screening test in a cat who appears to be healthy. This test has about a false positive rate of about 4 in 1000 cats. That doesn' sound very high but when it is viewed against the probability of feline leukemia virus in a healthy cat, which is also about 4 in 1000, a dilemma starts to develop. If 4 out of 1000 cats are truly positive and 4 out of 1000 cats have a false positive result, the predictive value of this test is around 50% -- only about half of healthy cats who test positive for feline leukemia virus actually have the disease.

The predictive value for cats who are sick, especially young cats who are sick, is much higher. A young sick cat is much more likely to actually have feline leukemia virus. The incidence of FeLV in this population of cats is probably closer to 20%. In this case, for every thousand cats tested about 200 will actually have FeLV and there will still be 4 false positives. Now the predictive value of the test is a lot higher, about 98%. In this circumstance it may not be necessary to confirm the screening FeLV test with a more accurate test but it is still advisable if you wish to be cautious. We just had a positive screening test in our office in a young male sick kitten last month and the more definitive testing was negative when it was run at the reference laboratory.

Many vets are reluctant to run feline leukemia screening when a cat appears to be healthy because it is really hard to explain the concept of predictive value in testing to some clients and it is also hard to explain why a test was run when you are reluctant to believe the positive result and want to confirm it with another, more expensive, test. It is critically important to retest a healthy appearing cat with a positive ELISA based FeLV test result. There are tests that are more specific (less likely to have false negative results) but they aren' really good screening tests because they are expensive and have to be sent to specialized laboratories so the results aren' immediately available. The time spent explaining why further testing is necessary is inconvenient when office visits are scheduled every 15 minutes. There is a small chance that the cat owner will be freaked out by the positive test and will abandon the cat to a shelter or insist on euthanasia unnecessarily. All these things combine to produce a reluctance to test for FeLV in a cat who appears to be perfectly healthy, at least for some vets. It probably isn' right to make that decision for the client. It is almost certainly better just to explain the consequences of a positive test result and to go ahead and test when the client is concerned -- but the temptation to avoid controversy or to increase one' workload just sometimes wins out.

Some tests are hard for veterinarians to understand or to interpret. Running a test when you aren' sure what to make of a positive test result can be very disconcerting. In our area a good example of this type of test is the in-office test for Lyme disease. There is a relatively new test for this that is supposed to be very accurate at detecting actual exposure to borreliosis (Lyme disease). However, the key word in this sentence is exposure -- it doesn' necessarily indicate that an infection is currently present or whether clinical signs of Lyme disease will ever occur. We sometimes get positive Lyme disease test results in patients who have not left our immediate geographical area. This is an important part of the history because we have never recognized a case of Lyme disease in a pet who has spent its life in our immediate practice area. We have seen cases in dogs traveling with their owners and in dogs who spent part of the year in our neighborhood and part of the year elsewhere. So how do we interpret a positive Lyme disease test? Is is just something to note in the record and ignore or should we be treating patients who test positive despite the lack of clinical signs? This is tough to figure out. We aren' even sure what to do for the patients who test positive who live part of the year in areas in which Lyme disease does occur as there is no strong consensus among infectious disease specialists at the current time. Without some idea of what to do for patients who test positive it is easier just to skip the testing so that we aren' confused by the results and so that the pet owner isn' upset over our confusion about what to do.

There are times when having a specific diagnosis just doesn' do any good for the patient. The best example of this type of test result is probably biopsy of a potential cancer in a pet whose owner has already stated an unwillingness to pursue therapies such as chemotherapy, radical surgery or radiation therapy. Does it really matter what type of cancer is present if the patient' owner isn' going to pursue treatment, anyway? Some vets argue that it does, because knowing the exact cancer might influence the owner' reluctance to treat. If a cancer is present that responds well to treatment that might overcome the owner' objections, for instance. In addition to this, there are times when a malignant cancer is strongly suspected based on clinical signs but the biopsy report doesn' support this diagnosis. In that case it might be necessary to look for another cause of the clinical symptoms and if one is found, the pet' life may be vastly improved. The odds of this kind of good outcome are pretty low but there is some justification for testing -- just enough to make it likely that one vet might want to test while another really prefers not to.

Some disorders have elements of both of the preceeding problems. An example of this is testing for hyperadrenocorticism, or Cushing' disease. There are several possible test procedures for this disease and they all have some advantages and disadvantages. In addition to this, there are times when it doesn' make a lot of sense to treat the disease and other times when it seems critical to treat it if it is present. This produces a situation in which a veterinarian may feel that the testing procedures are not specific enough to warrant testing without a very high degree of suspicion that the disease is actually present. Some veterinarians want to weigh the dog' overall condition prior to trying to test for this disorder. If the patient seems likely to benefit from testing, such as a patient who is in good condition but is miserable due to the excessive thirst or secondary infections that frequently accompany Cushing' disease the vet might push for testing.

A patient who has some signs of Cushing's disease but nothing that seems bothersome to the pet might prompt the same vet to seek to delay testing until treatment was definitely warranted. Finally, a patient who seems to have Cushing's disease but whose overall condition is so poor that recovery from that alone won't make the pet's overall condition might make the very same veterinarian discourage a pet owner from testing for the disease or seeking treatment for it.

Specialists sometimes advocate testing that general practitioners tend to view as dangerous to the patient or that may have risks that exceed the expected benefits of testing. There are several conditions in dogs and cats for which kidney biopsy is necessary for a definite diagnosis. There is a fair amount of evidence to suggest that kidney biopsy is not a completely safe procedure, as it has immediate risk of severe bleeding and long term risk of reduction in the kidney mass, a critical problem in a patient who already has a reduced kidney mass. It is easy to find recommendations to consider kidney biopsy prior to treating for specific kidney diseases but when weighed carefully, it is evident that treatment on a trial and error basis may actually be safer for the patient. Testing in this situation becomes a true ethical dilemma for some vets --- to recommend a kidney biopsy is to take a chance with a patient' life but not to do it may mean treating for disease without proving it is present, something most veterinarians would like to avoid doing, if possible. These type of tests can put a veterinarian in conflict with a client over what is best for a patient.

It is harder to understand reluctance to do general blood count and blood chemistry testing or testing for conditions in which the results are very clear cut, even if the disease being tested for is rare or expensive -- as long as the pet's owner understands this and wants to proceed with testing. I do get correspondence from people whose vets have apparently refused to run lab work that seemed very reasonable to me. If a pet owner is worried about the possibility of kidney disease in an older cat simply because it is common this isn't an unreasonable request even if no symptoms of the disorder are present. The same is true for genetic conditions that affect certain breeds, such as hemophilia, von Willebrand's disease, persistent retinal atrophy or polycystic kidney disease. These types of disorders can be worrisome for the pet owner and it is reasonable to test for them, if a request is made.

There are a number of reasons why veterinarians might not want to run tests that are not likely to be harmful to the pet even though the client really would like to do the test in an effort to understand more about a pet's condition.

It is likely that in some cases the reasoning is simply that the disorder seems unlikely to the veterinarian and so spending money to test for something that isn't very likely seems like a bad idea to the vet. The only real counter to this argument is that it is the client' money and therefore the client's decision on whether to spend it.

Veterinarians have a tendency to try to control the cost of pet care, even if it doesn't look like that to most clients. It is pretty obvious to any vet who has practiced for several years that some pet owners are very enthusiastic about caring for their pets for a year or two and then become reluctant to spend money on a pet, apparently having the feeling that they aren't getting enough for their money or that the veterinarian took advantage of their enthusiasm. So they stop coming in for care or they switch veterinarians in the hope of finding someone who will treat their pet without insisting on a proper diagnosis first. The long term effect of excellent early care in this case is poor long term care. Veterinarians frequently try to manage the costs of maintaining health care for their patients, hoping that this will ensure a good long term relationship, knowing that this model keeps the most clients coming back, even if a few leave because they really did want to spend money testing for something just to make themselves feel better about their pet's situation. It is odd, but in this situation the clients who should be the veterinarian's favorites for their devotion to their dog end up being the ones who make the vet the most nervous and stressed because the veterinarian is worried that the concern will turn to disappointment when test results are not productive in identifying a disease every single time they are run.

Testing, and explaining test results, takes up a fair amount of time. There are lots of days when it is hard to devote that much time to a particular patient. On these days there is a tendency to try to get by without testing, if it seems like the risk to the patient is small. This is a particularly bad trap for veterinarians to fall into because it can lead a veterinarian into an unrealistic assessment of his or her ability to make an accurate diagnosis. It is easy to believe that your diagnostic skills are very good if you never test them.

When veterinarians test for conditions and they are not present, despite a diagnosis that suggests they should be, the situation can be confusing for the client and embarrassing for the veterinarian. Sometimes a veterinarian really doesn' want to check to see if their initial diagnosis is correct simply to avoid having to explain how they could have been wrong in their initial diagnosis. I have most of my clients pretty well trained to expect that lab values might not support my initial thinking. To me, this is a good thing --but I know that I have lost clients who expected me to be right 100% of the time right off the bat. The best way to be right 100% of the time is never to look too critically at your work and to assume that you are correct! This can make the owner feel great about their vet' diagnostic skills and ability to diagnose things without spending a lot of money but it can be really bad for some of the patients. I have used this statistic before, but even in veterinary teaching hospitals it is estimated that the initial diagnosis made at the time of first examination is wrong about 50% of the time.

Every now and then test results put the veterinarian in a situation in which the next logical step is referral of a pet to a specialist or veterinary teaching hospital. If this threatens the vet for some reason, such as a pre-existing conflict with the specialist, the veterinarian might be unwilling to do lab testing that might contribute to a decision to use a specialist. There are a small number of veterinarians who will not refer a patient except under extreme duress. Within this group there are some vets who simply decide that the best way to avoid having anyone else look at their patients is to control the diagnostic process entirely, in part by avoiding any test results that might not agree with their own assessment of the situation. It can be very hard for a pet owner to know when they are dealing with this type of veterinarian but one good hint is the ability to make a specific diagnosis at the end of every single office visit involving a sick pet. There is no veterinarian, anywhere, who can really do that. There are a small number of vets who believe they can, though. These veterinarians should be avoided if possible.

In the end, when analyzing whether or not to ask for or even insist on specific tests, the first step is listening carefully to your veterinarian's presumptive diagnosis and his or her plan to confirm that diagnosis and to treat the pet in the meantime. Sometimes you' find that it really does make sense to postpone testing until the response to treatment can be assessed or until symptoms worsen somewhat. Other times you will find that you really feel the need to rule out some condition that your vet isn't too concerned about. If not knowing for sure that leptospirosis serology is normal or not knowing whether your cat has feline immunodeficiency virus is really bugging you , ask your vet to test for the disorder. If your vet objects, ask why. If the reasoning is simply economic and you want to pay for testing in order to have more peace of mind, it is reasonable to insist on testing.

Most vets are willing to explain their reasoning when they are reluctant to pursue specific testing procedures and most will test for things they think are unlikely as long as they believe you really understand that the cost/benefit ratio for the particular test is very low. If you vet won't work with you when you request a test that it reasonably safe to run and which might provide benefits, no matter how small the probability of that is, then you have to decide if your vet is good enough that you will live with these conflicts in order to keep working with them or if the need to have some input is strong enough that you need to find a new veterinarian.

While I was driving to work today I heard a short discussion on the radio about why cancer therapy has become so much more successful in people over the last five years or so. Apparently there has been a great improvement in success rates in this short period of time. The doctor being interviewed said he thought it was mainly due to the internet. Cancer patients are much better informed about their diseases, the testing procedures available to them and the options in therapy that are available to them. In addition, successful therapies have spread more rapidly with the greater exchange of information. The time for being a passive patient, or in the case of pets a passive patient guardian, are past. No doctor or veterinarian can keep up with all of the available information on diagnostic and treatment options. Informed pet owners are going to start shaping the way that veterinarians pursue a diagnosis and therapy in the same way that informed cancer patients have already transformed cancer therapy in people. You have a much greater opportunity to influence your pet's medical care than ever. It is a big responsibility but in some cases, if you stay informed and understand the risks and benefits of test procedures and medical procedures you can make a big difference in your pet's medical care.

Costs of Testing—Is it Reasonable to expect your vet to be able to perform all test procedures?

One of the things that people who write to me seem to want to know is why their vet can't run specific tests that they have read about. The cost of providing some testing procedures can be prohibitive. Sometimes test procedures require continued practice and veterinarians just don't have enough cases of a particular type of problem to do the test well in their office.

We recently purchased a cell counter for doing CBCS (complete blood cell counts). The machine cost approximately $18,000 and it costs about $4.00 for us to run a sample through it at the volume of testing we anticipate. We doubt that this machine will ever make money for the practice on its own, but it allows us to have results quickly and to make diagnostic decisions that may be very important for our patients. So we purchased it. We could just as easily have decided that almost all of our patients would be unharmed by a 24 hour wait for CBC results and opted to send the tests to a reference lab. Economically that probably makes more sense and it is hard for me to say vets who chose that option in small practices are wrong. I just can't stand waiting 24 hours for results.

It took me almost five years after I was convinced that testing for high blood pressure in cats was important to purchase the machines necessary to test cats for hypertension. I wasn' worried about the cost of the machines, as the least expensive one was only about $800. I was really worried that I would not ever be able to accurately interpret the results because I wouldn't get enough practice unless I simply tested all older cats, even if I wasn't suspicious of hypertension. Lots of vets make exactly that kind of choice, either to pay for the cost of the machinery or to be able to maintain competence in a test procedure. I could never really justify charging everyone with an older cat for a test that would benefit only a few of them but again, I understand why some vets make that decision. As it turned out, we have gotten more consistent results with the blood pressure measurements than we anticipated and blood pressure testing has been a useful addition to our practice.

Our practice is somewhat unique in that we started out at a time when it was simply not possible to refer our clients to an emergency clinic for night time emergencies or to rely on specialists for complex diagnostic procedures since the closest specialist of any kind was over 200 miles away. We are still rural enough that we have to provide emergency services during the day and we have to be prepared to deal with some complex problems that might be better off being treated at a referral center. It is just the nature of the rural mindset. So I buy more testing equipment than is economically justified and I try to charge enough to make it possible to own the equipment and use it properly. Some vets can' do this and some veterinary clients prefer their vet not buy equipment that increases costs. There is a place for both philosophies.

In many areas of the U.S. and the world it will not be possible to find a veterinarian who provides a specific advanced diagnostic test, such as an MRI scan, nuclear scintigraphy or even something like ionized calcium measurement. It is almost always possible to arrange to have test procedures done if you are willing to spend the necessary money and to travel with your pet. It can be a hard choice but it just isn' possible for every vet to have the ability to run every possible test procedure. Sometimes you just have to go to someone who can run the tests you need, even if it means making a long trip. This doesn't always reflect on the overall quality of your vet's practice so don't be too judgmental when your vet doesn't have the ability to run one specific test procedure.

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The opinions expressed in this newsletter are those of Michael Richards, DVM., author.