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VetInfo Digest July 2004

Table of Contents:

Common causes of:

Itchiness

Eye Problems

Lameness

Ear Diseases

Dental Odors

Nasal Exudates

Weight Gain & Loss

Coughing

Blood in Urine

Polyuria and Polydipsia

Things with no short list

New Stuff

General Practitioners and Specialists

This Month's Note:

Last month I said that the biggest advantage that a veterinarian had over clients was experience. This month I will try to give you an overview of the things we think of first when certain symptoms occur or when certain body systems are affected by disease or other disorders. However, in doing this I think that it is important to point out two things.

The first thing is that there is an old maxim in medicine that says "When you hear hoof beats think horses, not zebras." This is a way of saying that it is important to look for the most common causes of diseases and disorders first and then to look for uncommon causes later. It is simply more efficient to do this and usually it saves the client money, too.

The second thing is zebras really do exist. And when they run you hear hoof beats. So when you hear hoof beats and you're really certain that there are no horses around, you might want to remember to look around for those zebras!

Itchiness

When your pet is itchy the most likely problem is a flea infestation unless you are using a good flea control product on every dog and cat you own- and possibly even if you are.

If fleas aren't the problem the next most likely cause is allergies -- usually atopy (inhaled allergies) but sometimes contact allergies or food allergies. Itchiness that is seasonal is most likely to be due to allergies if fleas are not present.

Some dogs (almost no cats) have primary bacterial skin infections that can cause itchiness that is persistent and noticeable. This seems most likely in short coated breeds, especially bulldogs, Dalmatians and Labrador retrievers.

Sarcoptic mange (scabies) is a pretty common cause of itchiness for dogs in some places and less common in others. This usually causes intense itchiness and often dogs with sarcoptic mange can't resist scratching at themselves when their ears margins are rubbed. Sarcoptic mange is contagious and is the most common cause of itchiness affecting an entire group of dogs, other than fleas.

There are probably hundreds of causes of itchiness other than these and if these diseases are not likely it may be necessary to work through a pretty long diagnostic process.

Eye problems

The most common cause of either a dog or cat holding one eye shut is a corneal ulcer. This is an injury to the transparent layer of the eye and these injuries are very painful. They are also a legitimate emergency. If your pet is holding one eye shut it is really important to take your pet to your veterinarian to try to be sure that proper treatment is started immediately, if necessary.

The next most common cause of a pet holding one eye shut persistently is probably Horner's syndrome. In this case, the pet usually isn't actually holding the eye shut on purpose. Horner's syndrome causes the eye muscles to contract, pulling the eye back deeper into the socket and causing the lids to partially close.

The most common cause of sudden blindness in older cats is high blood pressure. This often happens as a secondary problem when kidney failure is present. If sudden blindness occurs in an older cat it is really important to test for high blood pressure or to treat for it even if testing isn't possible.

If an older dog's eyes are moving back and forth rapidly the most likely cause is geriatric vestibular syndrome. This is also accompanied by imbalance or inability to stand and walk but the eye movement is an important clue about the cause of the problem. This usually clears up on its own without treatment and is often mistaken for a stroke, so it is important to look for this symptom when balance problems occur. This can occur in cats but is less common in cats.

Swelling below one eye is most commonly due to a root infection of the fourth upper premolar tooth in dogs. Most people don't actually think this is an eye problem but enough do that it seemed best to include it here.

Keeping both eyes shut or partially closed is most often a sign of conjunctivitis. The most common cause of persistent conjunctivitis in younger dogs is probably allergies. Clear Eyes (tm) eye drops help some dogs with allergic conjunctivitis but many require cortisone based eye drops for comfort. The use of corticosteroid eye drops requires a visit to the vet in order to ensure it is safe to use the drops. In older dogs the most common cause of persistent eye irritation with mucus accumulation in the eyes is tear deficiency. Tear deficiency responds well in most dogs to the use of cyclosporin or tacrolimbus eye drops or ointment. In cats the most common cause of persistent conjunctivitis is probably chronic herpes virus (rhinotracheitis) infection. It can be helpful to use oral l-lysine to limit long term herpesvirus effects. Giving 500mg of l-lysine once or twice a day is best. Using the capsular form of the l-lysine makes it easy to open the capsules and sprinkle the lysine powder on the cat's food.

Lameness

Without question, the most common cause of sudden disuse of one rear leg in any dog over two or three years of age is a ruptured cruciate ligament. Most commonly dogs with this condition seem to be in pain the first day or two, then they refuse to use the leg but do not seem to be pained by the leg even when it is manipulated after that.

Also without question, the most common cause of lameness in cats in our practice is a bite wound that has caused cellulitis or an abscess. When a bite wound causes lameness it is important to take your cat to your vet for antibiotic therapy because these injuries can lead to tendon or bone infections that can persist for a very long time if left untreated.

Kittens and puppies both injure themselves playing pretty frequently. Often, clients believe that the puppy or kitten has a broken leg or serious injury due to the young pet's reaction to the injury. Most of the time these injuries are actually minor and the puppy or kitten is almost normal within a few minutes to an hour or so. There is nothing wrong with being cautious and having the puppy or kitten examined by your vet as soon as possible but it is OK to take the time to ensure the trip is made safely.

When there is lameness accompanied by pain that doesn't respond to pain relief medications it is important to consider the possibility of bone cancer in older dogs and less commonly in older cats.

Dogs with allergic skin disease can develop lameness due to inflammation or infection of the bottom of their foot in the area between the large foot pad and the toes or between the toes. This is usually referred to as interdigital pyoderma. Many of my clients seem reluctant to believe that this could cause severe lameness but it will. Think of having a severe sunburn on the bottom of your feet and trying to walk on it.

Another fairly common cause of acute lameness that can affect any foot of dogs is a torn toenail. When toenails break but do not come off there is a tendency for the remaining portions of the nail to trap the sensitive tissue around the base, leading to pain when the nail is touched or when the dog walks on the broken nail. This can lead to a sudden onset lameness in which the dog refuses to use the leg that has the torn toenail. It is always a good idea to check for torn toenails whenever there is a lameness without an obvious cause.

Ear Disease

Ear mites probably cause most of the ear infections in cats but if treatment for ear mites doesn't work very quickly, usually within a day or two, it is best to have the ears examined to make sure that an infection or other problem is not present.

Allergies are the underlying cause for most ear infections in dogs. Failing to recognize this and to come up with a good management plan for the ear disease often results in chronic ear infections or in ear infections that recur so frequently they may as well be one chronic problem. Sometimes ear infections are the only sign of allergy in dogs. We find that our patients do best when we work with the owner on recognizing early signs of ear disease, such as shaking the head, pawing at the ears, holding the head tilted towards the infected ear and sensitivity to touch around the ears. If these signs do occur then early intervention with medications to control inflammation and/or infection helps keep the problem under control. Overall using medications early and as frequently as necessary actually results in using less medication over the long run and having fewer problems, as well.

Older cats commonly have purple tumors in their ears that appear to be the result of chronic inflammation or irritation. We are not sure that there is a correlation but it seems like we see these more in cats who had severe upper respiratory infections as kittens. These cats also seem to have more wax buildup over the years, even though they may not have an accompanying infection.

Hematomas are swellings of the flap of the ear caused by rupture of a blood vessel between the cartilage inside the ear and the skin. These are pretty common in dogs and not uncommon in cats. Most hematomas appear to be due to flapping the ears in dogs and scratching at the ears in cats, but many occur without much evidence of ear shaking or scratching behaviors. A paper published in the 1980s suggested that many of these are actually due to an immune mediated disorder but I'm not sure that this has ever become a well accepted theory. Some hematomas seem very painful to the pet and some don't appear to bother the pet at all. Once in a while a bite wound on an ear or some other trauma leads to an infection that resembles a hematoma but this is usually easily recognized at the vet's. The standard procedure for treating these is to drain the blood from the hematoma and then to suture the two sides of the ear flap together to prevent it from filling up with blood again. Sometimes a pad or stabilizing device is included in the suture pattern. A nonstandard treatment that often works pretty well in dogs is simply to put the dog on prednisone therapy on an every other day basis until the hematoma heals. This works better for small hematomas that aren't painful than for big hematomas or ones that seem to hurt. The object of surgery or medical treatment is to prevent the ear flap from scarring into a crumpled "cauliflower" shape that obstructs the entrance to the ear canal. We haven't tried the prednisone therapy in cats because cats usually seem to have hematomas that affect the entire ear flap.

Dental Odors

It is very common for baby teeth to be retained in dogs and it occurs occasionally in cats, as well. Food trapped between the permanent and baby teeth can cause odors. Whenever there are two teeth that seem to want to occupy the same spot, it is best to have your vet examine your dog or cat. If a baby tooth is retained it should be removed. It is especially important to do this when there is a narrow base to the lower canine teeth making them impact slightly on the palate of the upper jaw. Removing retained baby teeth when this situation is present makes room for the permanent tooth to move outward, preventing long term problems with the lower canine tooth impacting on the upper palate.

Tartar accumulation is the most common cause of oral odors and can start before a year of age in dogs and cats. It is important to have the tartar removed on a regular basis and to try to prevent tartar accumulation by brushing the teeth or using treats, such as rawhides, large real bones or dental diets to lessen tartar formation. Dental care is woefully lacking in veterinary medicine, almost certainly due to the necessity to anesthetize almost all dogs and many cats to really do a good job of teeth cleaning. If we didn't have to anesthetize our patients to get good dental prophylaxis results I'm sure that teeth cleaning would be recommended every six months to a year, as it is in people. Every dog and cat has to be evaluated on a case by case basis to determine when it is best to go ahead and take the anesthetic risk in order to clean teeth - but if your dog or cat is over three or four years of age and has not had a dental cleaning it is likely that having this done would be a good idea.

At least four or five times a year we have a dog come in the office who has gotten a stick or bone wedged between the upper row of teeth -- from one side to the other. If this stick has been there long the odor can be truly awful. Usually these dogs are frantic about pawing at their face at first but many will give up on that rather quickly and have very little sign of a problem until the stick causes enough of an oral ulcer or periodontal disease that the dog starts to react to it. If your dog paws at its mouth make sure you open the mouth widely (or have your vet do it) and look for a stick caught across the roof of the mouth. If one is present it is OK to remove it if you can be remember that removing it may startle your dog, so be careful. This happens in cats on a much more rare basis.

Lots of dogs break the fourth upper premolar tooth, the largest tooth in the upper arcade, when chewing on hard objects. Usually these teeth have a "slab fracture" in which the outer enamel breaks off the tooth. This makes it easy for tartar to form and for root abscesses to occur. Often a strong oral odor is present. When the fourth upper premolar tooth has a root abscess it often causes a lump on the side of the face just below the eye. The lump may or may not have pus drainage. If your dog is reluctant to eat on one side or only develops tartar on the upper large premolars it is a good idea to look for one of these fractures.

Nasal Exudates

The most common cause of mucus or pus draining from the nostrils in kittens is feline upper respiratory disease complex, which usually consists of infection with one or more of the following diseases: rhinotracheitis (feline herpes virus), calicivirus, mycoplasma or bacteria. It is pretty common for kittens to have more than one of these diseases going on at the same time. This is the reason that we frequently treat kittens who have feline herpes virus infections with antibiotics. We know that the antibiotic isn't going to help with the virus but we hope that the antibiotic will help treat or prevent secondary bacterial infections.

The most common cause of mucus, pus or blood draining from the nostrils (especially if only one is involved) in older pets is probably cancer. Whenever there is persistent drainage from one nostril and no cause can be identified through examination and bacterial culture, it is best to look for cancer. It can be hard to identify a cancer affecting the nasal passages even with all the testing equipment available today. An MRI exam is probably the most reliable way to find cancer when it is present in the nasal passages, although it is often possible to visualize the cancer with an endoscope, as well.

Weight Gain

The most common cause of weight gain is not feeding proper amounts of food for the specific pet. Many times clients tell me that they "can't" feed their dog or cat less than they are already feeding it. The bottom line is that if a pet is eating enough to maintain or gain weight it can be fed less, no matter how small the amount of food being fed is. If a pet is receiving dry food as part of the diet or as the entire diet, measuring the food using a real measuring cup made for dry measure is the best way to determine how much is actually being fed. As a general rule we find in our practice that most pets need the lower end of the amount of food recommended in the feeding directions for most pet foods.

Weight gain does occasionally occur in disease processes. The most common causes of weight gain not due to fluid retention are hyperadrenocorticism and hypothyroidism in dogs. In cats these diseases are uncommon but sometimes a pre-diabetic weight gain seems to occur. Weight gain from fluid retention associated with heart failure and some forms of cancer can also occur. In cats this can also occur with feline infectious peritonitis and less commonly with liver disease.

Weight Loss

In young animals weight loss is often caused by parasitic infections. Checking for intestinal parasites and heartworms is always a good idea when there is an unexplained weight loss.

Weight loss in older cats is often associated with hyperthyroidism and with kidney failure. Diabetes is also possible. These conditions should be ruled out first when a cat is losing weight while continuing to eat normally. In the case of hyperthyroidism some cats eat markedly increased amounts of food but continue to lose weight. One of the major problems with weight loss in cats is simply missing the problem. It is important to weigh cats at least once a year when they get older and more often is better. A weight loss of one pound in a cat is often a 10% difference in weight, which can signal significant problems.

In older dogs and cats the most common cause of weight loss when all lab work is normal is cancer. Most of my clients find it odd that cancer can't be detected using blood counts and blood chemistry examinations like many other diseases can. In some dogs and cats with cancer calcium levels will rise but this is variable and doesn't happen often enough to make it a reliable indicator of cancer.

An odd cause of weight loss in both dogs and cats is itchiness in the warm months due to allergies. Dogs and cats may be so miserable they eat less and they are often very actively scratching at themselves, enough that the scratching really becomes a form of excessive exercise.

Coughing

In cats coughing is most commonly associated with asthma, heartworm disease and retching/vomiting that is being confused with coughing. It can be hard for veterinarians to tell the difference between retching and coughing in cats so causes of both problems have to be considered when cats are reported to be coughing. Coughing due to heartworm disease and asthma are pretty much identical on a physical examination and often the signs of heartworms can be confused with asthma on X-rays, making it important to consider heartworm disease carefully as a possible problem in areas in which it occurs, even if asthma seems more likely.

In dogs coughing can be due to a great number of problems but the most common causes of coughing in our practice are tracheobronchitis (kennel cough, bordetellosis), collapsing trachea syndrome and heart failure, including heart failure induced by heartworm disease. In areas of the country in which fungal infections are more common than in Virginia (generally areas with less heartworm disease) these infections have to be considered, as well.

Collapsing trachea syndrome is generally a problem in smaller dogs and it may occur at almost any age but does become more common as dogs age. It produces a harsh cough that almost sounds like something is caught in the dog's throat to many dog owners. Chronic heart failure is also more common in smaller dogs and also becomes more common as dogs age. Due to this it can be very hard to decide if chronic coughing in an older small dog is due to heart disease or collapsing trachea syndrome based on physical exam findings. It is often necessary to have X-rays taken or to use even more advanced diagnostic tests such as bronchoscopy or cardiac ultrasound examination to differentiate between these diseases or to demonstrate the both are present and contributing to the coughing problems.

Blood in urine

In cats the most common cause of blood in the urine is probably inflammation of the lower urinary tract due to crystal formation (usually struvite) in the urine or due to chronic interstitial cystitis. These are not bacterial infections and the course of these disorders is not affected by the use of antibiotics. In male cats it is estimated that less than 5% of the cases of blood in the urine and straining are due to bacterial infection. One exception is cats who have had a perineal urethrostomy procedure done (shortening of the penis and widening of the urethral opening). It is not uncommon for cats to have intermittent problems with bacterial cystitis (bladder infection) after his procedure is done. It is a good idea to have a urine culture run when your cat is having signs of urinary tract inflammation, so that other causes of urinary tract inflammation are considered if the culture is negative.

In dogs blood in the urine tends to occur most commonly due to bacterial infections of the bladder (cystitis), in both male and female dogs. In males another possible cause is prostate infection or inflammation. Cystitis is more likely in female dogs than in male dogs. Other common causes of blood in the urine are bladder stones and bladder cancer in dogs. If treatment for cystitis does not resolve signs of blood in the urine quickly and keep them away for some time it is best to look for these other conditions. X-rays are helpful in finding bladder stones but it may be necessary to obtain a biopsy sample through endoscopy, blind catheterization or surgery to confirm the presence of a bladder tumor. It is sometimes possible to find cancer cells in the urine and it is always worth taking the time to look at the urine under a microscope to look for evidence of cancer cells if cancer seems likely.

In areas in which heartworm disease occurs in dogs it is important to point out that heartworms can cause discoloration of the urine which resembles blood in the urine but is actually due to the breakdown products of blood. The urine actually looks somewhat like port wine when this occurs. Other disorders that cause internal bleeding can also cause this syndrome. We see this condition just frequently enough that it seemed best to mention it.

Drinking more and urinating large amounts of urine (Polyuria and polydipsia or PU/PD)

The most common cause of PU/PD behaviors in dogs are the use of corticosteroids, hyperadrenocorticism (Cushing's disease), kidney failure and diabetes. There are a number of other possible disorders. One that owners of intact female dogs should keep in mind is pyometra, or uterine infection. It is easy for vets to assume that a dog is spayed and to forget this condition might be a possibility. Remember to remind your vet that you dog is not spayed when PU/PD behavior occurs.

Cats who are drinking excessive quantities of water usually have diabetes or kidney failure or are being given corticosteroids, such as DepoMedrol (Rx) injections for skin disease or inflammatory bowel disease. Diabetes is most common in overweight cats during middle age and kidney failure is more common in older cats. Hyperthyroidism will occasionally lead to PU/PD behavior as well.

Not everything lends itself to short lists!

There are a number of conditions for which it is difficult to come up with a short list of possible causes. Vomiting and diarrhea are one such group of disorders. In these disorders it is necessary to sort through a large number of fairly common disorders. Standouts tend to be more likely with very particular circumstances. An example of this is parvovirus in puppies, the most common cause of severe lethargy with blood tinged liquid diarrhea in puppies. Even in this case it is important not to overlook hookworm disease and other intestinal parasites as possible causes of the diarrhea, though. These groups of disorders are best approached by the use of a methodical approach to diagnosis that includes a way to rule in, or rule out, the most likely possibilities.

Don't forget the Zebras!

One of the problems in medicine is the fact that as veterinarians become familiar with practice they tend to look more and more to the "usual suspects" and are thus less likely to find a less common problem early, or in some cases unlikely to find a less common problem at all. This is a tendency that works to the advantage of the majority of clients and patients because it saves money and it saves the stress and morbidity associated with laboratory testing procedures. However, it also puts the smaller number of patients who do have less common disorders at more risk of their illness being missed entirely. There is a great deal of usefulness to the simple question, "If this isn't what you think it is, what are the other possibilities?" Most veterinarians can produce lists of other possible diagnoses in their head pretty quickly and just going through the motion of making the list will sometimes help in ensuring that a less common disorder is not missed.

New Information and New Stuff

For some time there has been suspicion that lawn chemicals might play a role in causing cancer in dogs. A recent study done by veterinarians are Purdue University validates that suspicion, at least partially. There appears to be a connection between the use of herbicides and transitional cell carcinoma, a form of bladder cancer, in Scottish terrier dogs. It is unclear whether this link applies to other dog breeds. Lawn chemical companies advise keeping dogs inside until after these products dry. It is not known which chemical or combination of chemicals leads to the increased susceptibility for cancer in Scotties at the present time.

Intervet (tm) has won approval for a porcine based insulin, Vetsulin (Rx). This should be a significant improvement in insulin therapy for dogs who have had insulin resistance problems using human based insulin products such as Humalin (tm) since the porcine insulin is closer in composition to canine insulin.

General Practitioners and Specialists

For some reason a controversy seems to be brewing between general practice vets and specialists in veterinary medicine. This has been the subject of several recent articles in veterinary news magazines and on the message boards of some of the veterinary organizations online. It may be helpful to discuss some aspects of this controversy so that you will understand why your vet may be reluctant to refer to a specialist in some instances. This may help if it seems necessary to insist on a referral.

Specialty practice in veterinary medicine was almost completely limited to universities, with just a few exceptions, when I graduated from veterinary school twenty-five years ago. This created a situation in which veterinarians who just wanted to practice a specialty felt left out because specialists were expected to be researchers, teachers and specialists in a specific field. It also led to the board certification requirements for most specialties to lean heavily towards academic based requirements, such as requirements to have published research in order to apply for specialization. Many older veterinarians in general practice who desired to work in specific areas simply limited their work to those areas, such as orthopedic surgery or dental care but were unable to advertise or call themselves specialists due to practice acts restricting the use of these terms to veterinarians who are board certified in the claimed specialty. Many of these vets are as good in these fields as any of the recognized specialists. A veterinarian who feels quite correctly that his or her skills are equal to or surpass those of some specialists in the area in specific fields is obviously going to be reluctant to refer to a specialist.

Many veterinarians have had the experience of suggesting that a client get a second opinion from a specialist only to find that the client is reluctant to travel to a specialist but takes the offering of a referral as a sign that their veterinarian isn't sure of the diagnosis or treatment necessary for their pet. So instead of going to the specialist they go to another veterinarian in the area. This is reasonable but can be a problem for a veterinarian who knows that a surrounding veterinarian is not as capable in a specific field or practices with a markedly different philosophy. Knowing that your client is going to someone who is going to disagree with you immediately, regardless of the situation, isn't a good feeling. If you can't go to the specialist but see the need for a second opinion, it may be best to ask your vet which other vets in the area are the best choices for a second opinion.

Specialists sometimes become quite dogmatic about certain things. We have specialists in our area who routinely run all the tests that we have already run again, simply because they can't bring themselves to believe that our in-house laboratory produces accurate results or because they don't use the same pathologist when microscopic examination of tissues is necessary. This can add significantly to the cost of seeing the specialist and can be a sore point between the veterinarian and the client who fails to understand that their vet was doing the right things and the specialist is just insistent on doing them again. It is also a problem when the general practitioner understands that there are monetary limitations and has to decide whether to try to make a diagnosis or to ask the client to see the specialist early on in the diagnostic process in order to conserve money. This can lead to situations in which the specialist points out the deficiencies in the diagnostic process of the referring vet -- who knew better but was honestly trying to help the client.

As more and more specialists go into private practice, often without going through a stint at a university, some of these differences should resolve. The increased availability of specialists will make it easier to refer to them quickly and as specialists start out in similar practice situations to general practice vets their empathy for each other should improve. In the meantime, if you think your pet needs to see a specialist insist on it -- but try to listen to your vet's opinion about which specialist would be best to see.

Thanks for Your Support!

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