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VetInfo Digest August 2005

Table of Contents :

Basic Facts:

Kidney Failure

Hyperadrenocorticism

Diabetes mellitus

Feeding Pets

This Month's Note:

The issue of medical mistakes has been prominent in the news lately. There are efforts underway in human medicine to find ways to prevent medical errors. It is unlikely that error can ever be banished from human or veterinary medicine, though. There are too many variables and too much that we really don't understand yet to expect human physicians or veterinarians to practice without making mistakes. It is a good goal to try to help doctors and vets reduce errors in diagnosing and treating patients but it is important to remember that the potential for a misdiagnosis or inappropriate treatment choices always exists. It is also important to remember that even appropriate diagnostic testing doesn' always yield accurate results and that appropriate treatment doesn't guarantee success.

You can help to protect your pet from medical errors by being an able advocate. This isn't as hard as it sounds. Pick a vet you are comfortable communicating with. Your vet should listen to you and respond to your concerns in a way that shows that your opinion matters. You should be willing to take the time to understand your pet's condition and you should take the time to recognize whether advice you receive from sources other than your vet is likely to be valid advice. When you are certain, discuss your concerns with your vet and bring your evidence. One of the hallmarks of a good vet is knowing when to listen to others!

Basic Information for Selected Problems

A number of subscribers have written to me over the years asking for simplified versions of diagnostic and treatment advice for a number of conditions. These letters often say something along the lines of " give me the facts I need to know." Most of you probably recognize that I'm not really all that good at limiting information to a few relevant facts and moving on. I am going to try to do just that this month, though. There are a fairly small number of disorders that come up over and over again in questions from subscribers and letters to Michal asking for help locating information on the web site. For many of these conditions people really are looking for a condensed guideline covering the important diagnostic tests and therapeutic options. The following information covers some of these diseases with emphasis on the things people really seem to want to know about them.

Kidney Failure in Cats

Kidney failure in cats is fairly common and there are a large number of options for therapy. There are a large number of things that can be done to help cats who are suffering from kidney insufficiency or kidney failure. It is critical to pick and choose among these options to ensure that the individual cat gets the best care for its individual needs and that the care doesn' exhaust the ability of its care givers before the cat's kidneys finally do fail completely. It is extremely important to understand that for most cats it is not going to be necessary or possible to use every therapeutic option. It really is possible to make the cat's life miserable by trying too hard to treat it and when this happens many owners give up all treatment rather than falling back on therapies their cat tolerates and they can handle. Please keep this in mind while reviewing this list of treatment options.

Fluid therapy: This usually means subcutaneous administration of fluids designed to keep the cat hydrated and to meet electrolyte needs. This is the mainstay of therapy for kidney failure in cats. It is critically important to maintain hydration in cats with any degree of kidney insufficiency.

Dietary modifications: There is still a lot of argument among veterinary nutritionists about the best way to handle dietary modifications to ensure that the kidneys have the best chance.

At present it seems that the mainstream opinion is that restriction of protein levels and phosphorous levels may not be absolutely necessary until the BUN is greater than 85 mg/dl or the creatinine greater than 3.5 mg/dl.
Staying away from foods that acidify the urine ( most of the foods that say they maintain urinary health in cats cause urine acidification. They are meant for cats with lower urinary tract disease, not kidney disease).
Changing from dry food to canned food is beneficial because it increases water intake

Phosphate binders: Medications or supplements that bind phosphorous and keep it from being absorbed in the digestive tract can be very beneficial for cats with kidney insufficiency. Examples of these include Amphogel (tm), Renagel (Rx) and even Tums (tm).

Potassium supplementation: Many cats with kidney failure have low potassium levels in their blood stream. Cats seem to eat better and to have slower progression of kidney failure if they receive potassium supplementation and this appears to be true even for cats with low normal potassium levels as well as cats with below normal levels.

Calcitriol: The active form of Vitamin D3 is calcitriol. Since Vitamin D levels are partially controlled by the kidneys they often fall in kidney failure. When this happens parathyroid hormone levels rise. This can cause depression, decreases in appetite and detrimental changes in bone structure. Supplementing calcitriol may help to reverse these problems. There is some controversy about this but most pet owners whose cats receive calcitriol believe it helps and in limited studies it does seem to control increases in parathyroid hormone levels which should be a benefit to the cat.

Blood pressure medications: Many cats with kidney failure will eventually develop hypertension (high blood pressure). There are slight benefits to the kidney when blood pressure rises just above normal but once the blood pressure becomes excessive the kidneys are damaged. The kidneys play a major role in the control of blood pressure so it is logical that this process would become deranged as kidney failure progresses. Monitoring blood pressure and controlling high blood pressure are important aspects of treatment for kidney failure in cats. Most veterinarians think that amlodipine (Norvasc Rx) works best for blood pressure control in cats but there is some evidence that angiotensin-converting enzyme inhibitors (ACE inhibitors) such as enalapril may be helpful in conserving kidney function so it may be helpful to use both types of blood pressure medications in some cats.

Gastrointestinal protectants: Most cats with kidney insufficiency will eventually have gastrointestinal irritation that is significant and interferes with appetite and comfort. Administering famotidine (Pepcid AC tm) or similar compounds seems to help a great deal with this.

Appetite stimulants: When cats are uncomfortable due to uremia associated with kidney failure they may fail to eat or may eat much less than normal. Appetite stimulants can be very helpful when this occurs. Cyprohepatidine ( Periactin Rx) and diazepam (Valium Rx) often help to restore appetite.

Kidney Transplant: Once it is clear that a cat is going to have progressive kidney damage it is reasonable to consider a kidney transplant. Success rates for this surgery are high enough to warrant considering it. Cost can be a major factor as the surgery is costly, the graft rejection medications are costly over time and it is necessary to adopt the cat who donated the kidney in most cases as they usually come from animal shelters with the express condition that they get a home in exchange for the kidney donation.

As you can see there is a large list of possible treatments for any cat affected by kidney disease. It would be hard to use all treatments in a particular cat as it would entail giving multiple medications orally as well as by injection in the case of the fluids. Doing all these things day in and day out to one cat would probably make the cat so resentful of care that it would defeat the purpose of extending his or her life. It is important to tailor the treatment effort to include the things most important to your cat and to add the other options in only as they become more necessary, in order to treat your cat effectively while preserving the option of increasing care for short periods of time when absolutely necessary.

If your cat has kidney failure and your vet hasn't mentioned all of these options you should remember that there are more things that can be done, if necessary and if you wish to. Remember that most cats with kidney failure are going to have a slowly progressive disease and that you can modify treatment efforts over time as necessary. Many cats who develop signs of kidney insufficiency during their middle age period will still live well into their geriatric years.

Dogs with Kidney Failure

Dogs with kidney failure are a different story. Once kidney failure becomes chronic in a dog the long term prognosis for dogs is usually much worse than for cats. Some dogs will live a year or more despite progressive kidney disease but the best long term prognosis for dogs occurs when acute kidney disease is recognized early and treated very aggressively and the disease is arrested completely. This changes the options considerably when a dog is diagnosed with kidney failure, compared to a cat.

Fluid therapy: It is really critical that dogs be treated aggressively with fluid therapy early in kidney disease, at least until a reasonably firm understanding of the cause of the kidney failure is reached. For dogs this usually means intravenous fluid therapy in large volumes. Over the years I have been corresponding with people online I think that one of the most consistent problems with veterinary care that I have seen is the unwillingness of either the pet owner or the veterinarian to administer adequate fluid therapy early in kidney disease in dogs. If your veterinarian is unwilling or unable to provide high volume fluid therapy for your dog when acute kidney failure is diagnosed it is important to ask for referral to a veterinary internal medicine specialist, a twenty-four hour intensive care facility or somewhere it will be possible to obtain this therapy.

Antibiotic therapy: In cats we rarely see bacterially induced kidney disease, although it can occur. In dogs we try to assume that leptospirosis might be present in almost all cases of acute kidney failure. It is best, at least in my opinion, to start antibiotic therapy with an antibiotic capable of killing leptospirosis until the disease can be ruled out with reasonable certainty.

Blood pressure medications: There is pretty good evidence in dogs that the use of enalapril can be beneficial for kidney disease even when high blood pressure isn't present -- so in dogs we often use this medication even in the absence of evidence of hypertension. It is even more important to use it when high blood pressure is present.

Gastrointestinal protectants: Dogs with uremia seem to have more gastrointestinal irritation than cats and so we use these medications more consistently than in cats. It is also easier to give dogs multiple medications if they have any appetite because it is usually easier to hide pills in treats successfully when dealing with dogs rather than cats.

Calcitriol: We don't use calcitriol as often in dogs as we do in cats but when we think that there may be a reasonable long term prognosis we do think it can be helpful.

Dietary changes: Dogs seem to benefit from dietary changes earlier and perhaps more strongly than cats. It is reasonable to switch to diets supportive of kidney function as soon as the immediate crisis is under control and the dog is back to eating reasonably well. Introducing diets meant for long term support of kidney function while the dog is uremic and feeling ill may predispose the dog to rejecting the diet. There is still some confusion about the best dietary approaches to chronic renal failure in both dogs and cats so do not be too alarmed if your vet has a different opinion or if I change my opinion of dietary care for kidney disease in the next issue of the VetInfo Digest!

Hyperadrenocortism - Cushing's Disease

I get a lot of questions about Cushing's disease. This is a hard disease to understand for many veterinary clients and giving information in outline form creates some risk of confusion. Don't forget that you can look back at the past issues of the VetInfo Digest in the subscriber area for more information. Some of the issues that contains information about hyperadrenocorticism are: http://www.vetinfo.com/subscriber/0899digest.html and http://www.vetinfo.com/subscriber/0303digest.html (in regards to testing for this disorder).

When to treat:

If the pet has symptoms that are creating problems in the household. We usually end up treating Cushing's disease when increased urination and increased drinking become a problem for pet owners.

If a pet has symptoms that are causing problems for the pet. Persistent skin infections, recurrent or difficult to treat bladder infections, excessive panting and muscular weakness can all occur with Cushing's disease.

If a pet has no symptoms or no worrisome symptoms but tests indicate that Cushing's disease is present I think it is optional to treat.

Testing for hyperadrenocorticism:

There are two screening tests for this condition, the low dose dexamethasone suppression test (LDDS) or the ACTH response test. There are advantages and disadvantages for both tests and it seems reasonable to start testing with either one. If the results aren't clear, running the other test might clarify things.

Once it is clear that Cushing's disease is present an additional test should be run to determine if the Cushing's disease is caused by pituitary tumors or adrenal gland tumors. A high dose dexamethasone suppression test is one way to do this. MRI exams and ultrasound exams can be used to look for indications of either pituitary gland or adrenal tumors, as well.

It is very important to test until it is reasonably clear whether the hyperadrenocorticism originates from pituitary problems or adrenal gland problems. Stopping short of this point could lead to treatment failure.

Treating hyperadrenocorticism:

For pituitary origin hyperadrenocorticism there are four therapies that can be considered:

1) Selegiline (Anipryl Rx, generics available)-- works in only 20% of dogs but can be very beneficial for this group of dogs, as it may be able to arrest the progression of the underlying disease. If the Cushing's disease isn't complicated by diabetes, persistent infections, pancreatitis or other conditions that high cortisone levels can influence it is reasonable to try 2 months of selegiline therapy to see if it will work.

2) Mitotane (Lysodren Rx) -- Mitotane has been the standard medical treatment for hyperadrenocorticism for some time. Its use must be monitored closely. In most cases it will be necessary to run ACTH response tests several times while attempting to regulate mitotane use. Mitotane is given on a variable schedule depending on need. Once a maintenance dosage has been acheived it is still necessary to monitor the patient periodically using ACTH response testing.

3) Trilostane ( Vetoryl Rx) -- trilostane is a newer medication for hyperadrenocorticism. It is intended for daily use. It is not approved in the U.S. but it is possible to purchase trilostane from compounding pharmacies and through experimental drug application to the FDA. It is necessary to run ACTH response tests to monitor treatment until it is clear that a maintenance dosage has been identified and then periodically to make sure that the dosage continues to be appropriate.

4) Transsphenoidal hypophysectomy -- Surgery to remove the tumor from the pituitary gland. At the present time I am only aware of two places claiming to have much success with this surgery, Auburn University in the U.S. and Utrecht University in the Netherlands. Personally, I think that I would pursue this option at this time, if I had a pet with hyperadrenocorticism who did not have other problems that made the long term prognosis unfavorable. It is unfortunate that there are so few places where this surgery is routinely performed as it is obviously not possible for everyone to consider this option due to the limited availability.

Treating Dogs with Adrenal Origin Hyperadrenocorticism:

There are two options for treating dogs with adrenal origin Cushing's disease. The first is surgical removal of the affected adrenal gland(s) and the second is medical treatment with mitotane.

Surgery is a high risk proposition for dogs with adrenal origin Cushing's disease. Estimates of mortality during surgery and in the post-operative period run as high as 50% in some reviews. Adrenal tumors spread relatively quickly to other organs and it is possible to successfully remove the adrenal gland but to miss metastasis of the tumor to surrounding organs, which makes the surgery an ineffective treatment when it happens.

Due to the complications associated with surgery there is an increasing tendency for veterinarians to treat adrenal gland tumors with aggressive use of mitotane. When dealing with adrenal tumors the goal of mitotane therapy is slightly different from when it is used for pituitary gland tumors. Mitotane is a chemotherapeutic agent capable of completely destroying the adrenal gland if not monitored closely when being used to control Cushing's disease. Thus the standard procedure for pituitary gland origin Cushing's disease is to use Mitotane to control the adrenal gland hypertrophy by killing off tissue a little at a time. This requires careful monitoring of the patient over time. When there is an adrenal gland tumor the goal is different. Mitotane is used to completely destroy the adrenal gland and any adrenal gland cancer that has spread to other organs, if possible. Taking this approach produces a patient with hypoadrenocorticism or Addison's disease. This disease requires lifelong use of medications to replace the natural adrenal gland steroids and some monitoring to make sure the replacement hormones are working appropriately. The survival rate using this approach appears to exceed that associated with surgery but not by a great deal. The patient is spared surgery, though. Before considering this approach it is important to recognize that patients with hypoadrenocorticism may require daily medications. Don't take this approach if you can't guarantee that you will be able to provide long term care without interruption!

Diabetes mellitus (Sugar diabetes)

Diabetes in dogs almost always requires insulin administration. Cats can sometimes be maintained for long periods of time using dietary changes and medical treatment, although it may be preferable to start treatment for diabetes with insulin in all cats and then to try to maintain the cat later without insulin if it looks like that might be possible.

There is absolutely no question in my mind that the best way to monitor pets with diabetes to aid in regulating insulin levels is for the veterinary client to learn to monitor blood sugar at home using a blood glucose meter. It appears that about 50% of veterinary clients can manage this task readily and most can manage it with encouragement from their vet and the vet's staff. Some vets are not yet ready to take on this task, though. If your vet is one of those who discourages clients from attempting home glucose monitoring I personally think that you ought to change vets, at least for the pet with diabetes, unless there is a really compelling reason to stay for reasons other than the diabetes treatment.

Purchasing one of the newer blood glucose meters that require very small blood samples is best. It can be hard at times to get blood from a pet and they tend to move around a lot during the blood drawing process, making it critical that whatever blood you can get can be utilized quickly. Spend a little extra to get a good glucose meter, such as the One Touch (tm) glucometers and it will pay off over the long run in ease of use.

Regulating insulin dosages and blood glucose levels requires a lot of communication between the veterinary client and the vet. It can be a frustrating process that can take months in some cases. There are a few patients who are just extremely difficult to regulate. Despite this most insulin regulation failures are the result of insufficient communication between the veterinarian and the client or insufficient effort on the part of either the vet or the client, or both. It is nearly always possible to regulate insulin with adequate effort on everyone's part.

Choosing the type of insulin to use can be confusing. We almost always start with human NPH insulin, either Humalin N (Rx) or Novalin NPH (Rx) because these insulins are widely available and seem to work well for us. It is important to try to stick with an insulin type once good regulation is achieved so it is helpful to use an insulin that is likely to be available when you need it. Some vets prefer PZI insulin and there is now an insulin approved for use in dogs ( Vetsulin Rx) that is pork based and may work more consistently for dogs since pork insulin is closer to dog insulin than the human products. In addition, glargine (Lantus Rx) seems to work better for some cats than other types of insulin. Since it is also a human product there is a good chance that it will be available at all times, as well. Don't change insulin types willy-nilly, but remember that there are alternatives if regulation is proving to be very difficult.

A blood glucose curve is a plot of blood sugar levels during the day. It is generally done by obtaining a blood glucose level at the time of the morning meal and every 2 to 4 hours afterwards for at least 12 to 16 hours. Plotting the blood glucose numbers on a chart allows visualization of when the level is too high, too low or just right. The pattern of rises and falls in blood glucose allow the veterinarian or the client to see if the problem is an overdose of insulin, an underdose of insulin or resistance to the effects of insulin. This is valuable information that is essential to really good regulation of insulin levels.

Even though I strongly believe in the value of blood glucose monitoring at home, it is possible to monitor sugar levels using urine testing when abolutely necessary. Monitoring urine levels doesn't work as well as monitoring blood sugar levels but is better than not monitoring at all for those who are challenged by drawing blood from their cat.

This is probably veterinary heresy but I treat pets with insulin when the owners are willing to give the insulin injections twice a day but unwilling to pay for additional lab testing or won't attempt getting blood or urine for testing at home. I am willing to do this because the pet is going to die much more quickly, in most cases, if insulin is not used. We explain how to monitor behaviors such as drinking, urinating, appetite and attitude to evaluate whether blood sugar is too low or too high and hope for the best. People get pretty good at recognizing signs of high and low blood sugar over time. If their pet makes it to a stable situation there is a good chance of long term survival as long as insulin continues to be provided. Sometimes, when there is early success, these folks start to believe their pet might make it and go ahead and purchase home glucose monitors or work with us in other ways to monitor their pet's diabetes.

Feeding Your Pet

I am always a little hesitant to get into the subject of pet foods and dietary requirements of pets. I always get a number of emails after writing anything about diet. There is more controversy over this than most aspects of medicine relating to pets and veterinarians are not trained nutritional specialists. Veterinarians do have two advantages of most veterinary clients when discussing dietary information, though. They have had at least a little training in nutrition and the scientific training they have received helps most of them evaluate information relating to diet more critically than many veterinary clients do.

One thing I feel absolutely compelled to point out early on in this discussion is a point of logic. If you were manufacturing a dog food and you wanted to do your best to ensure your future would you make an effort to ensure that your diet was nutritionally adequate and unlikely to cause pets to either become ill or to shorten their lifespan? After all, it is easier to keep existing customers than to find new ones. If my pet food helped pets live twice as long as normal, isn't it likely that I would get twice as much business from customers over time? The companies that have been around a while and who seem to be making an effort to produce good pet foods are almost certainly producing good foods. Whether they are the absolute optimal food for any particular pet is open to question but overall the major pet food companies make good quality pet foods. Most pets do well when fed these diets.

There are some companies who prefer to put their money into marketing instead of research and who siphon off some of the business from the bigger pet food companies. In addition, there will always be a market for cheaper pet foods for pet owners who care more about cost than quality. So not all pet foods are high quality and there are occasionally pet foods which cause harm. Sticking to name brand pet foods is a good idea.

Despite the fact that it seems obvious to me that pet food companies who intend to be around a long time do much better if they produce good quality diets there are always doubters among the clients at my veterinary practice and among subscribers to the VetInfo Digest. There are lots of folks who believe in various theories concerning dietary needs of pets, including people who think that each dog breed should have a diet that matches foods available where the breed originated, people who believe that food ingredients should be served raw, including meat and people who believe that dog food companies are secretly trying to poison dogs and cats by using cheap ingredients that increase profits but harm pets. So I'm going to make some brief efforts to state my opinion on some of the dietary controversies.

What is the best pet food for dogs and for cats?

No one knows. Absolutely no one. Anyone who tells you otherwise is either lying to you or lying to themselves. Pick a diet that is guaranteed to meet the AAFCO feed trial standards as a minimum. If you are making a diet at home pay for the advice of a veterinary nutritional specialist to evaluate the diet to make sure it meets the minimum needs of pets. We do know the minimum needs pretty well because pets get sick or die if these needs are not met. What we lack is a test or method of determining the best possible diet for a particular pet. There are just far too many variables for anyone to know the diet that will meet the needs of an individual pet to the optimum degree. It is OK to experiment a little to see if your dog or cat will do better on a different pet food or with home made foods if you prefer. Try to be objective about the results of these feeding trials, though.

How many times a day should I feed my dog or my cat?

There is good evidence that both dogs and cats can survive with no problems with once daily feeding. Dogs are particularly well adapted to once daily feeding, even though they seem to like being fed twice a day (or more). Cats tend to like to eat small meals frequently but this doesn't seem to be a dietary requirement, just their preferred feeding pattern. So feeding once a day is fine but there is no problem with feeding more often as long as the total amount fed in a day doesn't exceed the caloric requirements of your pet.

Are raw meat diets safe?

The proponents of raw food diets say yes. Most veterinary nutritional specialists, the Center for Disease Control and many veterinarians say no. There have been a few attempts to answer this question objectively using controlled studies and the results so far seem to indicate that these diets do not improve health. Since I know that I'm not able to tell you with certainty whether feeding raw meat won't be beneficial for your particular pet all I can do is point out the risks that you are taking when feeding raw meat:

Dogs and cats are both susceptible to E. coli and Salmonella food poisoning. There is a possibility that they have increased resistance to these bacteria compared to humans but there is still plenty of proof that they can and do get these diseases at times from ingesting raw meat. Dogs and cats can also acquire Toxoplasmosis and other parasitic diseases from ingesting raw meat.

People have developed food poisoning from handling raw meat while preparing raw pet food diets. This is the concern that the CDC has with these diets.

Proponents of raw meat diets frequently say that they do not see illness in their pets when fed raw meat diets. It is likely that this is true for a significant number of dogs and cats fed raw meat. The risk of food poisoning is not huge but the effects of food poisoning on the pets who do become ill or die are significant.

What is the best diet to make my pet lose weight?

My personal opinion on this question is that the best diet is often the one that you're already using. You just need to feed less of it.

Calorie control for dogs:

Measure the amount you are feeding your dog using real measuring cups if feeding dry food. If feeding canned food carefully estimate the amount of food you are actually feeding. Then feed less. If your dog is fat it is getting more calories than it needs even if you are feeding an amount of food that seems small to you.

Most people won't cut out treats for their dogs. So feed treats that have some nutritional benefit and not too many calories, like dog biscuits instead of pig ears, and remember that these treats are contributing to the total daily calories so you have to subtract a little more from the daily dog food intake. Don' feed more than 10% of the total daily calories in treats that aren't nutritionally balanced.

Calorie control for cats:

Cats can not be calorie restricted to the extent that dogs can but a simple guideline for dieting cats is to feed one 5.5 to 6 ounce can of cat food per day and nothing else. This will meet the minimal caloric requirements of almost all cats while restricting calories enough that weight loss will usually occur.

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