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Kidney Disease in Dogs


Introduction

My interest in kidney disease stems from being involved with a breed, the Chinese Shar-Pei, that is prone to genetic kidney disease (renal amyloidosis), and belonging to a family that also has genetic kidney problems (my grandfather, father, uncle and sister all have had Polycystic Kidney Disease).

I have compiled information here on diet, supplements, and medical treatments for dogs with some degree of kidney disease. One of my main goals is to provide alternatives to feeding your dog k/d, which I believe is inappropriate for dogs with early-stage kidney disease. It is also a problem if your dog does not want to eat it, as many dogs do not.

Start by reading the information below on the SDMA Test and Early Kidney Insufficiency, Understanding Protein, and Understanding Phosphorus.

The next section is about the Tests Used to Diagnose Kidney Disease. This information will help you to understand your dog's diagnosis, and decide whether additional tests might be advisable. It is important to know the severity of your dog's problem to best understand how to treat it, and it can also be meaningful to find the cause of the problem, especially in younger dogs, who may be suffering from Acute Renal Failure (ARF) rather than Chronic Renal Failure (CRF).

Next is Diet for Dogs with Kidney Disease. This section will not provide specific diets, but will give you the information you need to create your own diet that is right for your dog.

Is Feeding a Low Protein Diet Necessary or Desirable? provides links to and excerpts from a number of different articles and studies that show that feeding a low protein diet will not prolong your dog's life or slow the progression of the disease.

A Table is provided that lists nutritional values for a number of different foods you may want to feed.

Sample Daily Diet provides specific diet diet guidelines, and Nattie's diet talks about the diet and treatment that I used with my own dog.

I have also included information on Prescription Renal Diets and Non-Prescription Commercial Diets that may be able to be used for at least part of the diet for dogs with early-stage kidney disease.

Information on Supplements for dogs with kidney disease is also provided.

Last is information on Medical Treatment, including the use of Sub-Q Fluids.

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SDMA Test and Early Kidney Insufficiency

IDEXX Laboratories introduced a new test, the SDMA, for detecting loss of kidney function in 2015. This test can detect reduced kidney function when creatinine, BUN (Urea), and urine specific gravity are all still normal. It will be included with standard blood chemistry tests.

Urine specific gravity decreases when about 2/3 of kidney function has been lost, followed by increases in creatinine and BUN (Urea) when about 75% of kidney function has been lost. Prior to that point, the kidneys are able to function adequately even though they are not operating at full efficiency. The SDMA test identifies kidney disease on average when there is 40% loss of function (25% loss is the minimum level at which this test can detect a problem). On average, SDMA increases above normal about ten months (range: 2-27 months) earlier than creatinine rises above the normal range. Note, however, that a steady rise in creatinine over time, even if still within the normal range, may also signal loss of kidney function.

Please remember that dogs, like people, need only half of one kidney (25% function) in order to maintain normal kidney function. That's why people can donate a kidney and remain perfectly healthy. If your dog's SDMA is elevated, that does not necessarily mean he has chronic kidney disease, or even that he will develop it in the future. There are other causes of elevated SDMA. There could be a genetic or congenital abnormality in the kidneys that is not progressive, or something may have happened in the past that affected the kidneys, such as an infection, that is no longer present. Even if the loss of function continues to progress, chronic kidney disease is usually slowly progressive, and your dog could live for many years, including living a normal life span and eventually dying of something else entirely. This is not a situation that calls for panic!

The question becomes, what do you do if you discover that your dog has elevated SDMA with normal or very mildly elevated creatinine?

Let me start by telling you what not to do: do not put your dog on a prescription kidney diet.

A reduced phosphorus diet is not needed or beneficial until creatinine rises above 2.0 mg/dL (180 umol/L) or fasted blood phosphorus level rises above 4.5 mg/dL (1.5 mmol/L). Because creatinine is affected by muscle mass, very thin dogs with little muscle may benefit from a reduced phosphorus diet when creatinine is lower than 2.0 mg/dL. If you are feeding a high-phosphorus diet, such as a raw diet that is high in bone, it makes sense to switch to a diet with more normal phosphorus levels. Note that foods approved for adult dogs (maintenance) usually have less phosphorus than those approved for puppies or for all life stages, which require higher phosphorus levels.

Note that for most accurate results, it's best if you fast your dog for at least 12 hours prior to the blood being drawn, with no food but free access (always!) to water. Otherwise, a recent meal may bump phosphorus levels up enough to cause concern. I usually try to take my dogs in for a blood test first thing in the morning, then feed breakfast right afterwards (you can also get away with feeding breakfast right before, if there's no time for the food to be digested before the blood is drawn).

When creatinine or phosphorus blood levels go above these limits, then it is best to feed a reduced phosphorus diet, though the degree of phosphorus restriction depends on how advanced the kidney disease is. Keep in mind that foods such as Hill's k/d are designed for dogs with late-stage kidney disease, and are inappropriate for dogs with early-stage disease. See Understanding Phosphorus below for more information.

A reduced protein diet is not needed or beneficial unless your dog's kidney values are very high and causing uremia, in which case reducing protein can help to control symptoms. Dogs with significant protein in their urine may also benefit from reduced, but not low, protein diets. See Understanding Protein below for more information.

If your dog has protein in the urine (proteinuria), that calls for additional diagnostics. The first thing to do is to rule out a urinary tract infection (UTI), which can cause proteinuria. Since about 20% of UTIs won't show up on a urinalysis alone, it's best to do a urine culture, particularly if your dog is showing any symptoms such as increased drinking and urination, accidents in the house, more frequent urination, painful urination, difficulty urinating, or blood in the urine. If protein in the urine persists after a UTI has been ruled out or successfully treated, a urine protein:creatinine (UPC) ratio should be done to quantify the amount of protein in the urine, which will help to determine what treatment is needed, as well as monitoring progression and response to treatment. Blood pressure should also be tested. See the following for more info:

Here is an overview of things to consider when you discover that your dog has elevated SDMA, taken from webinars given by IDEXX about their new test:

For more general information on kidney disease, see the IRIS guidelines or IRIS Pocket Guide, which define the stages of kidney disease as follows:

SDMA can be elevated for reasons other than kidney disease, or there may be an underlying cause, such as heart failure, that affects both the kidneys and SDMA levels. Pay attention to other test abnormalities and symptoms; don't assume kidney disease just because SDMA is elevated. See The SDMA Test In 2018: What The Results Mean - What The Results Don't Mean for an in-depth analysis by a veterinarian of other causes for elevated SDMA.

Remember that chronic kidney disease usually comes on slowly; if your dog is suddenly acting sick or kidney values elevate rapidly, look for causes of acute kidney failure, including leptospirosis, toxins (rat poison, antifreeze, dehydrated treats from China, very high doses of vitamin D, large amounts of grapes or raisins), certain medications (aminoglycoside antibiotics, tetracyclines, NSAIDs such as Rimadyl), and kidney infection (pyelonephritis), among other things. Addison's disease can also affect the kidneys. Addison's disease usually causes gastrointestinal upset that comes and goes over a long period of time. Acute kidney disease is more dangerous in the short term, but kidney function can improve substantially if the underlying cause can be found and treated. Some dogs return to normal over a few days or weeks, while others may be left with some long-term damage to the kidneys.

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Understanding Protein

Dietary protein does not cause kidney disease, nor does it speed progression of chronic kidney disease. Dogs with kidney disease who are fed high-protein diets live longer and have a better quality of life than dogs fed low-protein diets. There are only two situations where protein needs to be reduced:

  1. Feeding too much protein to a dog with advanced kidney disease can lead to uremia, a syndrome caused by very high creatinine and BUN (urea) levels that causes nausea, vomiting, loss of appetite, and lethargy. Reducing dietary protein can reduce uremia and help with these symptoms, even though it doesn't help the kidneys themselves.
  2. Protein-losing kidney diseases such as glomerulonephritis are often linked to inflammation or infection anywhere in the body. It is thought that feeding too much protein may lead to higher protein loss in the urine (proteinuria), which increases inflammation, which in turn can lead to more protein loss. In this case, a moderate reduction in protein may reduce proteinuria and decrease inflammation. A low-protein diet, including a prescription kidney diet, is not indicated, as this can lead to low blood albumin that can cause edema (excess fluid in the body). Proteinuria can be monitored using a urine protein:creatinine (UPC) ratio to determine what level of protein works best for your dog. See the section on proteinuria above for more information.

See the following for more information:

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Understanding Phosphorus

Dietary phosphorus does not cause kidney disease, and there is no benefit in reducing dietary phosphorus below normal levels when the kidneys are still able to process phosphorus adequately. Once blood creatinine levels rise above 2.0 mg/dL (180 umol/L), or less if the dog is very thin with little muscle, this indicates that the kidneys are starting to have trouble processing all the wastes they need to. Limiting dietary phosphorus at this point has been shown to slow progression of kidney disease and prolong life by preventing mineralization of organs due to unprocessed phosphorus.

The best measure to use is to monitor blood phosphorus levels. The goal is to keep blood phosphorus at no more than 4.5 mg/dL (1.5 mmol/L) after fasting for at least 12 hours (no food but always free access to water). Fasting before the blood test can be important in order to get an accurate reading of blood phosphorus levels, since these can rise from a recent meal. I recommend scheduling blood tests for first thing in the morning, then feeding breakfast right afterwards (you can also get away with feeding breakfast shortly before the blood is drawn, if there is not enough time for the food to be digested).

If you are feeding a high-phosphorus diet, such as a raw diet that is high in bone, it makes sense to switch to a diet with more normal phosphorus levels. Note that foods approved for adult dogs (maintenance) usually have less phosphorus than those approved for puppies or for all life stages, which require higher phosphorus levels.

When creatinine rises above 2.0 mg/dL or fasting blood phosphorus rises above 4.5 mg/dL, then it is time to start reducing dietary phosphorus, with the amount of reduction linked to how high the creatinine and blood phosphorus readings are. For early-stage kidney disease, a valid goal is about 60 mg phosphorus per kilogram of body weight (about 27 mg/lb) daily. You can find non-prescription foods with 0.6% phosphorus or less on a dry matter basis, or about 150 mg of phosphorus per 100 calories, that will meet this goal.

When kidney disease progresses (creatinine > 2.5 or blood phosphorus > 4.5), reduce dietary phosphorus further, to about 40 mg/kg (18 mg/lb). This will require either a homemade diet or a prescription commercial diet. The lowest amount of phosphorus that you should feed, to dogs with late-stage kidney disease, is about 22.5 mg/kg (10 mg/lb).

The goal is to maintain blood phosphorus levels below 4.5 mg/dL for dogs with early-stage kidney disease (creatinine up to 2.0), 5.0 for dogs with moderate-stage kidney disease (creatinine 2.1 - 5.0), and 6.0 for dogs with late-stage kidney disease (creatinine > 5.0). When blood phosphorus goes above the recommended level for the stage of kidney disease, phosphorus binders should also be added to the diet.

See the following for more information:

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Links to More Information

Diet Information

Web Sites with Current Information on Kidney Disease

Technical

Feline oriented

More Links

Glomerulonephritis

These sites are technical, but provide very good information:

Leptospirosis (Acute Renal Failure)

Email Groups

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I regret that I no longer have much time to respond to questions. See my Contact page for more information. My name is Mary Straus and you can email me at either or

   


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