Kidney Disease Explained

Principal Natural Treatments: Natural diet, omega-3 fatty acids
Other Natural Treatments: Astragalus, burdock, dandelion leaf, Echinacea, garlic, Ginkgo biloba, gotu kola, hawthorn, marshmallow, B vitamins, glandular supplements

Kidney disease involves any insult to the kidneys. If the insult continues, the kidneys can experience failure. Kidney failure can be divided into either acute kidney failure or chronic kidney failure.

Acute kidney failure can occur in dogs and cats of any age, although most commonly younger pets are affected. Acute kidney failure can occur from a number of causes. Prerenal causes (not directly involving damage to the kidney) of acute kidney failure include low blood pressure, low blood volume, heart failure, and certain medications such as nonsteroidal anti-inflammatory medications and ACE inhibitors such as enalapril, a drug marketed as Enacard used for pets with heart disease. Renal causes (involving direct damage to the kidneys) of acute kidney failure include intrinsic kidney diseases, toxins that directly attack the kidneys (such as antifreeze poisoning or aminoglycoside antibiotics), cancer of the kidney, kidney trauma (kidney stones, direct trauma), congenital disorders (polycystic kidney disease, renal cortical hypoplasia), and infections (leptospirosis in dogs, feline infectious peritonitis in cats). Postrenal causes (involving a blockage of urine outflow from the kidneys or bladder) of acute kidney failure include bladder stones, urethral stones, bladder cancer, and feline lower urinary tract disease (including urinary tract obstruction that is most commonly seen in male cats).

Treatment of acute kidney failure involves intravenous fluid therapy (or periotoneal dialysis) to decrease the uremic toxins that accumulate in the blood, antibiotics if needed for infectious causes, antidotes for poisoning, and removal of any blockages or obstructions that may be causing the kidney failure. Many pets with acute kidney failure die despite intensive therapy. Those who recover are considered cured.

Chronic kidney failure is the most common form of kidney failure in dogs and cats, and is one of the major causes of illness and death in older dogs and cats. Several studies have shown that the mean ages of dogs and cats with kidney failure were 7.0 years for dogs and 7.5 years for cats. Most pets with chronic kidney failure are older than 10 years old, and the incidence increases with age.

The pathologic (microscopic) diagnosis of kidney failure in dogs and cats includes disorders such as glomerulonephritis, amyloidosis, tubulointerstitial nephritis, and occasionally, lymphoma cancer. Regardless of the actual microscopic diagnosis, the actual cause of chronic kidney failure in most pets is unknown. Initiating factors causing chronic kidney failure remain unclear in most cases, and much controversy has been raised in speculating exactly what causes older pets to develop kidney failure. According to one author, Dr. Donald Strombeck, in Home-Prepared Dog & Cat Diets (ISUP, 1999), the increased incidence of kidney disease may be related to feeding processed pet foods, as the incidence has increased since the increase in the popularity of these diets. Dr. Strombeck theorizes that increased levels of vitamins and minerals (especially vitamin D, calcium, and phosphorus) added to processed foods may, over time, damage the kidneys ultimately leading to kidney failure. However, while kidney failure is common in older pets, not every older pet eating processed food develops kidney failure. Other contributing factors seem to be involved as well. Feeding properly balanced homemade diets, and avoiding unnecessary use of chemicals, vaccinations, and infections are potential solutions to decrease the possibility of kidney failure. Dental infections, the most common infectious disorder in dogs and cats, are easily treated by regular dental cleanings, removing oral bacteria before it can travel throughout the body causing liver, heart, or kidney infections.

PRINCIPAL NATURAL TREATMENTS

Natural Diets

There are several dietary nutrients to consider altering in pets with kidney disease and kidney failure, including protein, phosphorus, sodium, potassium, and fatty acids.

Protein

Protein restriction is often recommended for pets with kidney disease and kidney failure. Dietary protein is broken down to acid products that are normally excreted by the kidneys. Diseased kidneys cannot excrete these acid products and other toxins as efficiently as normal kidneys. As these products accumulate in the blood, signs of uremia and kidney failure (excess thirst, excess urination, decreased appetite, foul breath, lethargy) occur. Amino acids containing sulfur, as well as extra phosphorus in the diet, contribute to the formation of these acid products and toxins. Excess phosphorus in the body, as occurs in pets with kidney failure, can combine with calcium-forming crystals. These crystals can precipitate into the kidneys and other organs, further contributing to terminal kidney and multiorgan failure. By reducing ingredients in the diet that contain sulfurous amino acids and phosphorus, we can promote kidney health and reduce kidney damage.

Animal sources of protein (meat) are high in sulfur-containing amino acids and phosphorus. Plant protein sources contain less sulfurous amino acids and phosphorus and also minerals such as potassium and magnesium that contribute to an alkaline urine, promoting kidney health. Proteins of high biological value that contain little phosphorus are preferred for pets with kidney disease and kidney failure.

Eggs contain the protein of the highest biological value and are often recommended for pets with kidney disease or kidney failure. However, eggs also contain sulfurous amino acids, which could contribute to acidosis. Egg protein can be safely fed to most pets with kidney disease without contributing to acidosis -- except in terminal kidney failure or if blood testing reveals acidosis.

While plant proteins do contain less sulfurous amino acids, the biological value of their proteins is less than egg protein so more protein would need to be fed if plant proteins were selected as the protein source for the diet. This extra protein would require more waste products to be excreted by already damaged kidneys, which is why egg protein is usually recommended for kidney diets. Tofu can be used as a compromise if the pet cannot tolerate egg protein.

Phosphorus

By decreasing meat in the diet, we also reduce phosphorus levels (which are often severely elevated in pets with kidney failure). Phosphorus may be more toxic than protein in pets with kidney failure. Whenever we decrease protein, we also decrease phosphorus. Phosphorus-binding agents, given orally, can be useful in pets with elevated blood phosphorus levels if the following diet, which is low in phosphorus, cannot maintain acceptable phosphorus levels.

Sodium

While high blood pressure (hypertension) is rare in pets, it can occur as a result of kidney failure in dogs and cats (and in cats with hyperthyroidism, which can occur concurrently with kidney failure). Most commercial diets have excessive levels of sodium to improve palatability and act as a preservative. Sodium restriction in the diets listed here can be a first line defense against hypertension.

Potassium

Kidney failure usually results in potassium loss through the failing kidneys, even if the blood potassium level is normal (blood levels of potassium do not reflect cellular levels). Unless increased potassium blood levels are detected (which can occur in some pets with kidney failure), extra potassium supplementation can be of benefit. Potassium chloride, a salt substitute, is recommended in the diets; other sources of potassium supplementation can be obtained through your veterinarian.

The following diets are starting points for feeding pets with kidney disease and kidney failure. Check with your veterinarian to determine the exact needs for your pet.

Diet for Dogs with Kidney Disease

Dogs with kidney disease may do well on the basic dog diet. If kidney failure is present, the diet is adapted to offer lower protein and phosphorus with increased potassium. High quality protein (1-2 hardboiled eggs) is used as the protein source; brown (or white) rice, or baked (or boiled) potato with skin (3 cups of either carbohydrate source) is added to the egg(s). Canola oil is added as per the basic diet. The diet provides approximately 600 kcal with 15-20 grams of protein and 18 grams of fat.

This diet provides approximately 300% potassium, 50% phosphorus, and 115% of the daily requirements for sodium. Extra potassium (potassium chloride or potassium supplement) can be used if needed; check with your veterinarian.

Fresh, raw or slightly steamed vegetables (carrots, broccoli, etc.) can be used as a top dressing for the diet for extra nutrition and variety and to help bind intestinal phosphorus (approximately 1/2 to 1 cup per recipe.) Most vegetables provide approximately 25 kcal per 1/2 cup.

Calcium carbonate or calcium lactate (which may bind phosphorus) is used rather than bonemeal to decrease the phosphorus levels;1 1/2 - 2 pills of either calcium source are added to the diet. If reduced phosphorus is not needed, 3 bonemeal tablets (10 grain or equivalent) or 3/4 teaspoon of bonemeal powder to supply calcium and phosphorus with a multi-vitamin mineral supplement using the label instructions is added. Alternatively, a natural product from Standard Process (Calcifood Wafers or Calcium Lactate) can he used (use 1 Calcifood Wafer or 2 Calcium Lactate tablets for each 2 bonemeal tablets.)

When possible, natural vitamins made from raw whole foods, rather than synthetic vitamins (although both can he used in combination) are preferred, as the natural vitamins also supply plant phytochemicals, enzymes, and other nutrients not found in chemically-synthesized vitamins. Catalyn from Standard Process can be used as the natural vitamin in this recipe, at a dose of 1 Catalyn per 25 pounds; Canine Plus (VetriScience) could also be used following label dosages. The nutrient composition of the diet will vary depending upon which ingredients are used. In general, the above recipe supplies the daily nutritional and calorie needs for a 20 pound dog. The actual amount to feed will vary based upon the pet's weight (feed less if weight gain, more if weight loss.)

Added supplements which can be beneficial include omega-3 fatty acids which may be helpful for pets with kidney disease. Check with your veterinarian for guidelines.


Diet for Cats with Kidney Disease

Cats with kidney disease may do well on the basic cat diet. If kidney failure is present, the diet is adapted to offer lower protein and phosphorus with increased potassium. High quality protein (1-2 hardboiled eggs) is used as the protein source (2-3 ounces of salmon or tuna, or 3-4 ounces of poultry or beef can be substituted.) Since cats do not require carbohydrates, none need be added, although adding 1/2 cup brown or white rice, or baked or boiled potato with skin is acceptable. Canola oil is added as per the basic diet. Taurine (100 mg) is also added. The diet provides approximately 300 kcal with 15 grams of protein and 14 grams of fat. This diet provides approximately 200% potassium, 45% phosphorus, and 160% of the daily requirements for sodium. Extra potassium (potassium chloride or potassium supplement) can be used if needed; check with your veterinarian.

Calcium carbonate or calcium lactate (which may bind phosphorus) is used rather than bonemeal to decrease the phosphorus levels; l 1/2 pills of either calcium source are added to the diet. If reduced phosphorus is not needed, 2-3 bone- meal tablets (10 grain or equivalent) or 3/4 teaspoon of bonemeal powder to supply calcium and phosphorus with a multi-vitamin mineral supplement using the label instructions is added. Alternatively, a natural product from Standard Process (Calcifood Wafers or Calcium Lactate) can be used (use 1 Calcifood Wafer or 2 Calcium Lactate tablets for each 2 bonemeal tablets.)

When possible, natural vitamins made from raw whole foods, rather than synthetic vitamins (although both can be used in combination) are preferred, as the natural vitamins also supply plant phytochemicals, enzymes, and other nutrients not found in chemically-synthesized vitamins. Catalyn from Standard Process can be used as the natural vitamin in this recipe, at a dose of 1 Catalyn per 10 pounds; NuCat Plus (VetriScience) could also be used following label dosages.

The nutrient composition of the diet will vary depending upon which ingredients are used. In general, the above recipe supplies the daily nutritional and calorie needs for a 10 pound cat. The actual amount to feed will vary based upon the pet's weight (feed less if weight gain, more if weight loss.)

Added supplements which can be beneficial include omega-3 fatty acids which may be helpful for pets with kidney disease. Check with your veterinarian for guidelines.

Omega-3 Fatty Acids

Omega-3 fatty acids can increase beneficial (anti-inflammatory) prostaglandins; these prostaglandins can reduce inflammation in the kidney and improve blood flow to the kidneys (a vasodilatory effect). Since omega-3 fatty acids can also lower blood cholesterol and triglycerides, this effect can also benefit pets with kidney disease as dogs and cats with induced kidney disease have elevated levels of blood cholesterol and triglycerides. (Studies have recommended a starting dose of 0.5-1.0 grams of omega-3 fatty acids/100 kcal of food/day.)

Omega-3 fatty acids -- eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) -- are derived from fish oils of coldwater fish (salmon, trout, or most commonly menhaden fish) and flaxseed. Omega-6 fatty acids -- linoleic acid (LA) and gamma-linolenic acid (GLA) -- are derived from the oils of seeds such as evening primrose, black currant, and borage. Often, fatty acids are added to the diet with other supplements to attain an additive effect.

Just how do the fatty acids work to help in controlling inflammation in pets? Cell membranes contain phospholipids. When membrane injury occurs, an enzyme acts on the phospholipids in the cell membranes to produce fatty acids, including arachidonic acid (an omega-6 fatty acid) and eicosapentaenoic acid (an omega-3 fatty acid). Further metabolism of the arachidonic acid and eicosapentaenoic acid by additional enzymes (the lipooxygenase and cyclooxygenase pathways) yields the production of chemicals called eicosanoids. The eicosanoids produced by metabolism of arachidonic acid are pro-inflammatory and cause inflammation, suppress the immune system, and cause platelets to aggregate and clot; the eicosanoids produced by metabolism of eicosapentaenoic acid are non-inflammatory, not immunosuppressive, and help inhibit platelets from clotting. (There is some overlap and the actual biochemical pathway is a bit more complicated than I have suggested here. For example, one of the by-products of omega-6 fatty acid metabolism is Prostaglandin E1, which is anti-inflammatory. This is one reason why some research has shown that using certain omega-6 fatty acids can also act to limit inflammation.)

Supplementation of the diet with omega-3 fatty acids works in this biochemical reaction. By providing extra amounts of these non-inflammatory compounds, we try to overwhelm the body with the production of non-inflammatory eicosanoids. Therefore, since the same enzymes metabolize both omega-3 and omega-6 fatty acids, and since metabolism of the omega-6 fatty acids tend to cause inflammation (with the exception of Prostaglandin E by metabolism of omega-6 as mentioned above) by supplying a large amount of omega-3 fatty acids, we favor the production of non-inflammatory chemicals.

Many disorders are due to overproduction of the eicosanoids responsible for producing inflammation, including kidney disease. While more research is needed, preliminary studies show that fatty acid supplementation may be beneficial in pets with kidney disease by regulating the eicosanoid production. Ongoing studies seem to support the belief that supplementation with omega-3 fatty acids may benefit pets with kidney disease or kidney failure.

In general, the products of omega-3 (specifically EPA) and one omega-6 fatty acid (DGLA) are less inflammatory than the products of arachidonic acid (another omega-6 fatty acid.) By providing the proper (anti-inflammatory) fatty acids, we can use fatty acids as an anti-inflammatory substance. However, since the products of omega-6 fatty acid metabolism (specifically arachidonic acid) are not the sole cause of the inflammation, fatty acid therapy is rarely effective as the sole therapy but is used as an adjunct therapy to achieve an additive effect.

Note: Flaxseed oil is a popular source of alphalinoleic acid (ALA), an omega-3 fatty acid that is ultimately converted to EPA and DHA. However, many species of pets (probably including dogs) and some people cannot convert ALA to these other more active non-inflammatory omega-3 fatty acids. In one study in people, flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. While flaxseed oil has been suggested as a less smelly substitute for fish oil, there is no evidence that it is effective when used for the same therapeutic purposes as fish oil. Therefore, supplementation with EPA and DHA is important, and this is the reason flaxseed oil is not recommended as the sole fatty acid supplement for pets. Flaxseed oil can be used to provide ALA and as a coat conditioner.


The Controversies

While many doctors use fatty acids for a variety of medical problems, there is considerable debate about the use of fatty acids. The debate concerns several areas:

What is the "best" dose to use in the treatment of pets? Most doctors use anywhere from 2 to 10 times the label dose. Research in the treatment of kidney disease indicates that the label dose is ineffective.

While current research shows that a starting dose of 0.5 to 1.0 grams of omega-3 fatty acids/100 kcal of food/day seems to work, more research may fine-tune this dose.

While the studies with omega-3 fatty acids show many potential health benefits, it is almost impossible to administer the large number of capsules needed to approximate the same dosage used in these studies. The best that owners can hope for at this time is to work with their veterinarians and try to increase, as best as possible, the amount of omega-3 fatty acids in the diet to try to get the recommended amount.

Is supplementation with fatty acid capsules or liquids the best approach, or is dietary manipulation preferred for the treatment of kidney disease? There are, in fact, diets constructed with extra omega-3 fatty acids. For owners who do not like giving their pets medication, or for those pets who don't take the fatty acid supplements easily, it might be wise to try some of these medically formulated diets (available from your pet's doctor) that contain the fatty acids. However, because these medicated diets may not be as natural as possible due to the inclusion of by-products and chemical preservatives, holistic pet owners may need to try other options. These diets, often prescribed as anti-inflammatory diets for pets with allergies, may be useful as a part of the therapy of kidney disease in pets.

Fish Oils

Since fish oils can easily oxidize and become rancid, some manufacturers add vitamin E to fish oil capsules and liquid products to keep the oil from spoiling (others remove oxygen from the capsule).

The bottom line is that there are many questions regarding the use of fatty acid therapy. More research is needed to determine the effectiveness of the fatty acids in the treatment of various medical problems, as well as the proper doses needed to achieve clinical results. Until definitive answers are obtained, you will need to work with your doctors (knowing the limitations of our current research) to determine the use of these supplements for your pet.

Fish oil appears to be safe. The most common side effect seen in people and pets is a fish odor to the breath or the skin.

Because fish oil has a mild "blood-thinning" effect, it should not be combined with powerful blood-thinning medications, such as Coumadin (warfarin) or heparin, except on a veterinarian's advice. Fish oil does not seem to cause bleeding problems when it is taken by itself at commonly recommended dosages. Also, fish oil does not appear to raise blood sugar levels in people or pets with diabetes.

Flaxseed Oil

Flaxseed oil is derived from the seeds of the flax plant and has been proposed as a less smelly alternative to fish oil. Flaxseed oil contains alpha-linolenic acid (ALA), an omega-3 fatty acid that is ultimately converted to EPA and DHA. In fact, flaxseed oil contains higher levels of omega-3 fatty acids (ALA) than fish oil. It also contains omega-6 fatty acids.

As mentioned, many species of pets (probably including dogs and cats) and some people cannot convert ALA to these other more active non-inflammatory omega-3 fatty acids. In one study in people, flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. While flaxseed oil has been suggested as a substitute for fish oil, there is no evidence that it is effective when used for the same therapeutic purposes as fish oil. Unlike the case for fish oil, there is little evidence that flaxseed oil is effective for any specific therapeutic purpose.

Therefore, supplementation with EPA and DHA is important, and this is the reason flaxseed oil is not recommended as the sole fatty acid supplement for pets. Flaxseed oil can be used to provide ALA and as a coat conditioner.

Flaxseed oil also does contain lignans, which are currently being studied for use in preventing cancer in people.

The essential fatty acids in flax can be damaged by exposure to heat, light, and oxygen (essentially, they become rancid). For this reason, you shouldn't cook with flaxseed oil. A good product should be sold in an opaque container, and the manufacturing process should keep the temperature under 100° F (some products are prepared by cold extraction methods). Some manufacturers combine the product with vitamin E because it helps prevent rancidity.

The best use of flaxseed oil is as a general nutritional supplement to provide essential fatty acids.

Flaxseed oil appears to be a safe nutritional supplement when used as recommended.

CONVENTIONAL THERAPY

Conventional therapies are supportive and include:

  • Fluid therapy: Given intravenously in critical cases (Subcutaneous fluids can be administered by owners at home following stabilization and for maintaining adequate hydration of the pet)
  • Antibiotics: Given when needed
  • Medications to decrease vomiting: Given when vomiting results from uremic toxins
  • Medications to stimulate red blood cell production: Given in cases of secondary anemia, which is seen in many pets with chronic kidney failure

Some cats with kidney failure are candidates for kidney transplantation; this is not routinely done in dogs. Continuous ambulatory peritoneal dialysis is another option for treating either acute or chronic kidney failure. However, due to potential complications, this technique is rarely used. Special diets low in protein, phosphorus, and sodium, with increased B vitamins and omega-3 fatty acids, are often recommended for dogs and cats with kidney failure. The use of these diets in older pets without kidney failure, but who simply show mildly elevated kidney enzymes on blood testing, is controversial and not now recommended by most veterinarians. Reducing protein concentration in geriatric pets is not recommended or needed and does not prevent kidney failure. Geriatric pets can benefit from reduced sodium and phosphorus levels but do not need protein restriction; many geriatric diets actually have increased levels of highly digestible, high-quality protein. Unlike acute kidney failure, chronic kidney failure cannot be cured as it results from chronic and permanent changes to aging kidneys.


Excerpt from The Natural Health Bible for Dogs and Cats: Kidney Disease used by permission of Prima Publications.
Copyright © 2001 by Shawn Messonnier, D.V.M. All rights reserved. Excerpt from The Natural Health Bible for Dogs & Cats, Prima Publishing, Roseville, CA.


 

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