Ron Hines DVM PhD 5/4/06

Every species of Animal has its weakest link. In us, it is often our hearts. Dogs, cats and ferrets do not suffer from the types of heart diseases we do. Instead, their kidneys often loose there ability to filter their blood and cleanse their body as time goes by. Kidneys are composed of millions of tiny filters called glomeruli. As blood passes through these filters, the waste products of protein metabolism are collected and excreted into the urine and bladder. In addition to this, these filters regulate the amount of water and minerals (electrolytes) present in the body.

As a precaution, Nature has given us much more kidney filtering capacity than our bodies need. The wear and tear of time as well as specific diseases, infections and nutritional imbalances slowly clog and destroy these small filters (glomeruli). It is not until approximately eighty percent of the filters have been damaged that the level of waste products in the bloodstream begins to increase. When veterinarians suspect kidney damage, they assay the amount of two byproducts of protein metabolism in the blood. These byproducts are urea and creatinine – products that give the urine its yellowish color. Normal blood levels of urea (Blood Urea Nitrogen or B.U.N.) and creatinine in dogs are 8.7-30.5 mg/deciliter and 0.68-1.45 mg/deciliter. In cats, these numbers are 13.4-32.5 and 0.68-1.84 respectively and in ferrets they are 0-52 and 0-2.2 respectively. As kidney function wanes, these numbers begin to increase. This disease is referred to as chronic kidney disease, chronic renal failure, renal insufficiency, chronic uremia or chronic interstitial nephritis.

Many pets with blood urea nitrogen levels of 60 to 80 seem perfectly content and normal. But by the time two-thirds of the filters are lost and as creatinine levels approach double their normal values certain signs begin. First, the pet will begin to drink more water and urinate more. In this way, the body can still cleanse the blood with fewer functioning filters. Each remaining glomerulus filters increasing amounts of water from the blood and so doing makes up for declining filter numbers. For reasons not fully understood, the animal also begins to loose weight. As the disease progresses, the pet also becomes anemic and may develop ulcers of the mouth and digestive tract. Blood phosphorus and potassium increase and blood calcium decreases. They may vomit; develop diarrhea or have a strong breath odor. The pet’s appetite decreases and its body becomes more acidic. Blood pressure increases. When I palpate the abdomen of these pets, I can often feel small hard and irregular (scarred) kidneys. Problems are often sporadic with long periods of comparatively good health intervening. Some times, periods of sickness develop after stresses such as boarding, the addition of other pets, etc. During these periods of stress the pet may drink less than the amount that is necessary to keep the blood free of waste.

Treatment: kidney disease kidney renal dog cat
It is important that pets with kidney disease have water available at all times. Because they need to drink very frequently. When symptoms occur, your veterinarian may give the pet extra fluids intravenously or subcutaneously. They may also administer a group of medicines called diuretics to increase urine flow. With these treatments, your pet can regain its metabolic balance. Human beings in this situation begin kidney dialysis to flush wastes from their body. Your veterinarian may accomplish the same thing by giving massive amounts of fluid under the pet’s skin. This fluid is soon urinated, carrying away nitrogenous waste as it goes. We also attempt to lessen the workload on the remaining kidney tissue by decreasing the amount of protein-waste that it must process. To do this, we place the pet on a special low protein diet (Hill's k/d, CNM's n/f brand, etc.).. These diets derive more of their energy from fats and carbohydrates so that they do not tax the kidneys. These diets are also low in phosphorus. Sometimes we place the animals on anabolic steroids and B-vitamins to encourage red blood cell production and appetite. Pets may receive the hormone, erythropoietin which also encourages red cell production. Aluminum hydroxide antacids help control digestive disturbances and remove excess phosphorus from the intestine. Low salt diets help control blood pressure as do certain heart medications. Recent studies at John Hopkins University Hospital found that administering the antifungial drug, ketoconazole also slowed the progression of kidney disease in rats. Similar studies have shown that high doses of vitamin E, omegad-3 fatty acids and flax seed oil also slow kidney destruction. So although this is a progressive disease with no absolute cure, a lot can be done to improve your pet’s quality and length of life.

Diet:
A diet suitable for cats and dogs with certain lower urinary tract problems that produce bladder stones or crystals in an acid urine (struvite) consists of: 1.5 lb of cooked ground chuck beef, with the fat retained, 1/4 lb of cooked calf’s liver, one cup cooked rice or mashed potatoes , 1 teaspoon canola oil, 1 teaspoon of phosphorus-free calcium carbonate (crushed calcium lactate or calcium gluconate) or 8 "regular Tums" tablets, one quarter Centrum tablet, 100iu of vitamin E. Fifty-six-84 ml (2-3 ounces) of water can be added during cooking if the cat or dog prefers a moister food. The addition of a taurine tablet and the vitamin E from drug store is advisable in cats of all kinds. Taurine deficiencies can lead to heart problems. Vitamin E (alpha-tocopherol acetate is known to slow the aging process by scavenging free-radicals). Taurine deficiencies can lead to heart problems. Vitamin E (alpha-tocopherol acetate) is known to slow the aging process). Feed approximately 1/4-1/2 lb per ten pounds each day or the amount that maintains optimal body weight. This formula is designed to keep magnesium and phosphorus levels in the food to a minimum. In dogs, bladder stones can sometimes be dissolved using a diet low in protein (not under 15%) which has added salt or potassium chloride to increase water consumption. Most of these dogs need antibiotics as well. In cats with oxalate bladder crystals, the addition of potassium citrate (300mg/day) will sometimes cure the condition. When used in dogs to encourage oxalate crystals to dissolve, the dose is 300mg/10 pounds body weight to a maximum of 1,800mg/day mixed in the food or given as a flavored treat.

A diet suitable for dogs and cats with failing kidneys can be prepared at home by adding one-half cup of cooked ground chicken breast or two crushed large hard-boiled eggs (no shells) to four cups of mashed potatoes or four cups of boiled brown rice. 30ml (Two tablespoons) of Canola oil, one-quarter Centrum tablet, 100iu of vitamin E, and 500mg of absorbable Calcium from any human calcium supplement, which is free of phosphorus on the label. As with all home-prepared diets, the addition of a taurine tablet and the vitamin E from a drug store is advisable in cats of all kinds. Taurine deficiencies can lead to heart problems. Vitamin E (alpha-tocopherol acetate is known to slow the aging process by scavenging free-radicals). Garlic or onion powder can be used in moderation if the diet is fed to dogs. It must never be fed to cats. The amount prepared should feed a ten pound cat for two to three days, or a 25 pound dog for a day or two, depending on its activity level and metabolic rate.***
A second recipe, originally published by Hill’s Pet Foods, for renal failure in dogs but somewhat modified by me, consisted of ¼ pound ground regular beef (not chuck or round), 1 large hard-boiled egg, two cups of cooked white rice, three slices of white bread, and a teaspoon full of calcium carbonate. I would add a multivitamin with vitamin E to this recipe.
A second recipe, originally published by Hill’s Pet Foods, for renal failure in cats but somewhat modified by me for cats and ferrets, consists of one quarter pound of lightly cooked liver (retaining the fat or adding two tablespoons full, if none is present) two large hard-boiled eggs, one teaspoon-full of calcium carbonate, one tablespoon full of canola oil, and one quarter teaspoon full of Morton’s Nu-Salt (salt substitute). I would add a multivitamin with vitamin E to this recipe.

In any of the renal diets, the addition of soluable fiber may be helpful in controlling uremia. The theory is that the bacteria that ferment this fiber in the intestines utilize some of the excess urea in the pet’s blood stream.

Blood Pressure:

Many pets with chronic kidney disease have been found to also have elevated blood pressure. Elevated blood pressure leads to destruction of the filtering apparatus of the kidneys (the glomeruli). At the present time, not all general practices have the equipment required to measure blood pressure in dogs and cats. Systolic pressure in dogs and cats should not be over 160 milimeters of mercury. Diastolic pressure is rarely measured. When blood pressure has been documented to be abnormally high, I may put your dog on one of a group of medications called ACE inhibitors (angiotensin converting enzyme inhibitors) which increase the diameter of blood vessels and so lowers blood pressure.. The most common one used in the United States is enalapril (Enacard,Vasotec, Merial Corp.).The usual dosage for this condition is 0.125 to 0.25mg/lb once or twice a day. A possible side effect is lack of appetite or vomitting. My first choice in cats is amlodipine besylate(Istin®, Norvasc) , a calcium channel blocker. Approximately 0.625mg or one quarter of a 2.5mg tablet is typically given once daily. If the cat's blood pressure remains elevated the dose may be doubled or Forticor can be added.

Some vets also suggest aspirin to help prevent blood clots that sometimes occurs in the kidneys due to glomerulonephritis. The dose of aspirin for this purpose is 0.25-1.0 mg/lb once a day. Do not give aspirin to cats. If you live in Canada, Europe or the Far East, a similar drug to enalapril, vetmedin (pimobendan) may be prescribed. The usual dose is 0.1-0.3 mg/pound body weight per day. The same side effects as seen with Enacard may occur. Another ACE inhibitor used to lower blood pressure is Forticor (benazepril HCl, Lotensin, Novartis Animal Health Canada). The published dose is 0.125 - 0.25 mg/pound body weight given once a day or divided into two daily doses.

There have been isolated instances of enalapril paradoxically seeming to cause kidney damage in pets.So blood BUN and creatinine levels should be measured prior to enalapril use, 3-7 days after begining the drug and and periodically thereafter.

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