Diet may not cure renal disease, but it can help the sick dog feel better.

As dogs age, they slow down - literally, figuratively and physiologically. One old dog may have arthritis in unstable hips, Another may have less tolerance for spicy snacks. Some suffer heart failure, others kidney disease. One part of the dog remains true, though. Our canines remain loving and loyal companions, and perhaps because of this bond we often nurse our older dogs along, trying to accommodate diseases that we can't cure - can barely influence - while eking out a little more time for our buddies.

Such is the way with chronic kidney disease; dogs with slowly failing kidneys may be managed with diet and drugs, not for a cure but for comfort, and perhaps a little more time.

The kidney is made of nephrons, tiny structures that filter blood, taking out substances that have outlived their usefulness or don't belong in the first place. These waste substances combine with water to form urine. Healthy dogs can regulate the amount of water lost, making urine more or less concentrated as needed.

When nephrons no longer work, substances aren't filtered from the blood and urine water isn't regulated.

Unfortunately, when nephrons no longer work, they can't be fixed. For humans, dialysis (that does the work of kidneys) and organ transplant help to save lives, but for a variety of reasons relating mostly to technology and economics, these alternatives remain experimental in dogs.

Occasionally, disease, poisons or devastating trauma (such as heat stroke) destroy nephrons. More often, nephrons are lost very slowly over time as dogs age. Because dogs have two kidneys and each kidney is made up of zillions of nephrons, with most of them held in reserve, many dogs live long happy lives, retaining enough nephrons for adequate kidney function. Others lose so many nephrons as they age that eventually the reserve is depleted and too few functional nephrons remain to do a satisfactory job. These dogs suffer progressive renal failure. The disease is usually one of old age, and there is not a shred of evidence to suggest that diet changes prior to this point affect this kind of renal failure.

Because renal failure is a progressive disease, signs exhibited by the dog, as well as laboratory test results, range from mild to severe. Common signs include increased frequencies of drinking and urination. Substances in blood that are normally removed by the kidneys now begin to accumulate. One such substance is a by-product of protein metabolism called blood urea nitrogen (BUN). Other substances commonly found in blood tests are creatinine and inorganic phosphate. High levels of BUN, creatinine and inorganic phosphorus suggest kidney disease.

As kidney failure progresses, the dog feels sick, loses its appetite and may vomit frequently. Also, its red blood cell count may decrease. However, because of the range of signs and lab tests, there is no consensus about when to institute treatment. If an aging Golden Retriever keeps her spark and

vitality, eats well and looks good, but has a slightly elevated serum creatinine, should she be treated for kidney disease?

Recent research has provided valuable insight into the management of dogs with renal failure. Before this work, we relied on information from other species and limited studies on dogs from the 1970's and early 80's, but there was neither comparative data on clinical management of cases nor information on the effectiveness of conventional dietary management.

Experimental studies from the University of Georgia and clinical trials from the veterinary school in Vienna, Austria, have provided new information. The research shows that moderate protein restriction works better than severe protein restriction, and that the combination of phosphorus and protein restriction works better than protein restriction alone. This information suggests dogs with renal failure will live happier, and perhaps longer, when fed diets containing restricted phosphorus and moderately restricted protein.

While moderate protein restriction may help, severe restriction leads to protein deficiency. Moreover, dogs love high-protein foods, and we now ask the patient to eat a diet moderately restricted in protein while already feeling nauseous. So diets need to be carefully formulated.

Several commercial pet foods are marketed for dogs with kidney failure. A few new products being tested in clinical trials reflect the latest research and are formulated with moderate protein and low phosphorus.

Loss of appetite is difficult to manage. The box contains a recipe for a homemade diet that has helped dogs with kidney failure. In my experience, this diet has been accepted by dogs that have been reluctant to eat low-protein commercial dog foods. The recipe uses fatty meats (such as fatty beef and lamb, tuna canned in oil and poultry with skin). By using calcium carbonate instead of bonemeal, the phosphorus level is lowered to 0.3 per cent. Calcium carbonate tablets are found in the vitamin and antacid section of supermarkets; tablets can be crushed.

This recipe provides about 800 calories, enough for a 22-pound dog for one day. If the recipe is increased or decreased, all proportions must be maintained. The diet can be refrigerated for a few days, or frozen.

Be sure to work with your veterinarian, for other treatments such as phosphate binders and fluid therapy may be needed.

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Rice, raw, long-grain 2/3 cup 140

Meat, fatty 1/3 cup 70

Liver 1/8 cup 30

Calcium carbonate 1/2 tsp. 3

Corn oil 1 tsp. 5

Iodized salt 1/2 tsp. 2

Place rice, salt, oil and calcium carbonate in 1 and 1/2 cups of boiling water. Cover and simmer 10 minutes. Add the meat and liver. Cover and continue to simmer another 10 minutes. Cool.