Dogs and cats often develop kidney problems with age. Scarring of the kidneys causes failure to concentrate the urine. As a result, your pet will drink more. Blood or urine tests taken at this time will demonstrate kidney damage. This is called renal insufficiency or early renal failure (ERF). Pets in ERF are apparently perfectly healthy but the diagnosis of ERF is very significant:

RISKS ASSOCIATED WITH EARLY RENAL FAILURE

ERF patients are at risk if they become dehydrated or develop low blood pressure. In particular, care must be taken if pets develop diarrhoea or have to undergo surgery. Many drugs, such as commonly used painkillers, may exacerbate kidney problems if given in ERF.

ERF patients are also at risk of developing urinary tract infections that may make infect the kidneys and worsen the disease. Pets with ERF rarely show symptoms of cystitis. Infection is only diagnosed if the urine is analysed.

However, the greatest risk for ERF patients is that, unless the patient is properly managed, kidney function will deteriorate and the patient will develop chronic renal failure and become seriously ill.

PROGRESSION OF DISEASE

By the time the diagnosis is made, ERF pets have lost two thirds of their healthy kidney tissue. The remaining tissue has to work under high pressure (renal hyperfiltration). This causes scarring of the remaining healthy kidney. Renal hyperfiltration also causes loss of protein in the urine. This depletes the body’s protein stores and causes muscle wasting and weakness.

Patients with ERF often develop very high blood pressure. This exaggerates renal hyperfiltration and promotes kidney deterioration.

Renal hyperfiltration can be treated by feeding low protein/low salt diets, controlling blood pressure and by the administration of a class of heart drug called ACE inhibitors.

During ERF, the inability of the kidneys to excrete metabolic waste products causes phosphate levels in the blood stream to rise. To correct this the body secretes a hormone called PTH. Although PTH is a naturally occurring hormone, it is very toxic and can be thought of as the “Bad Guy” of kidney disease. High levels of PTH cause depression, lack of appetite, nausea and vomiting.

Pets in ERF often develop chronic kidney failure with severe signs of ill health. Fortunately, there are methods of preventing the progression of disease. If the appropriate steps are taken, a pet in ERF may be maintained in good health for many years.

KIDNEY DIETS - PTH levels can be kept low by feeding special low phosphate (kidney) diets. Unfortunately, it is not feasible to make your own home-cooked kidney diets from ingredients you may have available at home. Many kidney diets for dogs and cats are now available. If your pet will not eat a particular brand, they will often eat another kidney diet from a different manufacturer. Please ask the nursing staff about the most appropriate brand of food for your pet. No tit bits should be given and, if the pet does not eat the kidney diet, no other foods should be offered.

Kidney diets take two to three weeks to lower PTH levels and usually your pet’s appetite will improve greatly after this period of time. Cats placed on kidney diets live an average of 3 years after diagnosis and carry an extra kilo of bodyweight compared with ERF cats that are not phosphate restricted.

If the pet will not eat kidney diets, the vet can prescribe “Periactin”, a simple drug that prevents nausea and greatly stimulates the appetite. In an emergency situation, where an animal will not eat a kidney diet, it is possible to add phosphate-binding agents to the food such as the indigestion preparation “Alucaps”. The dose is half an Alcucap mixed thoroughly into each meal.

MONITORING

Commonly, we will measure a pet’s blood pressure at the time of diagnosis. Unfortunately, this can be a complicated business in cats and smaller dogs. If blood pressure is raised, drug therapy can be of assistance. We may prescribe ACE inhibitors after appropriate phosphate restriction has occurred.

PREVENTION OF DEHYDRATION