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 Chronic renal failure (CRF) is a leading cause of death in dogs and cats. Renal failure occurs when over 75% of the cells or nephrons in the kidneys cease to function. It can occur quickly, usually as a result of toxins, which is known as acute renal failure, or it can occur gradually over weeks to years, and is known as chronic renal failure.
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What are the signs of chronic renal failure?
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Since one of the main functions of the kidneys is to regulate water balance in the body, as the kidneys decrease in function, excess water is excreted from the body. The animal can compensate for this by drinking more water to prevent dehydration, so excessive thirst is commonly noted as an early sign of CRF. Gradual weight loss is common.
The signs of chronic renal failure are usually non-specific, and include loss of appetite, weight loss, vomiting, depression, diarrhoea and dehydration. Ulcers can form in the mouth that leads to halitosis, and a painful mouth.
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How is chronic renal failure diagnosed?
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CRF is suspected with a history of excessive thirst and weight loss in an older cat or dog. Physical examination can reveal dehydration and small, irregular kidneys. Blood tests are performed to measure levels of specific substances in the blood, especially BUN (blood urea nitrogen) and creatinine, as well as electrolytes and red and white blood cells.
A urinalysis is important for detecting abnormalities in your pet’s ability to concentrate it’s urine – if your pet is dehydrated, he should have a concentrated urine as the kidneys attempt to conserve water in the body, but in CRF the urine is inappropriately dilute. Protein in the urine is measured, and any sediment is examined.
However, kidney enzymes only become elevated once significant kidney damage has occurred. There is a new urine test for both cats and dogs that has been developed to detect the presence of very small amounts of albumin in the urine. The presence of albumin in the urine is an indicator of damage associated with renal failure and/or other underlying conditions causing albumin to leak into the urine. This test will provide an early diagnosis of kidney damage long before BUN and Creatinine become elevated.
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Is chronic renal failure treatable?
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Unfortunately, it is usually not possible for renal function to improve in cats and dogs with CRF, since the nephrons are irreversibly damaged. Treatment is aimed at reducing the workload on the kidneys, and therefore reducing the signs associated with the disorder, as well as slowing the progression of the problem. Success of treatment depends on the number of functioning nephrons remaining, and this cannot be predicted.
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What treatment is available for chronic renal failure?
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Fluid therapy is the cornerstone of treatment for dehydration. Fluids are given intravenously in hospital. Other changes detected on blood tests are corrected, such as potassium losses, or excessive phosphorus. High blood pressure can occur with renal failure, and drugs may be required to address this problem. Vomiting may need to be treated.
Since many of the clinical signs related to CRF are associated with the accumulation of toxic protein catabolites and failure to excrete phosphorus, the emphasis in dietary therapy is on modification of the phosphorus and protein contents of the diet. Studies show that dietary phosphorus and protein restriction can slow the progression of renal failure and therefore increase survival time in cats. There are, however, potential problems with excessive protein restriction, which can result in protein malnutrition.
The protein requirements of cats in CRF have not been established but it is likely that they may be quite similar or even higher than those of the healthy animal. It is important, therefore, that high quality protein sources are used in the formulation of restricted protein diets to minimise the risks of essential amino acid deficiency.
It is not clear whether dietary protein restriction impacts on the progression of renal failure in cats. Current recommendations are that all cats with high urea, creatinine and phosphorus (that persist following rehydration) should be fed diets which are restricted in phosphorus and moderately restricted in protein, even when they are not showing signs of illness.
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How is my pet with CRF monitored?
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Regular check-ups are recommended to monitor body weight, and to ascertain the wellbeing of your pet. Blood and urine tests monitor whether your pet is responding well to treatment, or if the disorder is progressing. It is difficult to predict how an individual will respond – some can be maintained for years, whereas for others, the low level of kidney function remaining means that a return to health is not possible.
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Editor: Dr Julia Adams BVSc
Contributor: Dr Rebecca Bragg BVSc
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