• 24 APR 14
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    The Failing Kidney

    The Failing Kidney

    Failing kidneys (renal failure) is a common disorder affecting the older cat especially and occasionally also the young. In fact, it is one of the most common causes of death of older cats.

    The normal function of the kidneys is to excrete waste products, maintain normal water and electrolyte balance in the body and to produce certain hormones. Kidney failure occurs when these functions can no longer be maintained at the normal level. The kidney is made up of hundreds of thousands of little individual filtration units (called nephrons) that all work together. These units are so effective that two-thirds of them must become damaged before a noticeable effect is seen and kidney failure ensues. It is this surplus effect that allows humans to donate one kidney and still lead a normal life. It is also this surplus effect that makes early detection of chronic kidney disease very difficult.

    Kidney failure can occur suddenly (acute renal failure) or slowly and over a long period of time (chronic renal failure). Acute renal failure may be caused by infections, trauma, dehydration, toxins, certain medications, shock and many other causes. If treated early and aggressively, acute renal failure is usually reversible and full recovery is possible. Chronic renal failure, however, occurs over a long period of time and the initiating cause can usually not be identified. Chronic renal failure can also usually not be cured but its effects can be controlled or managed so that an affected cat may survive for a long time. Cats may even be born with abnormal kidneys and still live to a ripe old age.

    The symptoms and signs of chronic renal failure may initially be subtle and escape detection. The most common initial signs are increased volumes of drinking and the passing of more urine more often. As the condition progresses, other common signs are weight loss, inappetence, vomiting, diarrhoea, poor coat condition, anaemia, ulcers in the mouth or on the tongue, and ultimately weakness and death.

    Renal failure is diagnosed through laboratory evaluation of blood and urine samples. The level of certain body toxins that are usually excreted by the kidneys is measured in the blood. With kidney failure these toxin concentrations increase. The blood urea and creatinine concentrations are most commonly measured to detect renal failure. While the creatinine concentration is a more accurate indicator of kidney function, it can only be determined in a laboratory. The urea concentration, on the other hand, can be determined in your veterinarian’s consulting room but is not as accurate an indicator. Urine samples should ideally be evaluated at the same time. Other electrolyte abnormalities and anaemia may give further support to the diagnosis. Your veterinarian may also be able to palpate very small or irregular kidneys. Other tests such a sonar examination and X-rays may give further information and help to determine the cause and the prognosis.

    While chronic renal failure cannot be cured, good quality of life can be obtained through simple measures. Diet therapy is most important and protein, phosphorus and salt intake should be limited. Very good commercial diets are available to achieve this. Dehydration should be avoided at all costs. Antacids and phosphate binding medication is often used and may make a major difference. Anabolic steroids may stimulate the appetite and counter anaemia. Anti-nausea medication is used when necessary. ACE-inhibiting drugs are routinely prescribed to these patients. While kidney transplantation has become readily available in the United States, it is not yet performed in South Africa. It is important to remember that a cat with chronic renal failure can live a good quality life for a long period of time, with some assistance and simple management.

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