Chronic renal failure (CRF) is a common cause of illness in older cats. Unlike some other organs such as the liver, damage to the kidneys cannot be repaired. Signs of renal disease are usually seen once at least 70-75% of the renal tissue has been irreversibly damaged and, once established, CRF is generally a naturally progressive condition. The rate of progression of disease can vary hugely from cat to cat. There is no cure for CRF and in people with this condition, dialysis treatment followed by renal transplantation are the main options. Neither of these treatments are currently available in the UK, although it is possible to improve the quality of life of affected cats by employing a variety of medical treatments tailored according to the individual’s needs. In recent years many treatment advances have been made and there are now more options available to owners wishing to care for their cats with CRF. Before discussing these treatments in detail, it is important to consider what normal kidney function is and therefore the range of problems that cats with CRF may have.
In normal cats, the kidneys play many vital roles which include:
Elimination of waste products, drugs and toxins from the body via the urine
Regulation of the body’s acidity, electrolyte levels (calcium, sphynx cats for sale phosphate, potassium, sodium and chloride) and water balance
Production of hormones such as erythropoeitin (required to stimulate production of red blood cells by the bone marrow) and renin (important in controlling water and salt balance)
Activation of vitamin D (important in control of blood calcium and phosphate levels)
Regulation of blood pressure
Signs of CRF develop when two thirds to three quarters of renal function has been lost. Cats with CRF are vulnerable to problems including:
Accumulation of protein breakdown products (including urea and creatinine which can be measured in blood samples) which is associated with clinical signs of illness (e.g. nausea, vomiting, loss of appetite)
Acidosis (increased blood acidity)
Anaemia (partly due to lack of production of erythropoeitin)
High blood pressure (systemic hypertension)
CRF cats often show non-specific signs of ill health such as a variable or poor appetite, weight loss, depression and sickness. An increased thirst is seen in about one third of cats with CRF although this clinical sign can also be seen with various other conditions common in middle aged and elderly cats such as hyperthyroidism and diabetes mellitus (‘sugar diabetes’). Diagnosis of CRF therefore requires collection of blood and urine samples for analysis. Most commonly a diagnosis is made following identification of azotaemia (accumulation of the protein breakdown products creatinine and urea in the blood) and loss of urine concentrating ability (i.e. the urine is more dilute than it should be). Further tests may be required in some cats to identify the cause of the renal disease. For example ultrasound examination of the kidneys is usually a straightforward technique for identification of polycystic kidney disease (PKD).
Management of cats with CRF involves a range of treatments tailored according to the individual’s needs.
What is the ideal diet for cats with kidney problems?
It is common to prescribe specific dietary therapy since this has been shown to improve the quality of life and survival of cats with CRF and may reduce the rate of progression of disease. Renal diets typically have restricted levels of high quality protein which limits the amount of protein breakdown waste products for the ailing kidneys to excrete. Levels of phosphate are also restricted since cats with CRF have a tendency to retain excess amounts of this in the body which can contribute to their feeling unwell. Renal diets have increased amounts of potassium and B vitamins which CRF cats are vulnerable to losing in their urine and increased numbers of calories which helps CRF cats with a poor appetite to maintain a normal body weight. Renal diets usually have lower levels of sodium in them which may help to reduce the risk of high blood pressure developing.
It is possible to prepare home cooked diets for cats with CRF and veterinary recipes are available for this purpose. Most owners do not elect for home cooking protocols as this is very time consuming and therefore not a practical option in most cases.
Cats with CRF often have a poor appetite and this can be exacerbated by offering special kidney diets which may not appeal to the cat. In some cases, the use of appetite stimulants such as the anti-histamine cyproheptidine (trade name Periactin) or anabolic steroids can be helpful in stimulating an adequate appetite. More recently some vets have been treating cats with persistently poor appetites by placing a feeding tube into the stomach. Feeding tubes can be placed into the stomach using endoscopy and are referred to as PEG tubes when this is done (percutaneous endoscopically placed gastrostomy tube). Although an anaesthetic and short period of post-operative hospitalisation is required to place the tube, once in place these can be used for prolonged periods to administer food, liquids and medicines to the cat.