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Chronic Renal Disease in Cats

What is Chronic Renal Disease?
 
Chronic renal disease, or kidney disease, is one of the most common diseases of older cats. It is the result of several processes that cause damage to kidney function.
 
The kidneys are paired organs responsible for filtering the blood, removing our waste products and excreting them with our urine. They help regulate our hydration status, control our blood pressure and acid concentration, and maintain normal levels of ‘electrolytes’ in our system (such as calcium, phosphates, potassium, sodium etc). They are also important producers of certain hormones, including ‘erythropoietin’, which stimulates the bone marrow to produce red blood cells.
 
There is more than twice the number of filtering units needed by the kidneys, called nephrons, so they have a large ‘functional reserve’. This means they can compensate very effectively if disease damages some of the nephrons. However, this makes kidney disease very difficult to identify in the early stages. It is only when disease becomes quite advanced that the symptoms start to show. As the condition is progressive, symptoms are initially very subtle, but become more noticeable as the disease advances. Unfortunately, many of these signs are mistaken for ‘ageing’ processes, and so disease often progresses without early intervention or treatment.
 
What causes kidney disease?
Frequently we never identify the underlying cause of kidney disease, as biopsying the organs damages them further. However, the most common causes include developmental problems, tumours, infection and inflammation.
 
What are the symptoms?
Symptoms start to become obvious when the kidneys fail to carry out their usual functions. This usually occurs when there is a loss of approximately 66% of kidney function. Firstly, they lose the ability to conserve water, so there tends to be an increase in urination volume and thirst. Therefore, owners frequently notice their cat drinking more. As toxin levels rise in the system, where the kidneys are unable to filter adequately, cats may develop a poor appetite, halitosis (bad breath), ulcerations in the mouth and intermittent vomiting. They often become dehydrated, lose weight, develop a poor coat and become depressed. Electrolyte imbalances and acidosis develop as the kidneys fail to regulate normal levels. They may also suffer an increase in blood pressure (hypertension) and develop anaemia (low red blood cell count).
 
How is kidney disease diagnosed?
A thorough history from the owner is important to establish changes in thirst, appetite and demeanour. A full physical examination is needed to determine a decline in body condition. The kidney margins can be palpated for changes in size and shape. One of the most useful tests performed is a full analysis of the urine. Samples can be collected at home via non-absorbent litter kits (‘Katkor’); alternatively, cats can be ‘manually expressed’ by your vet, or urine collected via ‘cystocentesis’ (where a needle is passed through the body wall). The urinalysis will indicate how well the kidneys are concentrating; it may also identify protein in the urine, which suggests either the presence of kidney disease, or inflammatory conditions including infections.
 
Management of the Chronic Renal Disease Patient
 
As most causes of kidney disease are irreversible, treatment is aimed at limiting progression of disease, as well as identifying and managing its secondary effects.
 

1. Dietary Management

There are special diets available that have been formulated specifically for cats with kidney disease. They have been proven to markedly extend your cat’s survival and improve their quality of life. They work in by limiting the level of toxin accumulation in the blood, restricting phosphates and sodium and supplementing potassium and vitamin B. They are also extremely calorie dense, which is particularly helpful in maintaining body condition when cats lose their appetite.
 

2. Fluid Therapy

When the kidneys lose their ability to conserve water, dehydration commonly develops. This results in additional complications and further damages the kidneys. Some cats that are severely dehydrated may need to be hospitalised and given fluids via an intravenous drip. At home, fluid levels can be maintained via a number of different ways: feeding wet food rather than dry, mixing additional water with the wet food, offering numerous water bowls around the house, using ‘water fountains’, or tempting cats to drink with flavoured ‘broths’ such as prawn juice/fresh chicken stock (non-salty). Where cats may suffer recurrent bouts of dehydration, owners may be prepared to administer subcutaneous fluids at home. This is where special fluid is injected under the skin via a pre-placed veterinary port.
 

3. Anorexia

It is very common for cats to eat less with kidney disease. This is due to the build up of toxins that the kidneys fail to filter out of the system. These toxins are also responsible for causing nausea and vomiting. Offering smaller fresh meals, warming the food or feeding by hand can all encourage a cat to eat. Otherwise your vet may prescribe some medication to help improve their appetite and reduce vomiting.
 

4. Low Potassium and High Phosphates

Low levels of potassium in the system frequently develop due to a reduced appetite and increased loss via the urine. This results in lethargy, anorexia, reduced kidney function and may progress to generalised muscle weakness. There are dietary supplements which may be prescribed by your vet. Another common problem in kidney disease is the elevation of phosphates in the blood. This eventually causes widespread damage throughout the body and so it is essential to reduce phosphate concentrations. This is done by administering ‘phosphate binders’ which literally attach to the phosphate and encourage its elimination from the system.
 

5. Hypertension (high blood pressure)

It is thought that approximately 1 in 5 cats with kidney disease also have high blood pressure. As in humans, it has very serious consequences, including damage to the heart, eyes and brain, and exacerbation of existing kidney disease. Your cat’s blood pressure can be measured by your vet and appropriate treatment prescribed. Thereafter, regular blood pressure checks are recommended.
 

6. Urinary Tract Infections

Bacterial infections of the urinary tract are common and thought to be caused by the low concentration of urine produced in kidney disease. Diagnosis can be made by your vet from a simple urine analysis, and if indicated, antibiotics prescribed. Sometimes several weeks or months of treatment are necessary to eliminate these infections.
 
Further Check-Ups
 

Regular veterinary monitoring of your cat is essential to ensure secondary problems are identified early and treatment initiated as soon as possible. It is advised to check their urine and blood values at frequent intervals as well as measure their blood pressure and weight. These are used as indicators of improvement or deterioration. It is advised to discuss with your vet any concerns regarding your cat’s progress, as kidney disease and its effects are very individual. Therefore it is important each cat is given a monitoring program specific to them. The long-term outlook for cats with kidney disease is very variable, depending on the rate of progression and individual factors. Despite this, the treatment of kidney disease can be very rewarding, as early detection may give your cat a longer, healthier life.

 
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