Kidney Disease

To understand your cats kidney disease (renal disease), it is important to know some background information about the roles and functions of the kidneys.

The kidneys perform a number of essential roles necessary to sustain life.

The major ones are:

• Removal of waste products from the blood stream (urea and creatinine)
• Regulation of body water
• Balance of acid-base and electrolytes
• Production of erythropoietin, a hormone necessary for production of blood cells.

Each kidney contains about 200,000 nephrons, tiny units that perform those functions.  Kidney disease occurs when nephrons are destroyed.  If enough nephrons are destroyed that the kidneys can no longer perform their essential functions, kidney failure results.

Causes of Kidney Disease

There are numerous causes of chronic kidney disease in the cat and they can be very broadly classified into the following categories:

• Inflammation
• Infection
• Congenital or hereditary problems
• Toxins
• Cancer

Staging of Kidney Disease in Cats

An international staging system (IRIS) has been developed to categorise these different stages and can be found at http://www.iris-kidney.com/.  Cats' kidney disease can be staged based on their urine concentration and blood creatinine levels.

As nephrons are destroyed, the kidney becomes damaged, and it can’t perform normally.  The cat enters a stage of chronic renal insufficiency (Stage 1 IRIS) where they are still able to excrete waste products and maintain their weight, but will drink more water in order to do it. They may remain in this stage for several weeks to many years. They may be relatively healthy unless they get stressed or sick.

Eventually all cats will enter a stage of chronic renal failure (Stage 4 IRIS), which is the progression of disease which results in build up of waste products, dehydration, anaemia and eventually death.

There is also a new test called SDMA, offered by IDEXX labs, which can indicate the presence of kidney disease even before creatinine levels are high. A high SDMA level can prompt further diagnostics and increased monitoring of a cat, so kidney failure can be slowed down as much as possible.

Clinical signs of kidney failure

• Excessive drinking or urinating
• Weight loss
• Poor appetite
• Lethargy
• Vomiting
• Bad breath and mouth ulceration
• Unkempt or dull fur coat

Diagnosis

The most common way of diagnosing kidney disease is with blood and urine tests. Unfortunately, demonstrating a high level of waste products (urea/creatinine) in the blood tells us that the kidneys are not working properly, but it does not tell us what has caused the initial problem. Additional tests are often needed and may include:

• Urinalysis, where we look at urine concentration, and the presence of glucose, protein, blood, bacteria, crystals and cells in the urine
• Urine culture and sensitivity if infection is suspected
• Abdominal ultrasound
• Abdominal X-ray
• Needle aspirates or biopsies.  This is often done under ultrasound guidance if the kidneys are enlarged.
• Other tests, such as excretion tests, protein:creatinine ratios, etc

It is important to identify the cause as many diseases are treatable. In many cases it is impossible to identify the underlying cause without the use of these additional tests.

Treatment

The treatment for kidney disease will be different for every cat, depending on the cause and severity of the disease.

These include:

• Fluid therapy (intravenous or subcutaneous)
• Dietary protein restriction
• Dietary phosphorus restriction
• Controlling high blood pressure
• Iron and specific vitamins
• Appetite stimulants
• Erythropoietin
• Other specific treatments depending on the cause of kidney disease

If your cat has been diagnosed with chronic renal insufficiency, they should see a veterinarian every 3-6 months in order to record her body weight, get blood and urine samples and measure her blood pressure. This careful monitoring allows the vet to change her treatment if it becomes necessary.

The treatment for cats with chronic kidney failure will depend on many factors and may change as the disease progresses. Most cats will be treated with special diets, vitamins, iron, appetite stimulants, subcutaneous fluids and, if anaemic, will receive erythropoietin injections.

Outcome for Cats with Chronic Renal Failure

With early diagnosis and appropriate therapy, cats may live for years with chronic renal failure. It is impossible to give an accurate prognosis or life expectancy as there is a lot of variation between individual cats and the type of kidney disease present.

When is it time?

Chronic renal failure is usually a progressive condition. Our aim is to slow the progression as much as possible and maintain a good quality of life for your cat.

As the disease progresses, your cat will get weaker and sicker, and they will eventually die.  This is a very emotional time and careful assessment of your cat’s condition needs to be made.

As a general rule, once your cat loses his appetite despite our therapy, we will recommend that they should be put to sleep. The “right time” will be very different for every cat and for every owner. We will always be available to discuss your situation and do our best to make things as comfortable as possible for you and your cat.