Chronic Kidney Disease

Chronic Kidney Disease (CKD) is the name now used to refer to kidney failure (or chronic kidney failure) in cats.

What is the normal role of the kidneys?

Like all mammals, cats have two kidneys located in the abdomen, which perform the following important roles:

Blood is constantly filtered through the kidneys to remove the toxic waste products of the body’s metabolism. Urine is produced in this process. The kidneys also concentrate the urine by returning water to the body, preventing dehydration.

What are the signs of CKD?

Symptoms may include:

• Weight loss

• Poor appetite (inappetence)

• Lethargy

• Increased thirst (polydipsia)

• Increased urination (polyuria)

• Poor coat quality

• Vomiting

• Bad-smelling breath (halitosis)

• Weakness

How is CKD diagnosed?

A diagnosis of CKD is usually made by collection of blood and urine samples.

Three substances in the blood – urea, creatinine and SDMA (symmetric dimethylarginine)– are commonly elevated, and the urine is poorly-concentrated.

Sometimes other investigations such as X-rays, ultrasound or even biopsies may be needed.

How is CKD managed?

If a specific cause for the CKD is identified (eg, bacterial infection of the kidneys), treatment may be possible to arrest the progression of the disease.

In most cases though, treatment is symptomatic and supportive.

Some cats may require initial intravenous fluid therapy to correct dehydration and electrolyte abnormalities, but once stable, treatment is aimed at supporting kidney function and minimising the complications of CKD.

Optimal management of kidney disease usually requires monitoring at regular intervals to follow the progression of the disease and identify treatable complications as they arise. At RVC, we use the IRIS* Renal Staging Guidelines.

Factors monitored under this system are:

• Serum Creatinine and SDMA – these levels place the cat in Stages 1-4 of CKD

• Blood pressure

• Urine protein-creatinine ratio – a measure of protein loss through the kidneys

• Red blood cell count

• Serum potassium

• Serum phosphate

Dietary management is critical in cats with CKD, and there are three main aspects to this:

Other dietary measures

Other aspects of the diet may also have an important role to play in helping manage cats with CKD. These include the addition of anti-oxidants to try to protect the kidneys against further damage, essential fatty acids to help maintain blood flow through the kidneys and reduce inflammation, added potassium to prevent hypokalaemia (low blood potassium), and added bicarbonate (or similar) to help prevent acidosis (a buildup of acid in the body which can also occur in CKD).

All these measures have a role to play in keeping cats with CKD as healthy as possible for as long as possible. Because of the exacting nutritional demands in cats with CKD, feeding a specific veterinary therapeutic diet designed to manage all these aspects is strongly recommended. These diets are only available through your vet, and have a vital role to play in managing the disease.

Managing the change to a new diet

Cats will often develop a strong preference for particular diets, and low-protein diets tend to be less palatable. This means that changing cats with CKD to an appropriate therapeutic diet can take time.

These tips may help:

• Always make a change in diet gradual - over a few weeks if your cat is quite fussy

• Start by mixing a very small amount of the new food with your cat’s old food, and make sure it is well mixed

• Very slowly increase the proportion of the new food

• Warming the food to body temperature (around 30C) may help increase the palatability

• Sprinkling a little of the probiotic product Fortiflora onto the food may enhance the palatability

If cats absolutely refuse to eat any of a new diet, it is important that they eat something, so keep offering their old diet in this situation and contact your vet for further advice. An appetite-stimulant may help.

Potassium supplementation

Some cats with CKD develop low blood potassium levels. This can cause muscle weakness, can contribute to inappetence, and itself can worsen CKD. Where the renal diet is inadequately maintaining potassium levels, additional potassium supplementation may be needed.

Controlling blood pressure

Cats with CKD are at risk of developing high blood pressure (hypertension). This can have a number of damaging effects, including blindness and worsening of the CKD. Blood pressure should ideally be monitored in all cats with CKD and where hypertension is found it should be treated.

Phosphate binders

If blood phosphate concentrations remain high despite being on a low-phosphate diet, further treatment with drugs known as ‘phosphate binders’ to reduce the amount of phosphate absorbed from the intestine may also be needed.

Treatment of nausea and vomiting

In advanced CKD, nausea can cause inappetence and significantly affect the quality of life. Treatments which block nausea may help your cat feel better and improve appetite.

Telmisartin and “ACE-Inhibitors”

These drugs are vasodilators (dilate blood vessels) and help to support blood flow through the kidneys. They may help to lower blood pressure in cats, and also reduce protein loss through the kidneys.

Could my cat have a kidney transplant?

These are not currently available in NZ. Please be reassured they are not always successful and do not necessarily increase the cat’s life expectancy more than good medical supportive care.

What is the prognosis for cats with CKD?

Unfortunately, CKD cannot be reversed and is progressive over time. It will eventually lead to the need for euthanasia. However, the rate of progression of kidney disease varies considerably between individuals and appropriate support and treatment can both increase the quality of life of affected cats and slow down the progression of the disease.

How should I manage future visits to the vet?

Monitoring of your cat’s condition will occur monthly, 3-monthly or 6-monthly, depending on the stage of CKD (you will have input into this).

We wish for repeat visits to the vet clinic to be as stressfree for your cat and yourself as possible.

If your cat appears to suffer stress from car-rides or vet visits, we can dispense a Gabapentin capsule to be given an hour or two before the visit. This can make him/her calmer, without affecting test results. In fact, the results may be more useful, especially blood pressure readings.

Please arrive at least 15 minutes before your appointment time, so that your cat can recover from the car-ride and “acclimatise” to the clinic environment. Please inform our customer service staff that your cat requires a blood pressure measurement, and you will be shown to a quiet room, instead of waiting in the noisier waiting room.

A urine sample is usually taken from a cat by inserting a very fine needle directly into the bladder, through the abdominal wall. You may choose, instead, to collect a sample from the cat’s litterbox prior to your visit. Please ask us about the non-absorbent litter used for this collection. Samples should be collected into a sterile container and refrigerated until the visit. It should be collected the same day and be free from contaminants, especially faeces. *International Renal Interest Society